I had my LT1 T56 transmission converted to the LS style T56 for my ls swap. I sent out an extra midplate I had to get converted by alloy specialties and I bought the LS input shaft. Once I received the converted mid plate I took off the one from the T56 but the midplate would not close with the main case. I took the transmission to a transmission shop to have it installed and they also couldn’t figure out why the midplate wouldn’t close. My dad compared both the midplates and noticed that thearea on the converted midplate where the bearing sits was a bit different so he machined it down and the plate finally closed. The transmission shop was the one that installed the midplate after it was machined.

We installed the transmission and bolted everything up to the car but right before I cranked the motor the transmission was leaking transmission fluid from what seems to be between the midplate and main case. Could this be due to a lack of silicone between those two parts or is there something else I need to look into?

Thanks!

 

You may have missed out on proper shaft bearing endplay / preload on assembly.

Yes, and black ultra RTV works fine.

 

Now that you mention the preload, there's a 99% chance the transmission shop did not do this. I do not have the tools to check the preload. I need to call some chops.

Thanks for the tip!

 

Any update?


 

No new updates at the moment. I did reach out to a few other people who have taken apart the fbody T56 and most of them believe the culprit is most likely the shop's low quality work. Either the surfaces were not cleaned enough or they didn't use enough black silicone. When I was trying to find were the leak was coming from I did notice that there wasn't any silicone on the outside of the transmission from when you put the pieces together and the silicone squeezes out. Only one bolt from the mid-plate to the case had silicone on the tip.

One other individual did mention that leak could happen due to not doing the proper preload but without seeing it in person its just guessing.

 

Have your old LT1 mid plate. & if you do are you interested in selling it? Need bad and not rich