Rear Differential Oil Change - Fill Location? - SOLVED

[dreinert]

I went to change the rear differential oil tonight but I don't see the fill plug, rubber or otherwise. The I found the drain plug, 14mm on the side of the diff, and you can see the location on the cover where the rubber plug typically in the attached picture.

Any ideas? Did Ram change it for 2019?

2019 Ram Limited 4x4

 

[rah6887]

Unbolt the cover, let it drain, re-tighten, you can use the existing gasket.

 

[dreinert]

Thanks Rah. I found the drain plug but not the fill plug. I could remove the cover to drain it as well as you stated but I don’t see anywhere to refill it once it’s drained.

In the past, there was always a rubber plug in the middle/right of the diff cover and I just re-filled until it came out.

 

[dreinert]

Found it! There is a small plug on the front side of the diff; before draining it I verified it was filled to the bottom of the hole.

Pretty quick to change, I just hit 30k miles.

I believe it was a 9mm hex to remove the fill plug and 14mm to remove the drain plug.

 

[The_Dude]

What kind of oil do you guys recommend for the rear diff with the 3.21 gears. Thanks

 

[Willwork4truck]

Dang I thought I was an over-maintainer. 30K for a diff ain’t much. I’d change tranny fluid or coolant before I changed the rear diff, unless you got it under water or really really towed heavy. But do as you want, the truck won’t mind.

 

[The Critic]

Two questions:

1) Does your truck have the anti-spin rear diff?

2) If so, did you have to add additional friction modifier or was the RL 75W140 adequate by itself?

 

[Drewster]

Some of you guys need to read your owners manual where it specifies the gear oil for the different axles and states you should change the fluid at 30k with frequent towing or commercial use...

Thanks for posting @dreinert! I'm excited that there's a drain *and* fill plug!

 

[jerryw1000]

1) Does your truck have the anti-spin rear diff?
2) If so, did you have to add additional friction modifier or was the RL 75W140 adequate by itself?

I know I'm getting too old. In my last limited slip differential the "modifier" additive was whale oil .
A '78 Chevy Caprice Classic I believe it was.

 

[RunsWithBeer]

I used to change the diff oil in my Durango with a limited slip diff when it would start binding the rear diff and chirping tires on sharp slow turns. It would do so every 25k, but I towed a camper so YMMV. I also had a limited slip diff on my Wrangler (worked amazingly well off-road, wheeling up slippery rocks). I changed it every 30k.

 

[dreinert]

Critic,

1) Yes I do have a LSD

2) The RL 75w140 GL-5 does already contain the friction modifier. I bought the little mopar bottle in case I has any issues but I never did so I never added it.

From Redline's website description of 75w140...

• Popular for cars and light trucks like Ford Mustang and F-150, Toyota Tundra and Sequoia, Jeep Cherokee and Dodge Ram
• Contains additional friction modifiers for suitability with clutch-type limited slip differentials - for most LSDs, no additional friction modifiers are required

As a note the owners manual (2019 - Page 552):
75w140 is for 3.92
75w90 is for the 3.21 or 3.55

 

[The Critic]

Critic,

1) Yes I do have a LSD

2) The RL 75w140 GL-5 does already contain the friction modifier. I bought the little mopar bottle in case I has any issues but I never did so I never added it.

From Redline's website description of 75w140...

• Popular for cars and light trucks like Ford Mustang and F-150, Toyota Tundra and Sequoia, Jeep Cherokee and Dodge Ram
• Contains additional friction modifiers for suitability with clutch-type limited slip differentials - for most LSDs, no additional friction modifiers are required

As a note the owners manual (2019 - Page 552):
75w140 is for 3.92
75w90 is for the 3.21 or 3.55

Thank you.