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Call or Text (352) 722-5295Gear oil for the 2003-2004 Dodge Ram 5.9L Cummins
Diesel Hub's maintenance schedule for the 5.9L Cummins trucks lists about 2.45 qt in the 9.25 front axle and about 3.8 qt in the 11.5 rear, changed every 15,000 miles under severe service. The warning sign of trouble is a whine or howl, and on these axles that comes from running low on fluid. Keep the level up and the grade right and the differentials have little else to ask of you.
Picking a grade
75W-90 synthetic is the grade the schedule lists for both axles. 75W-140 synthetic is the heavier option for the rear, and it is the grade finned aftermarket covers are paired with on towing trucks. This collection also stocks 80W-90, 80W-110 and 85W-140 oils. Those aren't the grades in the factory schedule for these axles, so check your owner's manual, or the instructions for your aftermarket cover, before you pick one of them.
What we carry
- Hot Shot's Secret Blue Diamond HD synthetic gear oil in 75W-90, 80W-110 and 85W-140.
- Hot Shot's Secret Adrenaline synthetic racing gear oil in 75W-90, 80W-110 and 85W-140.
- Lucas Oil 10047 Synthetic 75W-90 and 10121 Synthetic 75W-140, plus 10043 Heavy Duty 80W-90 and 10042 Heavy Duty 85W-140.
- Royal Purple 01301 Max-Gear 75W-140 synthetic.
Fitment notes
Gear oil isn't year-specific the way a cover is, but quantity and grade are. Front-axle fluid only applies to 4x4 trucks. If your rear tag says 10.5 rather than 11.5, the capacity is smaller, about 2.65 qt. Verify by VIN if you're not sure which axles are under the truck.
Frequently asked questions
How much gear oil do I need to service both axles?
A little over 6 qt: about 2.45 qt for the 9.25 front and about 3.8 qt for the 11.5 rear. An aftermarket cover with more capacity will take more, so buy extra if you've added one.
Can I run 75W-140 in the front axle?
The factory schedule lists 75W-90 GL-5 synthetic for the 9.25 front and keeps the 75W-140 option for the rear. Stick with 75W-90 up front unless your owner's manual says otherwise.
How often should I change differential fluid?
Every 15,000 miles under severe service, per Diesel Hub's schedule for these trucks. For lighter use, follow the interval in your owner's manual.
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.