Step one is to have the transmission flushed and replaced with pure synthetic fluid. Sine the rental companies never seem to bother explaining the Tow Haul function {I make it a point to chat with renters and not once have met one who'd even heard of TH}, very few renters ever use it. This results in the not so slow cooking of the trans. Replacing the differential with synthetic is also a good idea along with switching your oil.
While rentals receive regular maintenance they also receive a lot of severe abuse. Every Class C that has ever blown by me doing g 75 or 80 was a rental but fortunately most are V-10's that are relatively bulletproof. With rentals you pays your money and takes your chances but frankly I wouldn't.
As always.... opinions and YMMV.
:C
