torque converter

[Mr. Don]

My torque converter won't lock up on my 95 yukon 5.7 460le. We ran the diagnostics and it showed nothing wrong, it shifts as good as ever, just won't lock up. We changed fluid & filter to no avail. Thought it might be the ECM, so we changed it out, still no change. What do we check next? According to the diagnostics list it would show if the solenoid or converter were bad.

[redvett]

I would check the brake switch first. PCM sends signal through the switch to trans.

[Mr. Don]

Thanks Redvett, we checked the switch, I wish that was it.

[redvett]

I would suggest you put truck up on hoist or jackstands with vehicle hot and run in drive and check at the switch first for TCC enable. If there is a signal then its in the trans. I could be the solenoid or wireing. If you have access to Tech 2 or simliar scanner you can drive the vehicle and observe TCC on the scanner.