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