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4T65E-HD Torque Converter Random Unlock


Addicted To Boost
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On my 06 GTP for about the first 20 minutes of driving, the torque converter will randomly unlock. There seems to be no rhyme or reason to it, it is really random and it will do it on completely flat ground with the cruise set at 70. Other than that, the transmission feels great... very smooth through all gears and no slippage. It will do it in 3rd gear with the torque converter locked and also in 4th locked. What's really odd is that it stops doing it after about 20 minutes of driving on the highway. What could be causing this? Fluid level is good.

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well, what i would do is be watching TCC status and TCC PWM duty cycle when the unlock event happens. no significant change from the PCM = trans issue. significant change = PCM/sensor issue.

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I dropped the trans pan last night, replaced the filter and cleaned the pan and magnet. Fluid looked really old, but not burnt... nothing abnormal found in the pan or fluid, but about 1/8" of sludge on the magnet. Buttoned it back up, pulled the tranny cooler feed line and put a bucket under the car and poured in new fluid until it came out a nice bright red, took 15 quarts all together.

 

Drove it to work today and the torque converter is now acting normally. No more random unlocking and engagement is much more smooth. I'm going to have it tuned on Friday as well- change the shift times to 0 for no clutch slippage, increase my line pressures across the boards and get rid of the dumb floating lockup program GM has for the torque converter below 55 mph. Removed that from the Comp G and it made a world of a difference.

Edited by Addicted To Boost
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dumb floating lockup program GM has for the torque converter below 55 mph.

 

 

So, that's what that is. The Aurora had that bad and always pissed me off. I always wondered of it was a tune thing or just the slushbox PS acting up.

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So, that's what that is. The Aurora had that bad and always pissed me off. I always wondered of it was a tune thing or just the slushbox PS acting up.

Yes, it's very annoying. I don't know wtf GM was thinking when they had that programmed in. Basically your torque converter is programmed to only be locked between like 25-35% throttle and anything above or below that makes it unlock. I had that removed from my comp g and it helped a lot. That floaty unlock program causes a lot of unnecessary wear on these transmissions.

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Glad to see you got this issue taken care of. :thumbsup: I used the same fluid in my trans for a couple spill and fills and it seems great so far.

 

I must say, I'm very interested in this torque converter programming and changing the shift times to 0. My 4t60-e does the samething and I would love to fix it. I may have to ask Camron to get out HP Tuners sometime and give me a hand. Not sure if you can change those settings on my PCM, but a man can hope. :lol:

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changing shift times to 0 won't do anything for a 4T60E... PCM doesn't control shift feel(vacuum modulator in combination with the accumulators does).

 

as far as stupid GM transmission programming, yes..... it's pretty bad at times. especially in ~98 and up cars, where they have the ECCC system where the TCC is designed to be slipping at all times. heats the hell out of the fluid and generally just feels bad.

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