Thanks for you reply. I see you have 4. 10's, a 5spd transmission, and a splitter. So I'm guessing that means at 23,000 GCWR that you must be in approx. 4th over? I realize that 2100 - 2250 seem to be ideal towing rpm for the 12 valve, but those rpm's are governed by gearing. At those rpm's in 4th...