Carbon Fiber Driveshaft

Reducing rotating mass - or more precisely, rotational inertia - can do wonders for a car's responsiveness, and replacing the heavy steel OEM driveshaft with a lighter aftermarket unit is a common upgrade among road racers. Most opt for aluminum shafts, because they're reasonably inexpensive, but carbon fiber shafts, while pricey, offer not only the lowest inertia, but the added benefit of vibration and shock damping, as well.

After a doing bit of digging, I decided to have Mark at Precision Shaft Technologies build me a custom carbon fiber unit, and the driveshaft was already on order in 2002 when I took Taz down to the local alignment shop. It occurred to me while watching the alignment techs at work that these guys could perform a driveshaft swap in no time flat with their lifts and air tools. Back then, I didn't yet have my own air tools, so it would have taken me half a day on my back, with the car sitting on jack stands, to perform that swap. I asked the techs if they were interested in making a few extra bucks installing a new driveshaft for me. They were, and the crew at Network Alignment performed the swap in less than 20 minutes after the new part arrived.

The photo below shows the PST driveshaft following installation. In this shot, you can also see part of the Ford Racing FR500 catback, and some of the Kenny Brown Extreme Matrix chassis reinforcement components :

NOTE:  The installation of a Ford Racing T-56 transmission required the replacement of this driveshaft with a shorter  one. Naturally, I opted for a similar PST unit.

MM Clutch Quadrant & Firewall Cable Adjuster

About the time I ordered my twin-screw kit, I decided it was time to replace the plastic OEM clutch quadrant with the recently released Maximum Motorsports aluminum clutch quadrant and firewall adjuster. Like everything else I've purchased from MM, these parts were of the highest quality, and the installation instructions were excellent. The entire procedure took only about 30 minutes.

I shot no photos during the brief installation process, but here are a couple photos of the parts that I lifted from the Max Motorsports instruction sheets for them.

Taz Gets a Girdle

The Kenne Bell announcement that development would resume on a twin-screw kit for the '99/'01 Cobras coincided with a solicitation by Mark Chiappetta of Zone 5 Performance for pre-production deposits on a differential cover brace that he was developing. Mark, being the owner of one of the Eaton-supercharged Terminator Cobras, had become concerned about the rear cover failures being reported by other Terminator owners, and he decided to see what he could do to minimize the possibility of the same sort of failure occurring on his own car.

Mark had begun experimenting with a brace design that Joe Lynch had built for himself while he was still running an IRS on his '99 Cobra. Mark made a few changes that he thought might improve the part, and when he reached the prototype stage of development, he put together an attractive pre-launch group purchase, just as he had done with his MAFterburner. Since all 8.8" 1999 - 2004 Cobra rear ends are essentially identical, and because I was anticipating making somewhat more power than a stock Terminator, I jumped into Mark's group purchase with both feet. In fact, I was the sixth person to throw down a deposit, and Taz was sporting his own brace before his compressor ever saw boost. Here's a photo of the part taken from below, after I had installed it.

Doug at BilletFlow produced the part after Mark had completed his prototype testing. Also known as the IRS Girdle, this brace has been very successful in preventing broken housing covers. The brace not only performs it's job as advertised, the production part is a beautifully finished piece. In fact, it looks so good that I'm half tempted to buy a second brace one of these days and have it encased in Lucite block as a conversation piece.

2006 - 2007 Drivetrain Upgrades

Between late 2006 and early 2007, in addition to installing numerous suspension upgrades, I made extensive improvements to the Cobra's drivetrain. The teardown process to prepare the Cobra to receive all of the new parts required stripping everything from the underside of the car from the crankshaft back. By the time I had finished, poor Taz looked like a gutted animal when viewed from beneath.

Part of the teardown process involved dropping the IRS subframe, and the first of the two photos above shows the assembly (sans knuckles and halfshafts) immediately after removal. The second shot, directly above, shows the upgraded assembly ready to be reinstalled. To see what transpired between these two photos, along with details about all the other drivetrain modifications, read on. The sections below contain all the 2006 - 2007 drivetrain upgrades, beginning at the front of the car and working back.

Editorial Comment:  To all of you knuckle draggers who whined and bitched about every perceived deficiency of the '99 - '04 Cobra's IRS design, both real and imaginary, especially those of you who were actually RETARDED enough to swap your IRS Cobras over to SRA rear ends, I have just one thing to say:  DIE!!! I suppose all you beer-bellied, tattooed trailer court refugees are proud of yourselves. After all, you managed to send a clear message to Dearborn that Mustang buyers, as a whole, aren't quite ready for such newfangled contraptions as independent rear suspensions. We're only interested in going fast for very short distances in perfectly straight lines, right? Die, you MORONS!

