Check your rear diff fluid level

[UnloosedChewtoy]

In the old days (and I expect yet today) fluid was properly filled when you could put your little finger in the hole, bend the finger down and you could touch the fluid. Filling all the way to the base of the fill file could cause the fluid to be over full when hot. Can contribute to leaks.

I do remember that. However, a touch low is one thing, but half a quart is a bit much when the entire capacity is less than 3 quarts.

 

[cj7]

In the old days (and I expect yet today) fluid was properly filled when you could put your little finger in the hole, bend the finger down and you could touch the fluid. Filling all the way to the base of the fill file could cause the fluid to be over full when hot. Can contribute to leaks.

They’ve since learned to put the fill lower, so you don’t have to stick anything inside (avoiding FOD). Proper filling here is to the lower edge of the fill hole.

That said, the rear diff prob doesn't really need to be at 2.85 gts, hence the factory fill at 2 qts. But I see no harm in filling to the bottom of the fill hole.

 

[wallyuwl]

Appreciate the heads up on this. Just checked mine today at 5,000 miles, sure enough it was about half an inch below the fill hole. Put just over a half quart in to top it off. A bit concerning something that takes as much abuse as a differential would come under filled from the factory.

Decided I might as well check the front too, it was low also. Only added maybe 15-20oz to it before it was full though.

I checked my front differential today. Nothing came out after removing the fill plug, but as soon as I put some in it drained out. So the front was full from the factory. The front fill plug was also 8mm hex, just like the rear. The plug no thread sealant on it, so I just put it back on.

For those looking for how to do the front, it is the same as the back but here is a good short video.

 

[wallyuwl]

I just looked at the manual on the Ram app. Unless you have 3.92, the recommended fluid is 75W-90, not 75W-140. I have 3.21 and the rear diff and it took a little over half quart. I used 75W-140. Should I do a complete drain and fill with the 75W-90, or is having a little 75W-140 ok?

 

[cj7]

I just looked at the manual on the Ram app. Unless you have 3.92, the recommended fluid is 75W-90, not 75W-140. I have 3.21 and the rear diff and it took a little over half quart. I used 75W-140. Should I do a complete drain and fill with the 75W-90, or is having a little 75W-140 ok?

It’s fine, no worries at all.

 

[wallyuwl]

It’s fine, no worries at all.

Didn't think so but making sure. The 75W-140 is more robust anyway. I have seen some people switch to this from 75W-90 when doing a full change, and stated lower differential temps and better performance. Is it advisable to switch weights when I do the full drain and fill (probably in a year)?

 

[cj7]

A good quality synthetic hypoid gear oil of the recommended viscosity is fine. If you want, you can go to the 75w-110 in your 3.21, which some use for frequent towing. You could go to -140, but not sure you’d see any benefit beyond the -110.

Truth is, any of them will work, if filled properly and if changed at least as often as recommended. Use Red Line, or Valvoline, or similar and if you can, one that that explicitly lists the Mopar standard or Mopar fluid part number on the bottle.

 

[wallyuwl]

A good quality synthetic hypoid gear oil of the recommended viscosity is fine. If you want, you can go to the 75w-110 in your 3.21, which some use for frequent towing. You could go to -140, but not sure you’d see any benefit beyond the -110.

Truth is, any of them will work, if filled properly and if changed at least as often as recommended. Use Red Line, or Valvoline, or similar and if you can, one that that explicitly lists the Mopar standard or Mopar fluid part number on the bottle.

Thx. I plan to use Valvoline, it is inexpensive and readily available and I like the pouches. It doesn't come in 75w-110. Only the -140 lists the Mopar part number, not -90.

So final interpretation is 75w-140 will be just fine, and maybe even help a little with wear (but maybe a slight hit to mpg), vs 75w-90 in the 3.21?

 

[warri]

Does this binding sound come from the front wheels when turning sharply? When I do a full wheel turn i often here what sounds like "rubbing"

 

[Hemidakota]

Does this binding sound come from the front wheels when turning sharply? When I do a full wheel turn i often here what sounds like "rubbing"

Do you have bigger tires? Sounds like rubbing on the inner fender liner

 

[c3k]

Planning on doing front and rear diffs in the next couple of days.

