When we took delivery of project Stealth Bomber, the '89 Diplomat police car, we set a goal that would require a fairly stout drivetrain. The first item on the agenda is the transmission. Even though the mileage was remarkably low, the 58,000 miles showing on the odometer were hard miles. The shift quality wasn't great, resulting in early and soft shifts. This, as well as lots of overlap, and a propensity for freewheeling in reverse until the car was good and ready to move, told us it was definitely time for a rebuild. Normally, we would lean towards the more bulletproof 727, especially in a drag application where repeated hard launches take their toll, but in this situation the A999 derivative of the venerable 904 was deemed more than adequate. Remember, our stated goal is a 150-mph capability, so we will maintain the ultra-high 2.94 rear gear, and upon launch the car will not be subjected to much shock. The '89 A999 our police car was equipped with is a wide-ratio transmission featuring a 2.54:1 first gear ratio, a 1.54:1 second gear, and a 1:1 high gear. An autopsy revealed burned high-gear/reverse clutches from overheating, burned bands, and a slightly-mangled, lower/reverse drum thrust-washer. We were fortunate that our 'Flite didn't require any "hard parts," as everything internal was serviceable.
Here it is, an A999 wide-ratio,...
Here it is, an A999 wide-ratio, 3-speed automatic-slightly used, a bit grungy, but perfectly serviceable.
TransGo provided us with a...
TransGo provided us with a shift kit to help firm up the shifts on our worn-out A999 trans. This kit covers all 904 Torqueflites and their derivatives, including the A500 four-speed, automatic-overdrive units. Included with the kit was this video that shows you how to install the kit from start to finish. It proved invaluable.
Converting Torque Project...
Converting Torque
Project Stealth Bomber has some unique requirements in the torque converter department. We wanted a bit of stall in order to move the less-than-svelte Diplomat off the line with some authority, yet we wanted it to lock up tight on the top end. Having used Continental Converters with great success on past projects, we turned to owner Kris Abrahamson for help with our "unrealistic" goals. We didn't need an off-the-shelf unit, we needed a custom piece to satisfy our performance needs. We brought Kris a slightly-used A500 high-stall converter from an '89 Shelby Dakota we owned nearly a century ago. It differs from other 904-type converters in that it has a high-stall stator inside. This unit was deemed the best foundation, and Kris began by back-cutting the stator to raise the stall a bit more, adding Torrington bearings and a stronger pump drive.
Once all the mounts, linkage,...
Once all the mounts, linkage, and brackets are removed, then remove the plate on the tailshaft housing that covers the snap ring. Having access, open the snap ring and lift the tailshaft housing off.
With the pan out of the way,...
With the pan out of the way, the valvebody is now accessible and can be detached with 10 torx-headed bolts. Hopefully, you drained the trans prior to removing the pan!
With the six bolts holding...
With the six bolts holding the front pump in place removed, you will need a slide hammer to actually take the pump out of the case. There are two 3/8-inch coarse-threaded holes, 180-degrees apart at the 11 and 6 o'clock positions (approximately), made specifically for the slide hammer. After the pump is out, you can now remove the input shaft by grabbing hold and pulling-as long as the forward clutches aren't welded together. Thankfully, ours weren't.
In order to remove the spring...
In order to remove the spring from the high-gear/reverse clutch drum, you will need a good spring compressor. The snap ring needs to be removed first. Be very careful while performing this task because the spring is under a lot of pressure. Our high-gear/reverse clutches were burned up. With the entire transmission apart, it's time to assess the damage. Fortunately, we had no "hard part" damage and would only have to perform a "soft part" rebuild.
A torx wrench and screwdriver...
A torx wrench and screwdriver will be needed to disassemble the valvebody. Be careful not to lose any of the check balls.
Our grimy trans case was dumped...
Our grimy trans case was dumped into a sonic cleaning tank. All other parts received a thorough cleaning in the hot tank. Cleanliness is paramount when rebuilding an automatic transmission.