Rnpeder:
I ran a #6 TST for 50,000 miles with NO PROBLEMS
anywhere and I was pulling my 18 foot racing trailer
in the mountains on I-77 with 4-5% grades.
This was with the stock torque converter and valve
body, however, I did have a "Trans-Go" Shift Kit
in there.
At 98,000 miles I finally "upgraded" the transmission.
Hope this has helped you.
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John_P