Are you SRA guys planning to swap out those DOHC's for pushrod motors next? That's just about all that remains to complete the devolution of your cars into genuinely anti-diluvian tin, isn't it? Honestly, some peoples' kids! Just when the entire Mustang line was poised to transcend the prehistoric stick axle with which it had been cursed since its inception a half-century ago, you Neanderthals and all your carping about the IRS Cobra's shortcomings at the drag strip convinced the folks at Ford that they didn't really need to spend the money. Now, ever since the release of the S-197 platform, the IRS is once again completely absent from the Mustang landscape. Well done.

I'm not saying that I believe the Cobra's IRS, as delivered from the factory, was ideal. The design was arguably compromised by cost considerations and various corporate edicts. Nevertheless, it WAS light-years ahead of the Conestoga wagon axle with which lesser Mustangs were (and are) hobbled. Compared to a live axle rear end, the IRS offered better F/R vehicle weight balance and significantly lower unsprung weight out back. It also provided a great starting point for massaging the Cobra into a world-class handling monster.

Others have suggested that the Cobra's IRS could never be made to perform exceptionally well because of the restriction that it be a bolt-on substitute suspension for a single sub-model within the Mustang lineup. I disagree because I've personally done just that. Besides, an IRS is by nature a separate, self-contained subassembly. How it attaches to the vehicle isn't relevant. The important aspect is how well it works, and I believe SVT's suspension engineers came up with an excellent solution, especially considering the cost, NVH, and other constraints under which they labored. A bit of bushing recalibration and a few other minor tweaks, and one could have himself a great little canyon carver.

Alas, that potential came to an end with the release of the S-197. From that point forward, Mustang buyers were once again relegated to cars with stick axles, thanks, in no small part, to all of you knuckle draggers among us. Retards!

Terminator Flywheel-Clutch-PP

Although they continued to hold up fairly well after the twin-screw installation, Taz's stock clutch and pressure plate hadn't been designed to handle the torque that a force-fed Ford modular motor can produce. I began to notice some intermittent slipping behind the blower, so I was already planning on replacing the OEM parts when I fell into a sweet deal on a complete Terminator clutch kit, which also included an aluminum flywheel. Since the lightweight flywheel would assist in reducing the driveline's rotational mass, I snapped it up.

Afterward, these parts sat in my garage in their original shipping carton for more than a year and a half. But that's okay. They're car parts not foodstuff, so they hadn't "spoiled" before I got around to installing them. The reason for the delay was that I had been kicking around the idea of buying a Ford Racing 6-speed transmission for the Cobra and didn't want to replace the stock clutch until I had come to a decision, one way or the other, about replacing the car's stock 5-speed. No sense in reinstalling the 5-speed if I was going to replace it, anyway.

Eventually, I decided to add the 6-speed to my 2006 drivetrain upgrades and finished procuring all the various parts. After first removing the entire driveline, I worked my way from front to back underneath the car installing all new parts, beginning with the flywheel. Below is a photo of the new flywheel, and below that the clutch-PP assembly following their installations.

The flywheel/clutch/pressure plate swap was entirely straightforward, thanks to the Ford service manuals that my that friend Roy had given me and the technical advice, moral support, and wrenching assistance provided by my buddy Jim. Thanks, guys. You both contributed immeasurably to Taz's rather extensive 2006 - 2007 upgrades.

TECH TIP:  These cars were equipped by Ford with non-standard 11" clutch disks and pressure plates. The thickness of the OEM 11" disk is only .270" on these cars vs. the standard Ford .310" thickness, and the pressure plate was designed for this non-standard disc thickness. If you replace your clutch disc with a standard .310" thick disc, you'll need to install a shim between your pressure plate and the flywheel to enable the pressure plate to function properly with the .310" thick disk.

TECH TIP:  The installation of any clutch/PP parts that shift the fore/aft location of the pressure plate's fingers from the stock location should be accompanied by the installation of an adjustable pivot ball to enable proper alignment of the clutch fork.

TECH TIP:  I have it on good authority that McLeod manufactures the Ford Racing and Terminator aluminum flywheels and will replace their friction discs for a nominal fee (about a hundred bucks apiece). These are great flywheels. They're as light and strong as any around. If you own one with a worn friction surface, why buy a whole new aluminum flywheel when you can have yours refurbished for less than 1/3 the price?

Editorial Comment:  Tradeoffs. All things automotive involve tradeoffs, and we all have different priorities. That's why there's no "best" anything. The best choice for a dedicated track car isn't usually the wisest one for a street car. Similarly, the ideal products for road racers certainly aren't the best picks for drag racers or for anyone building a boulevard cruiser. With regard to drivelines, minimizing rotational inertia has always been the Holy Grail for road racers, but this is generally considered among quarter-milers and those in search of the smoothest power delivery to be counterproductive.

