1974 Pontiac Trans Am Transmission - Shiftless Pleasure

quick-disconnect fittings at the trans end to mate with Dorman quick-disconnect trans line connectors were installed. All fitting threads had anti-seize compound applied. The Dorman fittings were torqued to 28 ft-lb.

Lokar's Hi-Tech trans dipstick is designed to mount on the firewall. With firewall space at a premium, Scott made a bracket from the firewall to the A/C box and mounted the Lokar bracket and dipstick tube to it, so the trans fluid level can be easily checked.

The GMPP Transmission Control Unit (TCU, PN 12489489) is the heart of the Transmission Control System. This system also includes a wiring harness (PN 12489490), TCU/laptop interface cable (PN 12489579), laptop disc (PN12490207), and specifications (PN 12489491). It was mounted on a bracket that Scott fabricated just under the top of the passenger side fender.

Here is the wiring diagram for the TCU and transmission for reference. The wiring is coded C1 to C12 for ease of installation. C3 provides a computer hook up for the laptop. C4 goes to the distributer to get an rpm reading so the TCU can set WOT shift points. C6 must be wired to a switch on the dash to enable the Performance shift mode. If the wire is not grounded via a switch, the trans will stay in Economy mode according to GMPP. C8 is plugged into C9 and they control the torque converter clutch function. C10 gets taped off, and C11 is optional for a slapstick-style shifter. C12 plugs into the bottom left-hand port of the TCU and is secured with 1/4-inch-head bolt. There is also a black ground wire from the harness to the battery to reduce electrical noise to the TCU, and there's a pink ignition wire that has to be connected through a 10-amp fuse to the fuse box to receive 12 volts only when the ignition is turned to On.

There is also a black ground wire from the harness to the battery to reduce electrical noise to the TCU, and there's a pink ignition wire that has to be connected through a 10-amp fuse to the fuse box to receive 12 volts only when the ignition is turned to On. At the business end of the flexible dipstick tube, the double O-ring seal connector will be pushed into the transmission's port. Then the trans will be filled with approximately 7.7 quarts of Dexron VI fluid (8.25 quarts for us given our cooling system). Fluid level should be checked on the dipstick with the trans in Neutral and the engine running at operating temperature.

Since the SD-455 engine was converted to EFI a few years ago, the wires for the throttle position sensor (TPS) (C2) were simply spliced into the existing EFI wiring harness. The TPS output allows the TCU to determine shift points and firmness.