727 behind a 5.7 hemi

can someone help me out
My 727 is breaking the stator seals
I thought it was just a fluke so I pulled the trans replaced the rings reassembled
All was good for about 40 miles
Then lost 3rd and reverse again .
Ps
This has never been a problem until I put it in my 5.7 hemi swapped truck not that has anything to do with it