Re: Chey 700/R4 on a Straight 8

Posted by BH On 2010/7/31 19:47:40

I may be able to shed a little light on the torque converter clutch (TCC)

Although the TCC in the 700R4 is controlled by the ECM in factory installations, getting the TCC to work without an ECM is nothing new. While there are aftermarket kits to accomplish this, many rodders using this trans in other cars have been doing it for years, from scratch.

The "signal" to engage the TCC actually originates with the 700R4 transmission, via a pressure switch, which makes or breaks a connection to ground; some have N.O., others have N.C. contacts. The ECM merely acts as a switch for the TCC solenoid, but likely incorporate other inputs in deciding when the TCC should be engaged.

You can use that pressure switch to control a relay, which is used to energize the TCC solenoid and engage the TCC. However, I believe that you would also have to wire up a brake pedal switch to the relay control circuit to disengage the TCC when braking.

Mind you, I've never done this myself with any 700R4 in any car - merely theorizing. You will need to exercise your own due diligence.

However, aside from the cost of installation/adaptation, I think you'll find it more costly to overhaul a 700R4 than any Ultramatic. Sooner or later EVERY automatic requires an overhaul.