Dave,
The torque converter lockup clutch will not release as long as you leave the switch in the lockup position irreguardless of throttle position. It is manually locked and will not release automatically. You have to return the switch to the automatic position to release the lockup clutch solenoid. As long as the TC is in lockup it will not shift down either. If you try to come to a stop with the lockup switch in the lockup position, it will kill the engine. The truck will shudder like a gear drive if you forget to push the clutch in.
If your 96 is like the 97s, you must also remove the relay in the PCM and put in a jumper wire to the torque converter lockup solenoid. Ohtherwise you get feedback and ECM doesn't know what to do.
Bill
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97 3500CC,Auto,4. 10LSD,All Options incl Leather,Pyro,Boost,Trans. Temp Gauges, PacBrake, 3 pos TC Lockup Switch, RPM 40Gal. Aux. Fuel Tank, Reese 20K Hitch, Highway Products Tool Box, 80% Towing 12,100lb. HitchhikerII 5'er. 2000 3500QC 6 Speed,4. 10LSD,SLT+ on Order since 9-28-99, Built 12-01-99, Sitting in Rail Yard Waiting on a Train--Letting the Paint Dry!!
[This message has been edited by Bill Stockard (edited 12-04-1999). ]