To access the wiring that...
To access the wiring that activates the lockup converter, Gene drained the transmission and removed the transmission pan.
Next, Gene removed the transmission...
Next, Gene removed the transmission filter. On TH700-R4 units, the filter is held in place via the suction tube and seal. To remove the filter, simply pull it straight out.
3The original external power...
3The original external power connector for a computer-operated TH700-R4 lockup converter is this four-position connector (right). Since our early-car conversion will use just a 12-volt input, Gene uses a single-blade connector (left) from an early Turbo 400 (GM PN 24205373).
The original connector is...
The original connector is held in the transmission case with plastic tabs.
To remove the plastic connector,...
To remove the plastic connector, push a 3/4-inch socket over the three tabs to release it and pull the connector out from the top.
Reinstall the Turbo 400 connector...
Reinstall the Turbo 400 connector into the same position by pushing down until the three clips latch.
Next remove the multiwire...
Next remove the multiwire harness held in place with three screws and unplug the connectors. There are a few styles of harnesses, so yours may differ slightly.
To operate the lockup converter,...
To operate the lockup converter, Gene uses a normally-open/ pressure-closed switch (GM PN 8627332 or 8642473). Since some TH700-R4s came with a normally-closed/pressure-open switch, Gene always changes the switch to one of the part numbers listed above. Since the lockup function is electronically operated, he also advises adding a secondary ground from the transmission to the body or frame.
Gene used a medium pair of...
Gene used a medium pair of channel locks to remove and install the switch. Gene recommends using pliers to avoid tearing the gasket when removing the accumulator.
If the accumulator is removed,...
If the accumulator is removed, the switch can be removed and installed with an oil-pressure-switch socket.
Some valvebodies use many...
Some valvebodies use many other switches not required by noncomputer cars. You can leave them in place or plug them with 1/8-inch pipe plugs.
If your converter clutch lockup...
If your converter clutch lockup solenoid only has one wire (left), it must be replaced with a two-wire style (right). Note that the one-wire style is self-grounding and will lockup the converter from Second gear and above without a computer.
Two-wire converter clutch...
Two-wire converter clutch lockup solenoids will have the wire color stamped in the bracket adjacent to the wire.
Cut the connector that went...
Cut the connector that went to the oil-pressure switch from the original harness and splice it to the black wire from the converter clutch lockup solenoid. Then cut the red wire from the converter clutch lockup solenoid and route a length with a connector to the new Turbo 400 switch.
Make a new harness with the...
Make a new harness with the black wire (A) from the converter clutch lockup solenoid to the oil-pressure switch and the red wire (B) to the Turbo 400 single-blade switch. To activate the converter, run a switched 12-volt source to the single-blade connector outside the transmission. Ask Auto-Rite about its ready-made conversion kit (PN AR-700-L/V).
Remember when installing the...
Remember when installing the filter to remove the old O-ring. Be sure the new filter is fitted with an O-ring. With the new filter installed, replace the pan and add fluid. Be careful not to overfill the transmission.
To any hot rodder, a hard-running small-block with deep rearend gears blasting through the quarter-mile at over 7,000 rpm sounds great. But driving that same hot cruiser down the freeway at anything over 3,000 rpm gets old fast. To be able to blast low e.t.'s and effortlessly cruise the freeway, many hot rodders have discovered the benefits of overdrive automatics. But because electronic-overdrive transmissions are designed for computer-age vehicles, the dilemma becomes how to activate a lockup converter in a noncomputer musclecar.
The good news is that with a few hours of work and some know-how, that late-model automatic with its lockup converter can put your vehicle's performance into overdrive.
Recently, we spent the morning with Gene Christensen from Auto-Rite Trans-missions to learn just what is involved in wiring a TH700-R4's lockup converter into a noncomputer car. What we're doing here is using a Hobbs pressure switch to complete an electrical circuit that activates a solenoid in the transmission to apply the torque converter lockup when the transmission shifts into overdrive. To be able to demonstrate the steps easily, we used a transmission on a bench, but the procedure can be done with the transmission in the vehicle. Here's what we found.