Cummins12V98 wrote:
"I know you've had good luck with your previous 2011 3500, and I factored that into my decision as well."
YES I did have good luck with my 68rfe towing 28-29K combine for over half of the 65K I owned it. I removed the MagHytec double deep trans pan just before trading, this is what it looked like with at least 50K on the AMZ/OIL Universal ATF.
I pulled the drain plug then removed the pan, I did NOT pour out the fluid.
I would HIGHLY recommend AMZ/OIL SevereGear 75-90 front axle and same for rear towing occasionally but towing heavy or a lot use 75-110. Get rid of the OE lube within 5K as it is NOT a quality GL.
That's a shame you have to do all this to keep your transmission happy.