Those of us addicted to the twisties are always looking to maximize our cars' responsiveness, and removing driveline hysteresis by minimizing rotational inertia plays a significant role in that quest. Reducing driveline inertia enables our vehicles to respond more immediately to both modulation of the loud pedal and application of the brakes. But there's a down side. By virtue of their heightened reflexes, our cars become more difficult to drive smoothly in traffic. There's less spinning mass behind our motors, so they don't store up much kinetic energy to retain RPM the way heavier components will. This makes them trickier to drive. Reduced rotational inertia is a deficit for drag racers, as well, because those big clutch dumps pack far less punch with significantly lightened drivelines than they do with heavier components.

What all this boils down to is that the components you select for yourself need to match the goals you've established for your car. For most folks (anyone other than us loonies harboring fantasies of becoming the world's next great F1 superstars), heavier driveline components generally should get the nod over lighter ones when upgrading. A car with a billet steel flywheel and steel driveshaft will not only deliver a much harder hit behind a big clutch dump, it will also provide much smoother performance in stop-and-go driving than one with a lightweight driveline.

Lightweight components are desirable for only those seeking hair trigger reflexes, so don't rush out to the garage and install an aluminum flywheel just because I did. This admonition applies to every single change you make to your car. Think for yourself. Determine your own needs based on your own priorities, and map out your own path to your goals. Don't become a "parts lemming," blindly throwing parts at your car just because some yo-yos on the Internet did and claim they're the greatest automotive improvements since pneumatic tires. If you do, you'll likely end up terribly disappointed and frustrated.

Ford Racing T-56 Transmission

I spent years thinking about a 6-speed for Taz before finally pulling the trigger on this upgrade. With the OEM 5-speed, I could never shake the feeling that I was missing a gear between its 1:1 fourth and tall overdrive 5th. The 00R-spec Tremec T-56 with which I finally replaced the factory 5-speed addressed that issue by sandwiching a performance ratio short overdrive 5th (0.80) between its 1:1 fourth and 0.62 sixth. Perfect.

After spending a lot of time agonizing over the cost, I added a brand new Ford Racing T-56  transmission and crossmember to my other 2006 - 2007 upgrades. The good folks at Southwest Ford  in Weatherford, TX offered what I wanted at competitive pricing and were even kind enough to save me the shipping costs by having the parts drop-shipped directly from Ford Racing to me. Considering the size and weight of a crated T-56 transmission, that's no trivial savings.

TECH TIP:  If you are considering upgrading to a 6-speed transmission, be aware that several different T-56 variations are available, and there are numerous differences, large and small, among them. One of the biggest is gearing. Even for a motor with respectable low end grunt, a 2.66 first gear makes for a rather doggy hole shot, and a 2.66 is all the Terminator-spec transmission brings to the table. By comparison, the 00R-spec transmission (Tremec model number TUET-1260) is equipped with a 2.97 first gear, and since 2nd and 3rd gears are also shorter in the 00R, this transmission is much better suited for spirited driving.

Let's put that first gear difference into perspective:  a 2.97 first coupled to a 3.73 rear end actually provides a BETTER overall mechanical advantage than a 2.66 first driving a 4.10 ring and pinion set. Don't take my word for it; do the math yourself. What's that you say? Don't know how? No worries. Just use the Tire & Drivetrain Calculators on this site's Tech Docs page to work it out.

Although I could have had a rebuilt Terminator take-out for a whole lot less than the Ford Racing 00R-spec unit set me back, I decided to spend the extra money necessary to do it up right. Among other things, the Terminator-spec T-56 lacks both the gear ratios that I wanted and a 31-spline output shaft (the Terminator's is 27-spline). As for the even more expensive Viper-specT-56, it's geared tall, like the Terminator transmission, in first through third. And its overdrive gearing is even taller, with a 0.50 sixth gear. If you're making HUGE torque and/or have an extremely short rear end, like a 4.56, then a Viper-spec may make sense for you, but its only real advantage over the 00R-spec unit is its enormous torque capacity. And with the advent of the T-56 Magnum, you no longer need to sacrifice gearing for torque capacity, so why bother?

As you can see in the photos below, the new T-56 bellhousing bolted right up, as did the transmission and new crossmember. Some New Edge Cobra owners have reported having to clearance the passenger side of the transmission tunnel to fit a T-56, but I did not experience any fitment problem with my new tranny. I guess all the assembly line tolerances just stacked up in my favor on this one.

