My 4L80E lost second tonight on a WOT 1-2 shift. It slammed like it always does on the 1-2 shift, then released and hit the rev limiter. 1, 3, and 4 work fine. Lockup works fine. 2nd doesn't work in any gear position, including manual hold 2nd. Trans is vacuum modulated, and has the full manual 1-2 valve body by TransTec.

Any ideas?

 

dont have any idea but i bet your gonna have to pull it..have fun..trans problems suck..

 

Sorry to hear that. How many miles are on it? By full manual valve body you mean you need to physically shift it yourself?

 

Intermediate Sprag gets my vote. It's between the direct clutch housing and the center support.



Tone down those shifts, slamming clutches is bad.

 

It's vacuum modulated, I can't adjust the shift pressures. My builder set them and I haven't touched them.

By full manual 1-2 I mean that if I put the selector in 1 or 2, it goes not matter what. Even if I'm doing 120mph....put the selector in 1 and you're going for a wild ride

 

James,
If you have large holes drilled in the separator plate and an otherwise agressively set up transmission, can you accomplish this with your commanded line pressure in the tune?

 

For a transmission where the PCM is still in command of line pressure, sure... but only to a point. You would not want line pressure to have to be so low that other already-engaged clutches have a hard time holding.
A vaccuum-modulated unit can be modified by restricting the feed hold in the separator plate. (Not easy) I've hit one with a MIG at very low power to accomplish this, but any spatter sticking to the plate in other areas can cause gasket blowout and trans failure. Plate warps easily too.
A higher-stalling torque converter softens shifts too.

 

I was with him when it happened. By loosing 2nd, what he is referring to is that it shifts like there is no second, stays in first till it's going fast enough to shift in to third, even if you manually put it in to second, just stays in first. When it does finally shift from 1st to 3rd, it shifts really hard. Right Chris?

 

Chris sorry to hear that you are having trans problems.

 

Oh great another broken 4l80e thread

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