Steve Baur
Former Editor, Modified Mustangs & Fords
May 4, 2007

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Project Stolen Goods, our resident '93 Cobra, is coming along nicely, as we have installed a Road and Track suspension package from Maximum Motorsports, an Extreme Plus braking system from Baer, and FR500-style wheels from American Muscle with Falken's new RT-615 competition street tires.

While our Boss block-based powerplant is off being machined and assembled, we thought it was the perfect time to sort out the transmission and other driveline components that will back our project car in its quest for corner-carving chaos.

All '93 Cobras were equipped with a T5 five-speed transmission from the factory, and while the gear ratios were carried over from the standard 5.0 H.O. transmission, the cluster gear received a phosphate coating for greater strength. A roller pocket bearing was also employed between the input and output shafts, which dictated different input and output shafts, among other things. The Fox-bodied snake also utilized a different clutch than the H.O.-powered ponies, one that was stronger in its holding capability yet easier to actuate.

Big surprise, we have neither of these two items, and if you have to replace something, you might as well upgrade, especially when the motor ahead of these items is going to produce nearly double the factory output. Replacing these items allows us to take advantage of the years of technological improvement that has occurred since the Cobra came off the assembly line.

Components used in Stolen Goods A-5 transmission include the Astro Performance A-5 Gear Kit (First through Fourth), the 0.79 percent overdriven Road Race Fifth Gear Kit, the mainshaft, the cluster support plate, the First/Second and Third/Fourth shift lugs and solid selector, the steel bearing retainer, and the master bearing/ synchronizer and ring/seal kit. Got torque? These upgraded A-5 components can handle 500-plus lb-ft of torque.

For Stolen Goods, we opted to stay with the Tremec T5 transmission, as our eventual power output did not dictate a need for a beefier unit. The T5 is also lighter than most of its competition in the market, which is a good thing since we already added several suspension parts (weight) that didn't come from the factory.

We weren't going to use just any T5, though, so we took a well-used unit we had lying around and dropped in on Astro Performance Warehouse in Tavares, Florida. Astro owner, Tony Sarvis, explained what transmission parts tech Gerry Hoffman would install in our unit.

After dismantling our gearbox, the Astro crew decided we needed one of its A-5 gear kits ($1,150), as well as its 9310 alloy output shaft ($365) and billet cluster support plate ($45). Since we planned to road race the Cobra, Sarvis recommended we use Astro's 0.79 Overdrive ($200), which would keep the revs higher when shifting into Fifth on long straightaways.

Obviously, Astro sells its transmission components separately, along with any factory/ OEM transmission parts you might need. Since the A-5 gear kit and components fit into the OEM T5 case, you can utilize OEM bearings and synchronizers. Astro also offers the A-5 Gear Kit for '94-up Mustangs and 3.8L six-cylinder models.

Customers can either purchase an '85-'95 Mustang 5.0L T5 and build up the transmission with the upgraded components, or simply buy one that Astro has already assembled. If you plan to buy one that Astro has built, a core exchange is required, unless you purchase a brand-new A-5.

The Astro A-5 five-speed transmissions for the 425-lb-ft of torque/550hp version starts at $1,650 with core exchange, while the A-5 525-lb-ft of torque/650hp starts at $1,995 with core exchange.

This is the Astro Performance A-5 input shaft (top) vs. factory/OEM shaft (bottom). The A-5 input shaft is available in two Mustang lengths: one for '85-'93 5.0L Mustangs and the other for '94-'95 5.0Ls. You'll need to change out your clutch disc due to the 26 splines on the A-5 input shaft.

"Most people complain that the aftermarket five-speed 'replacement' transmissions for the T5 are heavy, require too much modification, and don't shift well above 5,600 rpm," Sarvis says. "The A-5 gear kit and components closely address each of these items, as the T5 weighs approximately 83 pounds with fluid, has a "centerline" distance from input shaft to the top cover almost equal to that of the earlier Top-Loader four-speed trans-mission, and can be shifted comfortably up to 7,000 rpm with proper clutch adjustment."

Other features of the Astro A-5 five-speed transmission include use of the factory '85-'95 Mustang 5.0L bellhousing, shifter, transmission mount and crossmember, and driveshaft. The only required modification is that you'll need to swap out the factory 10-spline clutch disc for a 26-spline version to match the A-5 input shaft. The 26-spline input shaft used in the A-5 gear kit will not "twist" the splines as will a factory/OEM 10-spline when used in higher-horsepower vehicles.

The A-5 cluster gear (top) not only has larger gear teeth than the factory/OEM cluster, but it's also a three-piece design, which means that in the unlikely event of a transmission failure, the cluster shaft can be pressed apart to replace any one gear that may be damaged. Astro has plans to develop other ratios to allow the customer to change out a couple of gears in order to change the ratio, not the whole gearset.

Astro developed the gear kits' ratios around customer needs/wants, so it utilizes a 2.95 First-gear ratio, which allows for a longer in-gear duration, which is beneficial to cars running lower rearend ratios like 3.73, 3.90, and 4.10. The Overdrive from any T5 "World Class" transmission from an '85-'95 Mustang 5.0L can be reused with the Astro A-5 gear kit to provide a more fuel efficient 0.59-percent Overdrive, or if you need to tighten the gear spread, Astro also stocks an A-5 0.79-percent Fifth-gear kit.

We'll need a clutch to transfer power from the engine to the new transmission, and with our horsepower goal of 400-430, there are numerous clutches on the market that could serve our need. Since Stolen Goods is going to be naturally aspirated, we want to make the drivetrain as efficient as possible, so we called Centerforce Clutches and ordered one of its LMC Series clutches with an aluminum flywheel. The LMC stands for "light metal clutch" and is a specifically designed, low-inertia performance clutch that reduces engine rotating mass. These lightweight, SFI-approved competition clutches are intended with most road racing and circle track applications in mind, which is right up our alley.

To make sure Stolen Goods' rpm doesn't drop significantly while speeding down the back straight, Astro Performance used its upgraded 9310 alloy steel 0.79 percent Fifth gear. Another option, though not as strong, reuses the factory Fifth-gear kit from an '85-'95 Mustang 5.0L, to achieve a 0.59 percent Overdrive, which is a bit more fuel efficient than the OEM 0.68 percent.

Centerforce machines these special pressure plates from high-strength, aircraft-grade billet aluminum and then attaches a special heat-treated, replaceable friction surface. The Centerforce LMC-series friction disc utilizes a dual-segmented, carbon-composite lining for improved cooling and excellent torque capacity. Another feature of the LMC is its patented ball bearing-actuated diaphragm and centrifugal weight system, which allows for maximum grip while maintaining a comfortable and controllable clutch pedal. We'll delve more into the clutch technology once we get ready to bolt the drivetrain together in a month or two.

The last link in our drivetrain is the driveshaft, and for this we simply went with a Ford Racing Performance Parts aluminum unit. We called Texas Mustangs Parts in Waco, Texas, as we knew it carried the bulk of the Ford Racing catalog. The driveshaft will bolt right in, and we'll be good to go. Hmmm, do we have driveshaft bolts?

Next month, we plan to bring you the first part of the engine buildup, where we'll show you the features of FRPP's Boss block, along with the modifications and machining that D.S.S. Racing will perform on it. Until then, read on about the stout gearbox that Astro Performance has assembled for project Stolen Goods.

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