Differential question here.


Asked by Jun 09, 2017 at 10:30 PM

Question type: Maintenance & Repair

Differential question here. Not for me though lol  I have a friend who has a 2006 Dodge Ram 1500 like mine. He wants to change the oil in his rear differential. The spec calls for 75w-90 oil. Is it safe to use 85w-140 instead. I know it is thicker but I could not give him a definitive answer. Any gear heads out there have opinions on this?

3 Answers


My Ford 9.75 "rear differential calls for 85W-140 and I have 188,000 miles on it and the gears still look like new. I would read the owners manual from the Dodge and see exactly what it says. Maybe the heavier oil is called out for "heavy duty" use. The temperature range you operate in will be a factor in what oil is best.

1 people found this helpful.

Finally nailed down the answer to this. 75W-140 is the gear oil to use. Synthetic is preferred. And it requires an additive for limited slip. I have seen some gear oils that already have this in it so you may be able to skip that. Just make sure you read the label. He went with Royal Purple 75W-140 Max Gear. Very expensive though. But on the bright side it is working super.


I use Lucas synthetic gear oil with Ford limited slip additive but I drive a Ford.

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