Allison 5 speed/Duramax

k7nnv · November 13, 2001

I have ordered a 2002 2500 HD 4 WD LS Extcab long bed w/ Duramax and Allison 5 spd transmission. I have read on other forums about a problem with the transmission down shifting from 5th gear on mild grades while towing and keeping the engine at 3000 RPM and resulting in lousy fuel mileage. Any one out there had similar problems?

Derek M · November 13, 2001

I towed my car and trailer to the track just over a week ago and never once got it to downshift out of 5th even while using the cruise contol. The Allison peformed perfect.

02_2500hd · November 13, 2001

I haven't been out on the super highways with a trailer yet, but I have been around town and a few back road with about a 10,000lb load and the Dmax and Allison worked great. I only put it in tow mode to start and stop.

I have run about 1000lbs in the bed on several long trips up and down some 6% grades, and going up the hills, the CC set to 70 and it hardly every waivered and no noticeable different sounds coming from the engine. If I hadn't been looking out the window, I would have said we were on a flat highway.

It was wonderful.