Any 3.42 Axle Ratio Experience
 

I am close to pulling the trigger on an order. Has anyone on the forum taken delivery of a 2500 with the Cummins, auto, and 3.42 gears? If so, any comments? I know the 3.42 gears are not popular on this forum as most of you probably use these trucks for what they are intended for --- big loads. I will be towing light (less than 6K) and most use will be virtually unloaded. The Dodge engineers via phone call and a very experienced Dodge mechanic who is the "Cummins expert" at a local dealership advise the 3.42 gears if I order the truck. I did find a truck in Idaho (where I will be going next week anyway) that has a Laramie configured the way I want but with 3.73 gears which would likely work OK for me -- but the 3.42 gears should result in some optimum interstate cruising mileage in my opinion. Seems to be a good use of the exceptional 1500 rpm torque in the Cummins. Ed

At 6000 pounds it will work hard off the line pulling your loaded trailer. But if it is not dealing with much mountain terrain and only on occasion it won't hurt much. You will be very happy in the mileage dept. though. I see the truck empty on highway near 30 mpg's. I have 4:10's and do around 25 at 50 mph and 21-23 at 60 mph with the 5.9L.

I don't know how well the 6.7L is doing in MPG's.

I had a 99 1500 burb T/D w/ 3:42's and it worked had off the starting line pulling a open loaded car trailer but once it was moving it was fine.

Where about in Idaho? I've dealt with a few of the dealers in the Boise area, and Dave Smith up north in Cd'A.



Kris

Dave Smith was the dealer in Idaho I spoke to -- big big dealer. But they didn't have a Laramie like I wanted with 3.42 gears -- 3.73 gives better tow ratings and meets more peoples requirements I assume. Some dealers I talked to didn't even know what I was talking about, I guess the 3.42 option is new for 2010 (so I assume some customers indicated they wanted higher gears).

Just my opinion. You said most of time empty. I would get the 3.42, you will be much happier without the unnecessary RPM's on interstate. BUT, I have a stick, so have no experience with auto.

From the couple 6.7/68rfe trucks I've driven, even the 3.73's have real nice cruising rpms. Wanna say less than 2k rpms at 70 mph. I'd love 3.42s in my 07 G56 truck and would drive a ways to swap with anyone who thought their 3.42s were too tall.
For my driving, if given the choice on a new auto trans truck, I'd take 3.73s, but wouldn't pass up 3.42s for the same $.

With my '06, 5.9 48rfe I would cruise at 70 mph and right around 2,000 RPM.
With the '10, 6.7 68rfe, 70 MPH is around 1700 RPM.
The 3.73 rear axle was/is in both.

I think with the 6spd auto you'd be happy with 3.73. If you even think about taller tires in the future you'll wish you had 3.73's.

OK - Here is a table I just came up with, using the tire revs/mile directly from the BFG spec table and what I was told the 6th OD ratio was in the automatic:

Trans Tire size Revs/mile MPH axle ratio OD ratio 6th RPM

Manual 265/70-17 654 70 3.73 0.74 2106
Manual 265/70-17 654 70 3.42 0.74 1931
Manual 265/70-17 654 70 4.11 0.74 2321

Auto 265/70-17 654 70 3.73 0.63 1793
Auto 265/70-17 654 70 3.42 0.63 1644
Auto 265/70-17 654 70 4.11 0.63 1976

Based on this, I can see why the 3.42 would not be so good with the auto, and the 4.11 not so good with the stick. I'm surprised by the higher OD in the auto, and having just ordered a stick, I'm wondering if I really should have stayed with the 3.42 gears, assuming most of the heavy hauling would/could be done in the 1x1 5th gear.

The difference between the 3 rear ratios is consistently about 9% by the way. Changing up to a 285/70 tire drops the revs by about 3%

-truckin-on

If I didn't want a bigger Travel Trailer in 2002 I would have never traded in my 99Burb 1500 T/D. It got good mileage with the 3:42's. I reckon that 1644 rpm at 70 mph will equal some great mileage. Even better at 60. I have 4:11's which I would not have ordered if I had bought the truck new. This thing tears the road a new one and stops at nothing especially while pushing snow but more mpg's would be a sight for sore eyes. If Gear Venders were not so expensive I would install it for the highway runs.:(

I didnt think you could get the auto with 3.42's. I thought it was only an option for the sticks. I would not get an auto with the 3.42's anyways. Any slower than 70 and that truck would be useless in double overdrive. IF you ever plan on running 35" tires on your rig, get the 4.10's. The 35's essentially change your ratio from the 4.10's to the 3.73's. Buddy put on 35's on his 09 and his rpms are very low with his 3.73's. He wishes he got 4.10's and he tows maybe three times a year.