rear axle gear ratio
Getting ready to move up to a 3500. I've shopped the available trucks, and have a good idea of what I want. The two I have narrowed down to are a '14 and a '15 Ram 3500. Identical with the exception o...
Forum Discussion
tinner12002 wrote:Kevin Todd wrote:
Thanks for the replies. I'm surprised at the one reply stating less than 1 mpg difference.
I'm not, I'm betting there wouldn't be anymore than that amount of difference in real world driving! I've driven both under the same conditions and there wasn't hardly a noticeable difference in mileage but the 4.10s sure roll off a lot easier.
It is interesting to do the math on the overall ratio in 1st gear on different trucks with different transmissions and rear ends. For instance the 68RFE transmission offered on the Ram has a 1st gear ratio of 3.23:1. So if it has a 4.30 rear axle the final overall ratio in 1st gear is 4.3 x 3.23 or 13.89. The Aisin has a 1st gear ratio of 3.75 so an Aisin with 3.73 gears would have an overall low gear ratio of 13.99. Then consider the extra engine torque available with the Aisin transmission. 13.99 x 900 lbft = 12600 lb ft of torque. Compare that to a 2006 Ram with a 4.10 rear end and 2.45 first gear ratio and 610 lb ft engine - 6127 lbft of rear axle torque. So the Cummins/Aisin with a 3.73 rear end can put over double the toeque to its rear axle as the '06 Ram with 4.10 gears.
