4L80E 1993 6.2 no 1-2 shift

[Blue93cube]

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[Blue93cube]

It never gets that far (3rd / 4th). Is there any test in limp mode to check owc? Would the owc failure still have engine braking in manual low?

 

[Blue93cube]

By never getting that far, I mean I end up getting the RPMs so high up in first because it won’t even try to upshift most of the time that I just back out.

 

[NickTransmissions]

It never gets that far (3rd / 4th). Is there any test in limp mode to check owc? Would the owc failure still have engine braking in manual low?

By never getting that far, I mean I end up getting the RPMs so high up in first because it won’t even try to upshift most of the time that I just back out.

So you never up shift out of first? At all - never? Thought you said that you do upshift, it holds 2nd gear for a few second then falls back to first....here's your post from yesterday:

This is all under light throttle as the 6.2 gets to uncomfortable sounding rpms quickly in first. Shifts into 2nd with no flare or hesitation, holds for a second, just long enough to think it might be ok, then feels like a downshift (revs go up quickly) but no engine braking when I let off the gas like I get rolling around in low. With no tach, I let it slow a bit before getting back into the gas and it’s definitely in first. I’m being extra cautious because I had a bad experience with an auto that decided first was good at 40mph due to bad vss..

So either you have a 'first gear only-no upshift condition' or you do upshift (maybe you just aren't realizing it because nothing is happening mechanically) or you dont. If the PCM is not commanding an upshift then you have a true 1st gear no upshift...If the PCM is commanding an upshift, it shifts - holds for a second or two, then immediately downshifts that's by def a neutral condition in 2nd and the PCM is downshifting you to keep in gear.

Unplug the case connector on the side of the transmission, start it up and see if it goes forward...If it does, then 2nd gear (intermediate clutch pack, forward clutch pack and intermediate sprag OWC) is mechanically capable of proper function. 4L80Es default to 2nd gear only when in limp mode and shifter is in 'Drive'.

 

[Blue93cube]

Almost every lap, it refused to upshift, I would say that if I jumped in it right now ended a lap around the block that would be the behavior. Every once in a while it would upshift the rpm would drop and the van would still accelerate, but then it would rev up, and if I slowed down a little bit, it would be in first gear. I will try to take a short video this weekend.

 

[Blue93cube]

After the TPS swap and adjustment and before the TCM swap, the truck only had second gear and CEL.

 

[NickTransmissions]

Almost every lap, it refused to upshift, I would say that if I jumped in it right now ended a lap around the block that would be the behavior. Every once in a while it would upshift the rpm would drop and the van would still accelerate, but then it would rev up, and if I slowed down a little bit, it would be in first gear. I will try to take a short video this weekend.

Just follow my recommendation above - that will help you determine if you have a command and control problem or a mechanical problem inside the case...If the latter, trans has to come out.

 

[Blue93cube]

10-4, thank you!

 

[Blue93cube]

Just follow my recommendation above - that will help you determine if you have a command and control problem or a mechanical problem inside the case...If the latter, trans has to come out.

Well, possible issue found when unplugging connector, it was full of trans fluid. That being said, unplugging had second gear only and no slipping. Tried cleaning and drying out both sides of connector, no change in behavior.

 

[NickTransmissions]

Well, possible issue found when unplugging connector, it was full of trans fluid. That being said, unplugging had second gear only and no slipping. Tried cleaning and drying out both sides of connector, no change in behavior.

Common issue but at least you know you dont have a mechanical problem in the case that would require overhaul.

Replace the transmission internal harness; many of them leak through the conmector and I never reuse those harnesses when building any trans that uses one...hopefully your external harness that comes from the pcm to the transmission isnt compromised...