As for energizing  the T-56's REVERSE lockout solenoid, by the time I got around to bolting up the new transmission, I had already installed a switched 12V circuit and wired it through a momentary contact button in a new shift knob, so the REVERSE lockout circuit was handled. The only unforeseen issues that I ran into during the transmission swap were that (1) the bosses for the wiring harness's push pins were spaced differently on the new transmission from those on the TR-3650, and (2) the sending unit for REVERSE was located on the passenger side of the new 6-speed, as opposed to its driver side location on the 3650.

Not a big deal. It was easy to alleviate the first issue by removing some of the wrap from the wiring loom, moving the push pins to the correct locations, and re-wrapping the loom. To address the second issue, I split the REVERSE circuit wires out of the wiring loom far enough back to enable them to reach the new location. Then, I finished up the electrical work with some fresh flex loom and a complete wrap with some Stretch & Seal self-sealing silicone tape. (Incidentally, if you haven't yet tried this tape, do yourself a favor and pick up a roll to try out. It's pricey, but it's light years ahead of any vinyl electrical tape. In the Phoenix area, the stuff is available from both AutoZone and Home Depot.)

TECH TIP:  Here's a tip for you regarding transmission fluid. If your car's T-56 tends to be notchy or balky when shifting or refuses to shift smoothly at high RPM, and it was manufactured after 1999, try switching to Pennzoil Synchromesh, available at many auto parts stores for about $7 per quart. I have switched over to Synchromesh in my T-56, and it made a dramatic improvement in smoothness when shifting, particularly when the transmission is cold. If your transmission was built before 1999, you might want to investigate further before switching. Some of the older T-56 units use blocker rings that don't take kindly to the Synchromesh formulation.

I realize that there's a big orange sticker (visible in the photo above) on the driver side of my transmission that advises using only DEXRON III fluid, but I've contacted Tremec directly to ask what the manufacturer recommends. I received the following reply to my inquiry (the emphasis is mine):

"Thank you for your interest in the Tremec product line. I am sure that you are enjoying your new T-56. We recommend the Synchromesh fluid produced by Pennzoil. This is the best fluid to use in your transmission. Please contact us if you require further assistance."

For years, there has been an ongoing debate regarding (1) which alternative fluid might be better than Dexron III, (2) whether or not the use of an alternate would result in accelerated wear or premature failure, and (3) if any of these alternates is endorsed by Tremec. The reply I received answers all those questions very succinctly. Yes, Dexron III is still listed as the recommended fluid for the T-56 on Tremec's FAQ page at the company's website, and has been so listed forever. Of course it is. That recommendation makes sense politically. (Think about it.) The reply I received is the straight scoop from a technical, rather than political, standpoint.

One last point:  many believe that the Pennzoil and GM Synchromesh formulations are identical. They are not, and Pennzoil will tell you they aren't if you care to ask. Here's the response another Synchromesh user received in response to his question about the interchangeability of the formulas (again, the emphasis is mine):

The synchromesh fluid that Pennzoil-Quaker State makes meets the warranty and performance requirements of the GM 12345349 part number for your application. It is not the same fluid that is in the GM synchromesh fluid package, so you can make your purchase choice based on price if you choose. If you have any other questions or comments, please contact us at 1-800-458-4998, M thru F, 8am to 5pm, CST.

So there you have it, straight from the horse's mouth. No hearsay, no guessing, no Oji board messages from beyond the veil. They're different formulas. I have no firsthand experience with the GM formula, so I cannot say whether or not that product offers any advantage in a T-56 transmission. I bought the Pennzoil formula, as recommended, and have no intention of spending significantly more money for the GM product until I have it on good authority that it is even better.

MGW Shifter

The shifter supplied with the Ford Racing T-56 was about the same quality as a stock TR3650 shifter. Feel free to draw your own inferences from that statement. I had been very happy with the Steeda Tri-Ax that I had used with my 3650, except for its uncanny ability to transmit noise, so I was planning on picking up another Tri-Ax for the new T-56. However, my friend Roy had switched to an MGW shifter and suggested that I try one of those with the T-56, so I did, and I'm genuinely glad. I've heard that the T-56 is extremely noisy with a Tri-Ax, but my transmission is very quiet with the MGW. More importantly, the MGW's unique design enables me to position the handle exactly where it works best for me. George and the crew at MGW get two thumbs up for this one. This is what the shifter's base looks like when bolted to the T-56:

Circled in red above is the transmission's shift detent bolt. Many owners insert one or two copper washers here to relieve detent pressure for easier shifting. I have not yet tried this modification, but my friend Jim has performed this modification on his D&D Viper-spec T-56, and likes the results. I will reserve judgment until after I have driven his car.

The photo below shows the OEM outer boot being fitted to the MGW riser during installation. (Pay no attention to the rat's nest of non-standard electrical harnesses around the shifter.)

