I need a little help . . . I recently had a local guy rebuild my 4L80e after completely killing the 2nd gear clutches. It would still hold under light load, but if it was given any mild to hard throttle, it would slip.

Before I killed 2nd gear, every once in a while, the truck would free spin, or slip when given throttle from a dead stop, or from a slow roll from a stop sign.

Now after the rebuild . . .

Trans was rebuilt with Raybestos clutches, steels, new wave plate, TransGo HD2 kit, and a new forward drum. Everything else looked spotless. I also added a smaller than stock multi-disk Circle D 3,000 converter. (kinda loose, not the best for towing)

After the rebuild I now have a low RPM vibration when the converter is locked up. If I'm in 4th, and locked up, going 80mph or more, it's very smooth . . . no issues.

If I'm locked in 4th from 62-75 . . . there's a very noticeable vibration, pretty much shakes the truck when there's a blow out.

If I'm locked in 3rd gear, it does vibrate some, but nothing near as bad as it does in 4th. . . .

Do I need to do the TransGo 48-ACT-TL kit ? . . . truck had 140K miles on it when it was rebuilt.

 

Try locking it up in 3rd, but at a slower speed (where the rpms match your 62-75 vibration in 4th). It sounds like maybe an out of balance converter.

 

It does it in both gears around the same RPM

 

Does it do it unlocked at that RPM? Try it in neutral to see what happens....

Chris

 

no issues in neutral . . . . I'm pretty sure that if it was not balanced correctly, that it would get worse with the higher RPMs

 

I've seen an untrue input shaft cause similar issues.

 

Its got a huge a$$ transfercase attached to it

 

Do you notice the vibration any in 1st and 2nd at that RPM. And what is the RPM it vibrates at?

 

Man . . . working late Chris ?

I've only locked up the converter in 3 and 4th . . .


Guess I can try commanding it with the diag tool in the log

RPMs are around 2100 - 2,600 ish . . .

I'll try it again tomorrow morning

 

I meant unlocked in 1st and 2nd. Try to see if it there....

Chris