I've got 4 ramps, so that'll make it easy. I'm using Mobil1 75w90, front and rear (3.21 rear). 5,500 miles, but I want to make sure both diffs are filled (and remove any break-in swarf). I'm allocating 60 minutes to the job, for both, and that includes a cup of coffee afterwards.

 

[cevans6318]

In the old days (and I expect yet today) fluid was properly filled when you could put your little finger in the hole, bend the finger down and you could touch the fluid. Filling all the way to the base of the fill file could cause the fluid to be over full when hot. Can contribute to leaks.

that is not true at all. filling to the bottom of the fill hole is what is expected when filling the rear diff. most all manuals tell you this. the fluid is not gonna expand to the point you are gonna start having leaks when you fill it to the bottom of the fill hole

 

[warri]

Do you have bigger tires? Sounds like rubbing on the inner fender liner

Stock Laramie Night edition

 

[wallyuwl]

Planning on doing front and rear diffs in the next couple of days.

I've got 4 ramps, so that'll make it easy. I'm using Mobil1 75w90, front and rear (3.21 rear). 5,500 miles, but I want to make sure both diffs are filled (and remove any break-in swarf). I'm allocating 60 minutes to the job, for both, and that includes a cup of coffee afterwards.

Look at the table. Mot sure how important this is..

https://www.amsoil.com/p/severe-gear-75w-90-svg/

 

[c3k]

Look at the table. Mot sure how important this is..

https://www.amsoil.com/p/severe-gear-75w-90-svg/

Lol. I like Amsoil. But...I already had 5 quarts of Mobil1 75w90 in my garage from a previous front differential (son's). Soo...I'll use Mobil1 this time, and probably swap to Amsoil Severe Gear the next time I decide to change the lube.

Thanks!

 

[bigdodge]

that is not true at all. filling to the bottom of the fill hole is what is expected when filling the rear diff. most all manuals tell you this. the fluid is not gonna expand to the point you are gonna start having leaks when you fill it to the bottom of the fill hole

"Check the fluid level with your finger. The gear oil in the rear differential should reach the bottom of the service port hole. Insert one finger into the open service port. Bend your finger downward slightly to see if it comes into contact with gear oil.[11]

• If your finger touches gear oil, there is enough fluid inside.
• If the fluid level doesn't reach the service port, it is low."

How to Check Your Car's Differential Gear Oil: 13 Steps

The gears inside your car's differential enable the drive wheels to spin at the right speed when you step on the gas pedal and at different rates when you turn a corner. The gears are coated with a film of oil that protects the hardened...

www.wikihow.com

is this what you mean?
because this might be what rc turner was saying.

which is how i do check it. and have been for 50 year.

 

[1D32319]

Timely post. I had been planning the front and rear change to Amsoil until after I got new tires.

Got new tires today, so maybe I'll do it this weekend.

 

[Bw1605]

I gotta order it, Amsoil, gonna do front and rear since I tow a camper regularly, just gotta figure out weight and if I have limited slip. My old eco diesel didn’t have limited slip so differential change was simple.

 

[1D32319]

I gotta order it, Amsoil, gonna do front and rear since I tow a camper regularly, just gotta figure out weight and if I have limited slip. My old eco diesel didn’t have limited slip so differential change was simple.

Owner's manual is pretty good about the weight per configuration-several variations. Your window sticker or build sheet should have gear ratio and whether or not it is a limited slip diff. Amsoil page is pretty good about capacity as well.

 

[Bw1605]

Owner's manual is pretty good about the weight per configuration-several variations. Your window sticker or build sheet should have gear ratio and whether or not it is a limited slip diff. Amsoil page is pretty good about capacity as well.

I got the weights right and ordered. I have 3.92 no max tow. Gotta find out if it’s limited slip though. Don’t think it is but not 100% either