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Tech Tip:  When installing any aftermarket shifter on a T-56, remove the shifter's Stop Bolts. The T-56 doesn't need them, and leaving them attached to the shifter can damage the transmission if the bolts aren't backed out far enough. You don't need to accept my word with respect to this advice. Here are a few words directly from the transmission manufacturer's website (the emphasis is mine):

"The major problem with aftermarket shifters is that they have stops on them. To install them correctly, you will have to remove the stops completely. Our transmissions are built with internal stops."

That should be clear enough for even the most intellectually challenged out there in Internet Land.

Here's a shot of the completed shifter installation, including a MOMO airmetal & leather shift knob (to match the previously installed E-brake handle). The knob has been modified with the addition of a REVERSE solenoid momentary-contact pushbutton top center. This knob bears no shift pattern, so to address those rare occasions when I am forced to allow someone unfamiliar with Taz to pilot him, I added an aluminum placard containing the T-56 pattern to the base of the center stack, just beyond the billet shifter bezel.

2011 Update:  MGW eventually released a handle considerably shorter than the orange one with which my shifter was originally supplied. I've always preferred the shortest throw shifter I could find, so I decided to try one, and I genuinely love it. As far as I'm concerned, the MGW shifter with a silver handle is as near to perfect as any shifter has ever been. By the same token, I'm endowed with the "classic" Italian physique of relatively long arms and short legs, which makes every gear an easy reach for me when the seat is adjusted properly for good pedal work. Your mileage may vary. Depending on your build, the silver handle may not be a good choice for you.

Here are a few photos of the orange and silver handles side by side. These photos graphically depict the physical differences between the two much more dramatically than the stock photo on the MGW website. The specified 1/2" difference in length doesn't sound like much, but when you see it in relation to the overall size of the piece, the significance is readily apparent.

Of course the most important difference between the two parts is the difference in the lengths of their throws from gear to gear. I measured both and created the chart below for reference. Note that even with the handles rotated to the 7-o'clock position on the shifter's post, switching from the silver handle to the orange handle increases the throw by 12.5%. That is significant, and with the handles adjusted to the 6 o'clock position, the difference grows to 1/2", or 16.67%.

Second Carbon Fiber Driveshaft

Before I ordered my 6-speed transmission, I had heard that it was possible to upgrade a New Edge Cobra from the OEM 5-speed to a T-56 without replacing the original driveshaft with a shorter one, despite the T-56 being about an inch longer. The limited movement of the carrier in the IRS supposedly made this a possibility, because the slip tube requires practically no play in this application, and the center-to-center distance between the U-joints was short enough to enable the driveshaft to fit. All that was typically necessary was to lop off about 3/4" from the end of the slip tube to ensure that it didn't bottom out inside the transmission's tailshaft.

Encouraged by this information, I ordered my T-56, without really considering the fact that I no longer had an OEM driveshaft. My PST driveshaft had been custom built and was slightly longer between the U-joints than the OEM part had been. The PST no longer fit with the new tranny bolted up, and it couldn't be shortened due to its construction. On the other hand, considering how flawlessly my PST had performed, I wasn't about to settle for a lesser unit, so I called Mark at PST and asked him to hook me up with another driveshaft just like the one I had, except built to fit a Terminator.

The new shaft was beautiful - a perfect blend of art and technology. Kudos to PST. Mark built exactly what I had asked for. Unfortunately, even though I knew long before I ever picked up the phone to order the new D/S that a Terminator T-56 is equipped with a 27-spline output shaft, while my 00R-spec Ford Racing transmission had been built with a 31-spline output, I asked for a "driveshaft for a Terminator," so that's what I got. This "senior moment" worked out to a roughly $100 mistake. Not so bad in the scheme of things, considering the overall expense for this round of upgrades. Anyway, rather than ship the driveshaft all the way back to PST for Mark to retrofit with the correct slip tube, I had the capable folks at Arizona Driveshaft Service (back then, it was Mesa Driveshaft) install the right part.

Below, you can see my second carbon fiber DS bolted to the Terminator pinion flange on the new differential (detailed below). At least the driveshaft's companion matched up with my new pinion flange, thanks to a glitch in the Ford parts system. More on that later.

As you can see, I no longer need a wobble socket or a gear wrench to turn the 12-point bolts securing the companion to the pinion flange, because the bolt hole spacing is much wider on the Terminator flange than it was on my stock '01 Cobra flange.

TECH TIP:  For the smoothest transmission of power and maximum U-joint life in an IRS car, the pinion angle should be set equal and opposite to the angle of the transmission's tailshaft. The engines and transmissions in these cars are usually installed with the transmissions tilted down by about 3 degrees (-3 degrees). If your car is typical, your pumpkin should be adjusted to present a 3-degree angle up. However, your car may be atypical, so use an angle finder to obtain exact measurements. Use shims, where necessary, to adjust the angles so they offset each other within a degree or less.

