2007 Ram 2500 5.9 Cummins with 48re transmission try's to tow 20,000 lbs. 27,500 lbs gross.

The 48re Transmission... IS the weakest link! LOL Can it tow 20,000 lbs? Yes, but should it? No, It wasn't designed for that. Running a shorter tire or a lower gear ratio like was used on the 3500 dually's you could make do, but at the end of the day the 4 speed auto is not Ideal in heavy towing... The torque converter doesn't lock until 3rd gear which creates extra heat when accelerating through 2nd gear. These trucks were designed to tow 12-14,000 lbs and they do fairly well at that level. Trying to tow 20,000 lbs up an Incline is asking a bit much. This is why the G56 6spd manual transmission option was so popular in these trucks. 48re gear ratios listed below with Allison 1000 used as a comparison reference. Look at the reverse ratio as well, makes a huge difference in backing up a heavy trailer and how much heat is created in the transmission when doing so. 48re gear ratios 1st 2.45/ 2nd 1.45/ 3rd 1.00/ 4th .69 /Reverse 2.21 Allison 1000 1st 3.10/ 2nd 1.81/ 3rd 1.41/ 4th 1.00/ 5th .71/ 6th .61/ Reverse 4.49