Astro Performance assembles a road-race-ready, but streetworthy T5.
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.
Notice the wider and thicker teeth of the A-5 First gear (left) vs. the factory/OEM First M/S gear (right). Astro claims that the A-5 First gear is the strongest synchronized First mainshaft gear on the market. It also converts the factory First-gear ratio to a 2.95 from a 3.35:1. | 
The A-5 Second gear (right) is a 1.95 ratio and is just as beefy as the rest. Compare it to the tiny OEM Second M/S gear (left). | 
Notoriously prone to failure in most T5 World Class transmissions is the stock third gear. The Astro A-5 Third gear is a 1.36 ratio piece (right) that is manufactured out of the same premium-alloy 9310 steel as First, Second, Fourth, and Fifth. |