Ford Racing Gears & Torsen T2R

Although the 00R-spec T-56 is endowed with a shorter first gear than a Terminator T-56, its 2.97:1 first is still a bit taller than the 3.37 first gear of the TR-3650 transmission. After installing the twin-screw, I had been very happy with the way the car pulled in first with the 3650 and stock 3.27 ring and pinion gears, so I wasn't looking for any more gear in first, but I wasn't crazy about the idea of any less, either. New ring and pinion gears were in order. My trusty gear calculator indicated that a set of 3:73's coupled to a Ford Racing T-56 would offer identical overall gearing in 1st and somewhat shorter gearing in 2nd through 5th than the original ring and pinion had provided with the 3650. That was exactly what I wanted.

My buddy Jim offered to purchase the gears for me and set them up, along with the new Torsen T2R differential that I had purchased, in exchange for a fiberglass hood he wanted that was sitting in my garage. I had no real need for the hood, so I jumped at his offer. In the photo below, you can see the new ring gear and differential installed in a second 8.8" housing, which Jim was also kind enough to provide.

TECH TIP:  If you ever have occasion to order a new 2001 Cobra pinion flange, you should be aware that you may end up, instead, with a Terminator pinion flange, as I did. Although my new part came in a box bearing a Ford Parts label that read "2001 Cobra," that simply wasn't so. There apparently is - or at least was at that time - a glitch in the Ford parts numbering system, as others have reported the same experience, and one of the guys at Southwest Ford told me that his parts catalog listed the same part number for all Cobras from 2001 through 2004. This is incorrect, but not necessarily a bad thing. Not only are the Terminator flanges stronger than their '01 counterparts, but the runout issues that had plagued the '99 and '01 parts have been absent from the newer ones, as well. Nonetheless, to fit the larger pinion flange, you will also need to install a newer style companion on your driveshaft if you have been running the smaller one.

With respect to the above Tech Tip, the part number snafu turned out for the best in my case, because my second PST driveshaft had been constructed to mate with a Terminator pinion flange. The photo below shows the new pinion flange installed along with a Paul's High Performance pinion brace and poly front bushings for the 3rd member. Naturally, when I installed the PHP bushings in front, I also swapped out the housing's rear bushing for a Max Motorsports poly replacement to avoid a large durometer difference between the front and rear.

Editorial Comment:  I have heard and read opinions maintaining that polyurethane is unsuitable for use as a bushing material for the mounts on the differential housing of an IRS Cobra. The conjecture is that poly is too susceptible to heat breakdown, and that Delrin is better suited for use here. Let's consider this notion. The OEM Ford bushings are rubber, and the specified continuous high temperature operating limit of the type of rubber used in automotive bushings ranges from 220F to 250F degrees. However, polyurethane's operational upper bound can run as high as 275F, depending on formulation. By comparison, the Delrin material of which some appear to be so fond has a specified continuous high temp operational limit of only 185F degrees, nearly 100 degrees BELOW polyurethane's upper bound! Bear in mind that all these temperatures are the specified continuous SAFE OPERATING limits for these materials, not their melting points. Automotive rubber and poly bushings have melting points around FOUR HUNDRED degrees, give or take a few. Delrin's MP is 350F.

Obviously, pumpkins hot enough to break down poly bushings are more than hot enough to destroy OEM rubber bushings, as well, and Delrin wouldn't stand a chance. So Delrin is certainly NOT a more suitable material from a thermal standpoint. What's that you say? Delrin is recommended for only the housing's rear bushing, which somehow remains COOLER than its front bushings? Right. The notion that the housing's front bushings are subjected to higher operational temps than the back one is shear nonsense. The pumpkin's front mounting ears and bushings are wide open to a cooling flow of air, as you can clearly see in the photo above. The rear bushing receives relatively little airflow and is completely encased in a steel sleeve that transfers conducted heat directly from the housing's cover. So the rear bushing remains cooler than those in front by ... MAGIC?

"Much louder. REALLY LOUD above 75mph. Would not want to take this car on road trip."

That's a real quote from a less-than-ecstatic new owner of solid differential bushings, and his experience is not uncommon. Here's one of the replies he received:

"Yup. Did the same mods as you, and still had the hop and lots of gear noise."

Many other replies ran along this same vein. Of course, the Internet tough guys who sully up the forums with their relentless intimidation don't really care about that sort of thing, so don't expect any sympathy from them after you follow their BAD advice. One tough guy made the following rude and arrogant remark in response to the complaint:

"These aren't luxury cars, if you want a quiet ride go buy a Caddy!"

Gee, that seems like a rather extreme fix, doesn't it? How about simply replacing the ill-considered solid bushings with a little more compliant material, like poly? Gotta love those Internet tough guys - just chock full of sensitivity, as well as great ideas for enahancing your driving enjoyment. NOT!

