4r100 locking and unlocking converter repeatedly

PSD_ · Aug 21, 2015

Have a bts with pi converter and under normal driving today it started locking and unlocking the converter. I talked to Brian and changed the TPS and the gear selector switch on side the trans also changed alternator.

I've read about the 3rd brake light causing this issue but mine is working right.

I don't know what else to change it is not giving and trouble codes and the O/D light isn't flashing

Still at 40-45mph it's locking and unlocking like crazy no slipping or any other problems

mandkole · Aug 21, 2015

Sorry, its happened to you too.. Unless its throwing electrical codes for a bad circuit or bad solenoid pack, the TCC is likely slipping-- just went through this, spent a lot of time studying it, and have couple of threads on it. Mine had been slipping for awhile before it started to act that way. Others with BTS/PI combos have had similar issues.

The converter locks, then as soon as you apply a little load, it senses excessive speed differential between input and output (slippage), then it unlocks. Once unlocked, it wants to relock. Temps also take off if exposed to load.

I dont know what to say about the PI converter, except that it was some bastard collection of components and thrown in the trash. the BTS had the 2nd and 3rd direct clutches were hammered.

PSD_ · Aug 22, 2015

That's what I thought from the get go. Called PI and they swear it can't be the converter. They claimed it was something tellin it to lock

mandkole · Aug 22, 2015

The PCM is telling it to lock and unlock because of the speed differential its sensing. I ran the AE and you could watch the slip increase until it unlocked. Once it was unlocked, it quickly realized it shouldn't be unlocked and locked again.

In my case the converter had been drifting on due to a pressure leak or other issue affecting the TCC apply. It was slowly killing itself until the lining on one disk of the TC clutch was gone.

some reading that may help..
http://www.sonnax.com/articles/198-4R100-Repeated-Converter-Failure

Just replacing the converter may not fix it and you should look at the pump and the transmission. Not sure how many miles on it, but you may want to take it back to Brian.