Muscle Mustangs & Fast Fords
1988 Ford Mustang Cobra - Five Functioning Forward Gears…
...and a broken rearend.
If you drive your car hard, broken parts are inevitable. If you go to the track regularly or drive your car in anger, you will eventually find the weak link in your combination. Downtime and the expense of replacing hardware thoroughly sucks, so we always recommend installing the best, and strongest components that you can afford.
Last month, we buttoned up some odds and ends on our Three-Valve Fox project and headed to the track. With the engine firing on all cylinders, we laid down a mid-12-second quarter-mile time, while not cleanly negotiating all of the gears in the high-mileage T45 transmission. The end result was a best e.t. of 12.63 at 108 mph, a broken T45, and a majorly disappointing ending to our track outing.
After limping home, the transmission debate started. Some said go auto; some said stay with a stick. All had valid reasons, which made the decision a tough one. In the end, we opted to rebuild the T45.
We began looking for rebuild kits that would allow our T45 to handle a significant amount of power. We contacted American Powertrain, which offered its Patriot T45Plus, designed to handle 500hp and 430 lb-ft of torque. But when we spoke to Gray Fredrick of American Powertrain, he had another idea.
"Tremec acquired parts of Borg-Warner in the late '90s," explains Fredrick. "It kept the T45 in production for the Mustang until 2000. In 2001, Tremec supplied Ford with a the TR3650 as a direct replacement for the T45."
When it came down to it, there is no logical reason to built a T45 when the 3650 is readily available and is simply a better transmission. Factor in that Tremec still makes parts for the 3650 and the decision was an easy one. Once we decided to go with a rebuilt TR3650, the next step was to find a core. A call to MPS Auto Salvage in Statham, Georgia, netted us a solid one from a New Edge GT.
Once at American Powertrain's facility, the gearbox was completely stripped and inspected. Any damaged or worn parts were replaced, and the trans was reassembled with new parts that allow it to handle massive amounts of power.
For our build, we're upgrading to one of American Powertrain's Patriot 3650Plus Extreme units, rated to handle 700 hp and 600 lb-ft of torque. The build includes new bearings and seals; carbon fiber synchros; hardened dual fork pins; new small parts kit; 1⁄2-inch and 3⁄4-inch Gorilla shift forks; solid billet keys; and a dual base-welded, Cryo-hardened, 26-spline input shaft. We also installed an American Powertrain's Science Friction Street Slayer clutch and White Lightning shifter.
To finish the drivetrain upgrade, we contacted Axle Exchange in Fairfield, New Jersey, for a driveshaft that would handle abuse at the track along with the street miles we intend on putting on our Three-Valve Fox. It supplied us with a 4-inch, aluminum shaft with upgraded yolks in the correct length for our odd build. After giving Axle Exchange all of the measurements, we were supplied with a shaft that fit perfectly.
With everything back together and some light miles to break-in the clutch, we headed to Bradenton Motorsports Park for some quarter-mile action. Before the trans swap, our Three-Valve Fox laid down a 12.63 at 108 mph, with us missing Third before the T45 let go. As we pulled the car into the burnout box for the first time, we were hoping to drop a couple of tenths by simply getting through all the gears. We were rewarded with a 12.17 at 112 mph on the first pass!
Seeing a low 12-second run without really launching or driving hard gave us faith that an 11-second pass wasn't out of reach. Unfortunately, it wasn't meant to be. After launching, it made some horrible noises and we were forced to park our Pony.
Once it's back in the shop and we tear it apart, we'll make it stronger and try to break (pun intended) into the 11s.