3.31 gears at 40,000 lbs gross.
Just to give a bit of a feel for how different gear ratios would behave while towing I locked out 10 then 10th and 9th then added them back again while travelling on a straight stretch of road w...
Forum Discussion
larry barnhart wrote:
When we tow up a mountain our truck wants to keep pulling but I feel better going to 4th gear and let the engine run more RPM's. not the same truck as the posts are telling about but have not had any driveline issues on any towing truck we have had. chevman
GM gives you the ability to lock out 5th gear for the reason you are using it. However, I always felt the computer did a pretty good job of selecting the appropriate gear pulling grades with my Duramax. Going down hill was a little different. In order to get any degree of engine braking with my ‘03 Duramax I needed to be in 1st gear listening to the engine rev to 5000 rpm.
In case you’re interested 5th gear with your Duramax /Allison falls between my 7th and 8th gear in my Ford with a 3.31 rear axle and your 4th is about equivalent to my 6th.
