age old question. motor too hot.

[zoaman]

hi i run a 4wd indoor on mostly carpet slippy floor.i run a 9.5t 80/26.
this runs in the nice range of temps ,but i also have a spare car with a 8.5t 80/25.
yet the spare car runs way too hot.with the slippy floor area i thought using the slowest takeoff would help with traction so tried running what i thought would be the larger pinion.is 80/25 wrong for a 8.5t?
all drive area is free and not binding and mesh is not tight.
your input is appreciated