My 2021 2500 Cummins blew the trans while towing 10k trailer in mountains. Coming back from weekend and doing the 3 mile climb from hwy to house when near driveway hear loud bang and the smoke everywhere. Was able to get into driveway, but stuck with 5th wheel attached. No forward gears only reverse and trans dip stick blew out spraying trans fluid everywhere. The road to house is only 25 mph so not racing it . Very disappointing to say the least, not sure if bad trans or this truck can’t handle towing at 9,500ft elevation . Hopefully dealer will give me loaner while in for repairs. Maybe time to jump ship to 3500? Looked at 2022 and still no Allison trans, come on 6spd is yesterday’s technology.