1974 Trans Am SuperMatic Transmission - Shiftless Pleasure

With a quart of Dexron VI in the torque converter (to prime it) and the unit mounted on the input shaft and properly seated, the SuperMatic is ready to be lifted into the Trans Am. Note the output shaft has 32 splines, just like the Turbo 400, which means the yoke on the driveshaft will not have to be changed.

The Turbo 400 mount (left) uses two bolts to mount to the transmission that are spaced 41/4 inches apart. Conversely, the 4L85-E SuperMatic trans mount also uses two bolts to secure it to the transmission, but they are only 33/4 inches apart. So the mount will have to be changed to the 4L85-E type. Also note that the 4L85-E mount uses only one stud and a nut to attach it to the crossmember and the Turbo 400 mount traditionally uses two bolts to attach to the stock crossmember.

Also, since the location of the trans mount is further back on the SuperMatic than it is on the Turbo 400, the crossmember had to be modified or replaced. Scott cut the stock piece to help with measurements ,and then decided it was easier for him to simply make a new crossmember from stock mild steel. Classic Restorations will make one for your swap for $375, or you can modify your existing crossmember to move the mount back.

Since the transmission is longer, the driveshaft had to be shortened about 35/8-inches (and rebalanced) to ensure a proper fit.

With the SuperMatic bolted into the adapter at the bellhousing (bolts torqued to 37 ft-lb) and secured at the crossmember, the torque-converter lugs were lined up with the flexplate bolt holes, 15mm-headed bolts (with blue Loctite on the threads), and the supplied spacers (to compensate for the 5/16-inch thickness of the adapter) and were installed and torqued to 60 ft-lb in two passes.

The stock speedo cable was screwed onto the tailhousing.

Note the new laser-cut and hardened detent already in the shifter mechanism (the stock rivets have been drilled out to remove the old detent and the new one was installed with screws and nuts) and the new lens indicator next to it (on top of the author's flash case), which are part of the Shiftworks Shifter Conversion Kit (PN SC2262). Additional hardware and brackets are included, and the original shift cable can be retained.

Here's what the shifter will look like after the upgrade. Note the new OD position.

Here is the control-cable retaining clip being installed. Also included in the Shiftworks Shifter Conversion Kit are the shift lever and control cable bracket, shown. The secret to fit four gears into a three-speed shifter is the correct ratio of movement of the shifter cable at the trans-mounted shift lever per gear change at the new shifter detent. To do this, the distance between the cable pin and the cable bracket has to be adjusted using the lever's slot to 57/8 inches apart before the pin nut is tightened (with the shifter installed, in the OD position, and the shift lever on the trans in the same position). With the mechanical areas of the swap mostly complete, next month we'll dive into the electronic and cooling aspects.