I have a 2002 F250 7.3L Diesel with 250,000 miles and the original transmission and torque converter. My trailer weighs just about 10,000lbs. It is still going strong but I do change trans fluids and filter every other year. Costs a little over $100 but seems to be paying off.
๐Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine