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4l80e lockup problems

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Old Sep 28, 2011 | 01:13 AM
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BR3W CITY's Avatar
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From: BREW CITY, WI
Default 4l80e lockup problems

I took my 66 on a fairly long trip, and noticed that it didn't always seem to want to lock up the converter at the right times. The truck seems to go through the gears normally, but seems as if it forgets when it needs to take the final step and lock up.

Cruising on the freeway under light throttle, it just doesn't seem to lock up when you'd think it should. All of a sudden under a load like a hill, it then decides to lockup and cruises nicely locked up for a little while. Then randomly it unlocks and the rpms climb up again. I have no clue whats causing this, as lockup DOES work , but just not when it should.

The trans is a late 90's 4l80e, freshly rebuilt and with a 2800 stall (not sure of name, have to find the trans shops sheet). Doesn't leak, seams to run well otherwise. Could this be an internal problem? Solenoid issue? Or is this something that the pcm can affect?
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Old Sep 28, 2011 | 05:45 AM
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From: DFW
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If it locks solidly with no slipping (when it does lock) its likely a tune issue. If you have access hptuners/efilive you can scan it to see if its doing whats commanded.
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Old Sep 28, 2011 | 10:02 PM
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From: BREW CITY, WI
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it feels pretty solid, but it never seems to go into lock long enough to really feel it out. When it goes into lock, it feels pretty much like another gear; if i give it just a bit to bring up my cruising speed, it seems to feel solid..no bouncing or playing catch up like a slipping trans I've had before.

I mentioned it to my tuner and he thought it could be mechanical, possibly something with the converter? He may just be playing CYA tho. The truck was tuned with HPT. Is there a "lockup" command? I haven't worked with hpt myself so not really sure what to look for on that.
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Old Sep 29, 2011 | 11:56 AM
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From: DFW
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Originally Posted by BR3W CITY
it feels pretty solid, but it never seems to go into lock long enough to really feel it out. When it goes into lock, it feels pretty much like another gear; if i give it just a bit to bring up my cruising speed, it seems to feel solid..no bouncing or playing catch up like a slipping trans I've had before.

I mentioned it to my tuner and he thought it could be mechanical, possibly something with the converter? He may just be playing CYA tho. The truck was tuned with HPT. Is there a "lockup" command? I haven't worked with hpt myself so not really sure what to look for on that.
Yes, you can lock it up with the scanner. Most of the time its because the PCM is detecting misfires.
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