700r4 No Lockup

[Rich84]

I'm having an issue with my 700 not going into lockup.

It will lockup in 4th gear before the tranny gets fully warmed up. Once it gets good and warm, no more lockup.

Any ideas where I should start?

[Just call me Sean]

Lockup is electrically controlled.

[Rascal_one2001]

I would drop the pan and replace the harness and temp switch to make sure everything is hooked up right. Trans should not have lock up until it is up to temp.

[geezer#99]

[QUOTE=Just call me Sean;6848305]Lockup is electrically controlled.

By a switch that is controlled by vacuum from the carb via the thermal vacuum switch on the front of the intake.
Maybe the vac lines are on the wrong ports of the tvs.

[Just call me Sean]

[quote=geezer#99;6848338]

Originally Posted by Just call me Sean

By a switch that is controlled by vacuum from the carb via the thermal vacuum switch on the front of the intake.
Maybe the vac lines are on the wrong ports of the tvs.

Depends. He didn't give a year.

[beamn7]

Originally Posted by Rascal_one2001

I would drop the pan and replace the harness and temp switch to make sure everything is hooked up right. Trans should not have lock up until it is up to temp.

Exactly. Some of these had a temp switch that interrupts the ground signal to the TCC solenoid. Possible bad temp switch or a pressure switch or the TCC solenoid itself has gone bad and has a poor winding that is loosing connection once it is at operating temp.

Wiring configuration, number of pressure switches, temp switch, and if unit has vaccum control lockup or not all depends on year and model....

[Rich84]

I guess I left out some important information.

My truck has a 1985 z28 TPI engine and transmission. I know that the ECM controls lockup when certain parameters are met (speed,Temp Etc..).