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Call or Text (352) 722-5295Differential fluid for the 2010-2018 RAM 6.7L Cummins
A 4x4 6.7L Cummins Ram has two differentials to service: the AAM 9.25 front axle and the rear, which is an AAM 11.5 on most of these pickups and the larger 11.8 on some later 3500s. A 2WD truck has only the rear.
Why the fluid matters
Gear oil is the one part of the axle you replace on a schedule. Among owner reports for these trucks is a 2015 3500 whose differential seized after an oil change, with a howl before it locked up. That is a single report, but it is reason enough to use the right fluid and fill it correctly every time the axle is opened. If you are installing a finned aluminum cover at the same time, buy extra; those covers add fluid capacity and cooling.
Picking a grade
The grade in this collection that matches the factory viscosity is 75W-90, offered here as Lucas Oil Synthetic and in both Hot Shot's Secret lines. The grid also carries 80W-90, 80W-110, 75W-140 and 85W-140 for owners who choose a different viscosity. Before you buy, read the product page for the rating and compare it with the GL-5 synthetic spec.
What we carry
- Lucas Oil Synthetic 75W-90 and 75W-140, plus Heavy Duty 80W-90 and 85W-140.
- Hot Shot's Secret Blue Diamond HD Synthetic and ADRENALINE Synthetic Racing gear oil, each in 75W-90, 80W-110 and 85W-140.
- Royal Purple Max-Gear 75W-140 synthetic.
- A BD Diesel 14-bolt AAM 9.25 front differential cover for earlier trucks in this range.
Fitment notes
The fluid spec holds across this generation, but the interval changes: 2018 trucks run 20,000 miles between severe-service changes, earlier trucks 15,000. The BD Diesel front cover listed here is the 14-bolt version, listed through 2012 on the 3500 and 2013 on the 2500; later trucks take a 12-bolt cover.
Frequently asked questions
What gear oil does a 2010-2018 Ram 2500 or 3500 with the 6.7L Cummins use?
SAE 75W-90 or 75W-85 GL-5 synthetic. The 75W-90 synthetics here match that viscosity; confirm the GL rating on the product page before you order.
How often should I change the differential fluid?
On the severe-service schedule it is every 15,000 miles or 12 months on 2010-2017 trucks and every 20,000 miles on 2018 trucks. On a 4x4, doing front and rear at the same visit keeps both axles on one schedule.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.