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When temp. reaches about 135* TCC starts working normally.
Once temp hits 185* or so it stops working.
Initially when it unlocks, lets say at 65 mph, if you let off the pedal and get back on, the TCC locks up for 2 seconds then unlocks again.
After a short time it just doesn't lock at all.
Checked the signal at ALDL "F" terminal from ECU and it seems normal. When TCC stops working the signal is still operating normally.
Does this sound like a TCC solenoid problem or TC problem?
It's a rebuilt unit and I'm not sure the exact year of the trans. It's in an 87 that was converted from a 4+3. Had been working fine for a few months. I know it's a late style case, and it has some sort of temp switch that the wiring runs through on the VB. It had a round plug on it originally, and I had to pull the pan and swap in the square plug.
Like I said, it was fine for a few months and when I first noticed it I would be leave from work in the evening, and about 5 miles down the road going up a grade at about 70 mph and it would unlock, lock, unlock, lock a few times up the grade, and now it's just gone.
The solenoid is easy to check. It shoulkd ohm test at about 20-25 ohms. The pressure switches are either normally open or normally closed. It depends on the year and wiring harness. The switches are checked by removing and pressure testing with 100psi. If they leak fluid or don't close(or open depending on type) it is assumed bad. If any doubt, replace them. $10 each per switch and $25 for a solenoid.