The 3.43 Rear end

Brewurown wrote:
I too have a 07 2500 Dodge with a 3.73 ratio pull a 14000 lb 5er. I average 13 mpg. I looked at the new Dodge 3500 DRW and most of them had the 3.43 rear end. 3.73 and 4.10 is available. I think 3.43 might do better mpg not pulling but not as good pulling. Maybe someone with a new Dodge has has some info.

My 2004 Ram Cummins with the 3.73 rear and 6 speed manual, pulling a Keystone Laredo 27RL averaged about 14.8 mpg.

My new 2013 Ram Cummins 2500 with the 6 speed auto, towing the same trailer and along the same route gets me almost exactly the same fuel mileage. The truck only has 2,000 miles on it, and I'm told the fuel mileage will improve a bit after it gets a few miles on it.

On the 2500, the 3.42 rear end is the only one offered. I, too, questioned the suitability of this ratio for towing, but, after a trip thru mountainous country, I'm convinced all is well. That truck is a towing monster. I do realize that my fiver is not as heavy as many on here have.

This was mentioned in another thread, RE a potential owners concern in rear axle ratios 3:42 v 3:73 v 4:10.

The 3:42 ratio from Ram is rated to pull up to a 20,000 pound trailer.

And, as mentioned in the other thread, if the RPM'S are a little low in sixth gear, using tow/haul feature pull it in fifth gear and one should hit that 1700 RPM sweet spot just fine.

Does the Aisin have two OD gears like the Dodge in-house tranny. I think you need look at gear ratios.

Answer is yes. 5th is .77 and 6th is .63! I would want the 3.73 for sure or maybe the 4.10's if towing heavy most of the time. Chris

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.

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

I think given the difference in model years it's going to be more dependent on the engine.

I too have a 07 2500 Dodge with a 3.73 ratio pull a 14000 lb 5er. I average 13 mpg. I looked at the new Dodge 3500 DRW and most of them had the 3.43 rear end. 3.73 and 4.10 is available. I think 3.43 might do better mpg not pulling but not as good pulling. Maybe someone with a new Dodge has has some info.

Probably slightly better mileage non-towing and empty.
3.73 is a very good all purpose rear end...especially coupled with a 6 speed tranny.