After I began open-tracking my Cobra, I noticed that the pumpkin had started spitting a bit of gear oil out its vent tube, and a little oil had begun to seep out between the case and the cover. These were clear indicators that the OEM Trac-Lok was getting too hot on the road course, and I needed to do something about it before things got worse. I had heard and read so many positive reviews of the Torsen T2R Racemaster with respect to its on-track performance, reliability, and consistency that I added one to my 2006 - 2007 drivetrain upgrade list. Years later, my T2R continues to live up to its reputation, so I have been very pleased with my choice. The Torsen is a worm gear, constant mesh, limited-slip differential. Although the T2R's web page description mentions that some applications use clutch plates, and clutches are even depicted in the exploded view on that page, the T2R manufactured for the IRS Cobra is not equipped with clutches, so it requires no periodic maintenance other than oil changes. Much more importantly, the Torsen runs significantly cooler than the Trac-Loc it replaced - cool enough that I don't feel the need to add an external diff cooler for road course duty. If I were racing the car, I'd probably add a cooler, just to be safe, but OT driving isn't demanding enough to require one with this differential.

TECH TIP:  Although any 8.8" carrier for a Ford will fit in an IRS Cobra's pumpkin, it's safest to use one specifically designed for the IRS. The side gears of an IRS-compatible differential have been machined with grooves for the snap rings on the inboard stubs of the halfshafts. A differential built for a stick axle car won't have the retention grooves, which means there will be nothing other than your axle nuts securing your halfshafts in place. Not a good idea. You should be able to install an IRS carrier in an SRA vehicle without issue, but you shouldn't swap the other way around without first having a shop machine the side gears with snap ring grooves.

Time for a quick word about gear lube. My differential gear oil of choice ever since I began participating in autocross and open track events has been Red Line Lightweight Shockproof. Shockproof is a unique gear lubricant containing microscopic graphite particles in colloidal suspension to provide reduced drag and enhanced protection. The "lightweight" formulation is comparable to a 75W140 conventional gear lubricant, which is what both Ford and Torsen recommend. I've been filling my pumpkin with this gear oil for some time, and the Shockproof formula has performed admirably despite the extremely harsh track conditions to which the car is periodically subjected. Nevertheless, this lubricant should be AVOIDED by those who run differential pumps, coolers, or filters, because its affinity for metal could result in clogging of those components. Consider yourself warned.

DSS Level-5 Halfshafts & Hubs

Having read numerous accounts of broken OEM halfshafts, I felt uncomfortable about continuing to run them after significantly bumping the torque capabilities of the Cobra by adding the twin-screw supercharger, so I decided to upgrade to a pair of  Level-5 halfshafts from the Driveshaft Shop. Although the L-5's admittedly are overkill at Taz's power level, you can never tell what the future may hold, and a project car is never really finished, is it? Besides, the L-5's are actually a few pounds lighter than either the OEM units or the DSS L-2's, because the L-5 axle bars are manufactured from 300M steel, and so can be made with less material. (Because of its very high strength, 300M is also used for such applications as aircraft landing gear, high strength bolts, and airframe parts.) In the photo below, you can see the difference between a stock '01 halfshaft (top) and a DSS Level-5 fitted with a Terminator inboard CV and stub. Note that the diameter of the L-5's axle bar is considerably smaller than that of the OEM's. Also note that the outboard stub of the L-5 is much stouter than the OEM's. This is why the L-5's require custom hubs, which are included with the axle purchase.

My L-5's didn't ship with inboard stubs or inner CV joints, and I couldn't reuse my '01 inner CV's with the DSS axles, because they wouldn't mate up with the new axle bars. At the time, DSS didn't even offer the halfshafts complete end to end. L-5's are now available either with or without inner CV's, but I was required to track down a pair of Terminator inboard stubs and CV joints in order to complete mine, as was everyone else back then. I picked up my inner stubs from a misguided soul who was switching his Cobra to an SRA setup. His loss; my gain.

TECH TIP:  If you're in the Phoenix metro area, and you ever require service for either your steering rack or your halfshafts, I recommend Phoenix Rack and Axle to assist with your needs. After a brake hose rubbed through the outer boot on one of my axles, the folks there were kind enough to reboot the axle while I waited. Friendly people, first-rate service, and great prices - what more could a fair-haired lad ask of any business? Phoenix Rack and Axle also offers a number of other driveline services, including driveshaft balancing and custom work. Give 'em a try. You'll be glad you did.

