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
blt2ski wrote:
Roy
I believe you are correct for class 8s. I have not looked into the heavier setups in awhile to see how they are doing things.
I do generally speaking like my direct drive Spicer 7 SP in Navistar. I do wish I had an OD, or 3.42 gears and a lower yet 1st than the 10.08 I have. That so when empty, I can cut rpm's down to 1809-2000 vs the 2400 or so I go at 60. But with a 175/385 non turbo diesel, I need to turn a high amount of R's to motor at 60 at any major gvwr above 18-20k even on a level.
I would agree, unless one take trans, and tire diameter into the equation, rpm peak torque, HP needed, actual best axel ratio is a **** shoot!
Marty
Most of the tractors at work have 13-15L engines, 3.50 gears, and OD in high gear-65MPH is 1400RPM. Three have Cummins L9s, double-OD Allisons with 5.38(!) gears...and the transmissions start in second gear. They are geared WAY too low (1900RPM at 65), and would be much better with 4.56 gears.
