I am still looking to find out if anyone knows if the TCM is programmable. I taking delivery of my new 05 3500 crew cab DMAX and want slightly larger tires. The tranny is supposed to have trouble shifting under a heavy load with anything from 285 and up.I will be towing around 9500-10,000 so do not want any problems. Thanks for any help.

The larger tires mess with the shift points of the transmission. You'd be alright with a 265 but anything bigger then that with a heavy load will affect how it shifts.

I also seem to remember the dealerships will not diagnose any shifting concerns if the tires are not stock.

hey thanks that is what I figured at least 265's are an option from the dealer.