86 Camry Overdrive Issue

[toored]

When on the interstate at cruising speed the overdrive intermittently disengages for 1 to 2 seconds as identified by a corresponding rise of 200 to 300 RPM, then back to normal. The overdrive OFF light is not illuminating during the events.Any help would be greatly appreciated!

[fredk]

is the trans full?

[Doctor J]

Can be TC lock-up issue.

[toored]

Yes, the tranny is full of fluid. I apologize, I meant to say that the torque converter is unlocking at cruise speed, not the overdrive - my bad. The overdrive works ok. It has been doing this for a couple of years but is becoming more frequent. Thanks again for any advice.

[Doctor J]

To determine if the problem is electrical or mechanical , you need to attach the indicator light to the lock-up solenoid pigtail ( "back-probe" its connector with unfolded, sharpened paper clip, connect the clip to the small light bulb (12v, 0.04A) with long wire and ground another end of the light bulb). Tape the light to the windshield. When the comp. will command the TC to be applied, the light will be on. If during the RPM jump the light stays ON the problem is mechanical. If the light goes out at the rpm jump, the problem is electrical(could be as primitive as bad connector or Tp sensor/ brake switch input.

This test will not show thw intermitent electrical coil failure of the lock-up solenoid, so if the ellectrical test will be inconclusive you may try to put another good used lock-up solenoid.

[toored]

Thanks Dr. J. I will try the light bulb trick. Where is the lockup solenoid located?

[Doctor J]

Outside of transmission, facing the radiator, next to the neutral safety switch.It is only one solenoid outside of the transmission.