The 3.43 Rear end

Cummins12V98 wrote:

Wiley75 wrote:

AlaskanHillBilly wrote:
I have a 07 Dodge and have a 3.73 rear end. I am thinking of trading it for a 2013/14 and have been told that I would get better gas mileage with the 3.43 rear end. I am towing a 14,000 lb 5th wheel. Does anyone know if that is true.

Hey there. I did a bit of research on this topic as well. Here is my opinion:

Given that the torque curve of the new 850 ft-lb Cummins is not flat anymore, and that it peaks out at 1700 rpm rather than 1500 rpm like previous engines, it seems strange to me to have a 3.42 axle ratio. On the other hand, having 4.10 axle ratio, putting the engine way above peak torque, would not be wise either. With the new Cummins/Aisin combination 3.73 would be the best match by far in my opinion. For 2013 you can only get 3.73s in a dually, not sure about 2014s though. (I should note that IF my truck was going to be a daily driver/commuter and would only pull hard a few times a year I might try 3.42s anyway, even if they weren't the best combo for towing)

Peak torque of 850 Cummins = 1700 rpm
RPM at 70mph with 3.73 = 1750 rpm
RPM at 70mph with 3.42 = 1590 rpm

All single rear wheeled 2500 and 3500 2013 Ram trucks have 3:42 ONLY.

All 3500 Ram Dually's are available in 4:10, 3:73 and 3:42.

I am pretty sure this is correct so please correct me if I am wrong.

You're right. One difference also between SRW and DRW 2013 3500's is that the RAWR for the dually is 9750#, for the SRW it's 7,000#, no biggie, but yet a difference... I opted for the 4:10, though believe from all I've read the 3:42 as well as the 3:73 gearing would have sufficed...seeing as how a lot of my towing is on some very curvy mountainous secondary roads, 'tis the reason I went with the 4:10....but as has been stated, believe any would work well unless towing a 5er in the +20,000# range, (22-25,000#)...then, 4:10 I would think would be best.