Although they didn't ship with inboard stubs, my L-5's did ship with a pair of DSS billet steel hubs and a couple sets of ARP wheel studs. The reason for the new hubs is that, as I mentioned above, the L-5 outboard stubs are much stouter than the stockers, with a higher spline count, so the OEM hubs can't be used with them. The photo below shows the DSS billet hubs already pressed into the OEM knuckles along with fresh Ford # 39DZ-1215-A wheel bearings, which were contributed to the effort by my friend Roy, who just happened to have an extra pair lying around.

I pressed fresh wheel studs into each hub prior to installing the hub in its knuckle. DSS provides stout 3-1/2" ARP wheel studs with the L-5 hubs to enable the assembly to pass NHRA track tech, which is great for those who must conform to the NHRA rulebook. But for aesthetic reasons, folks like me who don't need to meet those tech requirements would typically rather not run long studs and open lug nuts. Unfortunately, Ford OEM studs can't be substituted, because their .615" knurls are too small for the stud holes in the DSS hubs, which have been cut larger to accommodate the supplied ARP parts.

I originally planned on simply having the ARP studs cut down to a suitable length for use with the factory lug nuts, but after doing a little digging, I discovered that Moser manufactures Grade 8 wheel studs in the same 1.75" length and 1/2"-20 thread pitch as the OEM studs, but with a .625" knurl diameter that would fit the DSS hubs. Score! The Moser studs are the ones you see pressed into the hubs in the above photo. Look for Moser part number 8368 if you'd like a set of these.

TECH TIP:  The correct method for installing wheel studs is to press them into the hub. The gang over at the Mopar Action website caution that pulling studs in with a nut and some flat washers will almost certainly result in over-torquing both the stud and the nut. I concur. In the absence of a press, driving the studs in with a drift and BFH is a suitable stud installation alternative, but pulling them in will weaken them, increasing the possibility of failure. Feel free to ignore this advice as you see fit. The world could certainly do with fewer ignorant, pigheaded people.

If you'd like to have annotated copies of Taz's 2006 - 2007 driveline and suspension upgrade installation photos, including the photos you see above, just right click the link below and select the "Save Target As ..." or "Save Link As ..." option from the fly-out menu that will appear. This is a fairly large file (more that 5MB), so it may take a minute or so to download, but that's still preferable to the delays you would otherwise encounter trying to view the file in place via the Internet.

2006 - 2007 driveline & suspension upgrade installation photos (PDF)

Editorial Comment:  I've read a number of negative remarks on the Mustang forums about the DSS L-5's. Most of those comments were posted by clowns without the benefit of even secondhand experience with the product, much less any firsthand experience. While it's true that DSS products have had issues from time to time, just like most other products, it's also true that Frank has done his best to offer a mutually equitable solution in every case. The facts of the matter are these:  (1) the vast majority of L-5's have never suffered from any problems, and (2) remediation has been provided - or at least offered - for those few that did. Unfortunately, it's always the squeaky wheel that gets the grease, isn't it? And some wheels just won't quit squeaking, regardless of what you do.

Face it. No product of any consequence is ever 100% problem free, so all that separates the best manufacturers and vendors from the rest is how they respond when issues do arise. Although I bought my L-5's in 2005, I delayed installing them until I was ready to perform all of my other drivetrain upgrades in December of 2006. Consequently, I didn't discover that there was an issue with one of my DSS hubs until a year after I had purchased them. I am pleased to report that Frank at DSS took care of my problem by replacing BOTH hubs with a brand new pair. You gotta love a man who stands behind his product like Frank did for me, and I always make it a point to let folks know about it whenever I run across people like Frank, just as I always report my experiences at the other end of the spectrum.

All the DSS bashing that you may have read on various forums notwithstanding, I can tell you that my personal FIRSTHAND experience with DSS has been extremely positive. Furthermore, I've been running my L-5's for years now, including numerous autocross and open track events, and I'm still waiting for these halfshafts to destroy my spindles, as has been suggested would happen by now. Gee, do you suppose that's just not going to happen? Do you suppose maybe all that fear mongering is a lot of Chicken Little nonsense perpetuated by a bunch of fools? I do.

Of course, failing to dissuade potential L-5 buyers with slanderous epithets, the Internet DSS-haters invariably fall back on their tired old "overkill" augument. "You're wasting your money ... You don't really need those ... They're overkill ..." Hmm. And the point of those remarks is ... WHAT? After all, overkill is exactly what I shoot for with every single upgrade that I perform on my car. I don't know about you, but I'm inclined to replace EVERY part I remove with a new one of higher quality, and the more critical the part, the more performance headroom I shoot for in the replacement. Breaking a halfshaft can be downright dangerous in any situation, and very likely fatal when pushing the envelope. Kissing Firebird Raceway's grandstand wall at 100+ after twisting an axle in two is a Kodak moment I'd prefer to not experience, so count me all in for a pair of L-5 axles.