Ram 1500 · Elgin CDJR · Streamwood, IL
Ram 1500 Differential Fluid Guide
What gear oil goes in the front and rear differentials of a Ram 1500, and when should it be changed? Here is what the 2026 Ram 1500 owner's manual says about the axle lubricant for each axle, the limited-slip additive, checking the level and when the axle fluid should be changed.
75W-85Front axle, GL-5 synthetic
75W-90C235 rear (3.21/3.55) and RB260 rear
75W-140C235 rear with 3.92 ratio
5 ozLimited-slip additive
The short answer
The 2026 Ram 1500 owner's manual recommends Mopar GL-5 Synthetic Axle Lubricant SAE 75W-85 for the front axle. For the rear axle it recommends Mopar Synthetic Gear Lubricant SAE 75W-90 (MS-A0160) for the C235 rear axle with 3.21 or 3.55 gearing and for the RB260 rear axle (3.92), and Mopar Synthetic Gear Lubricant SAE 75W-140 (MS-8985) for the C235 rear axle with 3.92 gearing. Limited-slip rear axles also require 5 oz. (148 ml) of Mopar Limited Slip Additive (MS-10111).
What differential fluid does a Ram 1500 take?
The manual's Chassis Fluids And Lubricants table lists the lubricant for each axle:
| Axle | Lubricant, per the 2026 manual |
|---|---|
| Front axle (4x4) | Mopar GL-5 Synthetic Axle Lubricant SAE 75W-85 |
| C235 rear axle, 3.21 or 3.55 ratio | Mopar Synthetic Gear Lubricant SAE 75W-90 (MS-A0160); limited-slip axles add 5 oz. (148 ml) Mopar Limited Slip Additive (MS-10111) |
| C235 rear axle, 3.92 ratio | Mopar Synthetic Gear Lubricant SAE 75W-140 (MS-8985); limited-slip axles add 5 oz. (148 ml) Mopar Limited Slip Additive (MS-10111) |
| RB260 rear axle, 3.92 ratio | Mopar Synthetic Gear Lubricant SAE 75W-90 (MS-A0160); limited-slip axles add 5 oz. (148 ml) Mopar Limited Slip Additive (MS-10111) |
Which rear axle and gear ratio your truck has depends on how it was built; an authorized dealer can confirm it from the vehicle. The same table lists Mobil Fluid LT for the 48-11 Active On-Demand transfer case (with 4WD AUTO) and Shell Spirax S2 ATF A389 for the 48-12 part-time transfer case (without 4WD AUTO), which are separate from the axle lubricant.
From the 2026 Ram 1500 owner's manual (Chassis Fluids And Lubricants), read November 8, 2026.
Limited-slip differential additive
The manual says rear axles equipped with a Limited Slip Differential require that 5 oz. (148 ml) of Mopar Limited Slip Additive be added to the gear lubricant, and that the additive should be added whenever a fluid change is made to an axle equipped with a Limited Slip Differential.
When refilling a limited slip differential axle which requires a friction modification additive, it says the additive should be added before the gear lubricant to ensure proper additive fill.
From the 2026 Ram 1500 owner's manual (Rear Axle And 4x4 Front Driving Axle, Lubricant Selection, Limited-Slip Differentials; Chassis Fluids And Lubricants), read November 8, 2026.
How to check the Ram 1500 differential fluid level
For normal service, the manual says periodic fluid level checks are not required. When the vehicle is serviced for other reasons, the exterior surfaces of the axle assembly should be inspected, and if gear oil leakage is suspected, the fluid level should be inspected with the vehicle in a level position.
The fluid level should be even with the bottom of the fill hole, within 1/4 in (6.4 mm) of the edge of the hole, for both the front axle and the rear axle.
From the 2026 Ram 1500 owner's manual (Rear Axle And 4x4 Front Driving Axle, Fluid Level), read November 8, 2026.
How often to change Ram 1500 differential fluid
The manual says to refer to the Maintenance Plan for the drain and refill interval. Its Additional Inspections list this item every 30,000 miles (48,000 km) or 3 years, whichever comes first: inspect the front and rear axle surfaces; if gear oil leakage is suspected, check the fluid level; and if using your vehicle for police, taxi, fleet, off-road or frequent trailer towing, change the axle fluid.
The plan also notes that more frequent maintenance may be needed in severe conditions, such as dusty areas and very short trip driving.
From the 2026 Ram 1500 owner's manual (Maintenance Plan, Additional Inspections; Rear Axle And 4x4 Front Driving Axle, Drain And Refill), read November 8, 2026.
Water in the axle
The manual notes that the presence of water in the gear lubricant will result in corrosion and possible failure of differential components. Operation of the vehicle in water, as may be encountered in some off-highway types of service, will require draining and refilling the axle to avoid damage.
From the 2026 Ram 1500 owner's manual (Rear Axle And 4x4 Front Driving Axle, Lubricant Selection), read November 8, 2026.
Ram 1500 service at Elgin CDJR
If your Ram 1500 tows often, goes off-road or has been through deep water, our Ram service center can inspect the axles and change the differential fluid with the lubricant the manual calls for. Our service department is open Monday to Friday 7 a.m. to 7 p.m. and Saturday 7:30 a.m. to 4 p.m., and is closed Sunday. Elgin CDJR is at 1500 W. Lake St. in Streamwood. Get directions.
Ram 1500 Differential Fluid FAQ
What gear oil goes in a Ram 1500 front differential?
The 2026 manual recommends Mopar GL-5 Synthetic Axle Lubricant SAE 75W-85 for the front axle.
What gear oil goes in a Ram 1500 rear differential?
It depends on the axle: SAE 75W-90 (MS-A0160) for the C235 rear axle with 3.21 or 3.55 gearing and for the RB260 rear axle, and SAE 75W-140 (MS-8985) for the C235 rear axle with 3.92 gearing.
Does the Ram 1500 need limited-slip additive?
Rear axles with a Limited Slip Differential require 5 oz. (148 ml) of Mopar Limited Slip Additive (MS-10111), added before the gear lubricant whenever the fluid is changed.
How often should I change the differential fluid on a Ram 1500?
Every 30,000 miles (48,000 km) or 3 years, the Maintenance Plan says to inspect the axle surfaces and to change the axle fluid if the truck is used for police, taxi, fleet, off-road or frequent trailer towing.
How full should a Ram 1500 differential be?
Even with the bottom of the fill hole, within 1/4 in (6.4 mm) of the edge of the hole, for both the front and rear axle, checked with the truck level.
What are your service hours?
Monday to Friday 7 a.m. to 7 p.m. and Saturday 7:30 a.m. to 4 p.m. We are closed Sunday.
Bring your Ram 1500 to Streamwood
Visit Elgin CDJR at 1500 W. Lake St. in Streamwood.
Sources
The guidance on this page is from the 2026 Ram 1500 owner's manual on Mopar (PDF dated February 12, 2026), read November 8, 2026. Our address and service hours are from our own website, checked the same day.