I just had a rebuilt 350 turbo put into my car, it seems to shift fine, but it is building up pressure and pushing the fluid out the dipstick tube. What could be causing this?

 

at the bottom or the top of the tube? if its at the bottom,it could be b/c of a bad o-ring seal down there.

 

It may be over filled. It may have a high stall converter that is putting alot of heat in the fluid, causing it to expand and run over. It may have a bad/plugged cooler that is causing the same problem. Or, it may have a plugged vent on the trans case (it is usually on top of the case to vent pressure).

My thoughts.