I just got my t56 back from the tranny shop yesterday and installed it but when i was driving it later on that night the output shaft seal popped out. I put it back in and drove around all day today and started cruising on the highway and it popped out again, this time almost all the way out. Anybody have any idea why it would keep popping out?

 

Is the rear housing where the seal rides messed up?

 

Either the wrong seal was used, or
the multi-lip externally ribbed Tremec seal is loose (see https://ls1tech.com/forums/manual-tr...rs-beware.html ) and you should get a Timken 9613S (included in the #5200 bushing/seal kit) or equivalent instead, or
the steel frame of the seal is bent, or
the tailhousing seal mounting location i.d. surface is damaged.

The slip yoke should have nearly no up/down play allowed and shouldn't be part of the equation due to vibration or movement.

If you were able to pop the seal in fairly easily, a new seal would be recommended, assuming no damage to the tailhousing.

 

If they used RTV around the seal, it will usually pop out. It has to be installed dry. I never really liked the rubber seals. I'd recommend using a TH350 rear seal (flat, metal, orange in color). They're only a few bucks and work great. We use them in all T56 builds and never a problem.

 

Same seal we use. I've never had an issue with them either unless they were installed incorrectly.

 

The guy installed the seal dry and the tail housing feels fine and has no cracks or anything. I went back to tranny shop today and they guy gave me a different seal (th350 seal) and told me to try it. Thanks for all the feedback and advise.