I'll take your 10 sp I've a th400. I Ave 30-40k between rebuilds on the two I had. That was with 5-6k fluid changes including TC!
Marty
30-40K on a T-400. You must abuse the devil out of them. Those 5-6K fluid changes were made how often, in months or years? Do you have an aftermarket cooler? Who rebuilds them?
Years ago when I showed horses I had a Chev CC 454/T400 pulling a 4 horse trailer and carrying an 11/12ft camper. I changed tranny fluid every spring and ran an aftermarket cooler. Pull that way for 10 yrs and never needed the trans rebuilt