Towing a 17,000 Lbs 5th Wheel Camper with Ram HD: Does the Rear Axle Ratio Matter? (Ask TFLtruck)

2018 ram hd 3500 camping trailer rv towing
2018 Ram HD 3500 with a 5th wheel camping trailer

We recently got the following question from Lynn. She is upgrading to a Ram HD 3500 dually to tow a big 5th wheel camping trailer. The particular truck configuration she is looking has an optional 3.42 rear axle ration, instead of a 3.73 or a 4.10. The core of the question is: will she be able to tow a trailer that maxes out at 17,000 lbs, and how does the rear axle ratio affect towing?

We are are looking to upgrade to a fifth wheel, and we are looking to upgrade our 2500 turbo diesel to the 3500 turbo diesel dually. We are a bit confused, the Ram HD Laramie window sticker has standard 3.73 gear ratio but under additional options for the vehicle it says 3.42. My question is: can we tow the fifth wheel with ease? The fifth wheels we are looking at has a max weight of 16,000 to 17,000 lbs. The dry weight is evidently less with around 14,000 lbs, and the hitch weight is around 3,000 to 3,300.

First of all, let’s look at the truck you are considering. It’s a 2017 Ram HD 3500 Laramie dually crew cab 4×4 with the 6.7L Cummins I6 turbo diesel, 68RFE 6-speed automatic transmission, and an optional 3.42 rear axle ratio.

2017 Ram HD Towing Specifications

Indeed, the rear axle ratio matters when talking about maximum towing capacity. Why? Here is what Ram says:

 A numerically lower axle ratio results in lower engine rpm and improved efficiency. A numerically higher ratio improves acceleration, climbing grades, carrying loads or pulling a trailer.

The truck you are looking at is rated to tow a maximum of 16,660 lbs, which is not quiet enough if you are planning to tow 17,000 lbs often and over a long distance. I would make sure there is at least a 3.73 rear axle in the truck, or (for an additional $2,600) you could get an AISIN 6-speed transmission and a high-output version of the Cummins for an additional towing capability.

The AISIN transmission is heavier and decreases the payload a bit, but there is still plentiful 5,690 lbs of payload with a dually truck.

Thanks for the question!

Here are the most important things to remember when towing a heavy and luxurious trailer. Check out the video.