Differential oil change

[Fast-n-Furious]

I installed ISS Pro axle temperature gauges shortly after buying my JL. The rear axle temperature is is typically 210°F while running unloaded down the highway at 70MPH in 85°F ambient temperatures.

I have seen it hit 230°F under the same conditions but going 80MPH. At 110°F ambient and 70MPH, I have seen 235°F. Loaded running fast will have the temperatures hitting 240°F.

In the photo below I am going 75MPH @95°F ambient--4.10 gears and 35" tires--unloaded):

Oh man I love seeing the actual data of usage and appreciate it! I do some spirited fun driving occasionally and I’d assume (based on your data) mine might be a bit higher temperature with 4.56 gear ratio and 35” tires.
Thanks for posting the picture, very nice setup and what a fun project!

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[CarbonSteel]

Oh man I love seeing the actual data of usage and appreciate it! I do some spirited fun driving occasionally and I’d assume (based on your data) mine might be a bit higher temperature with 4.56 gear ratio and 35” tires.
Thanks for posting the picture, very nice setup and what a fun project!

Load and ambient temperatures influence that quite a bit. I am running less temperatures these days in Colorado versus Texas despite my now running 5.13's and 37's plus weighing about 900 pounds more.

 

[XxsullyxX123]

@Rhinebeck01 Just did my first diff oil change front and rear in my Rubicon. Used 75/140 in both front and rear. drain plugs and outgoing oil looked great for 22,500 miles, as I have been gentle on the Jeep aside from 37's. What a great recommendation on those valvoline flexfill bags. it really couldn't have been easier!

 

[Fast-n-Furious]

So I got the diff covers replaced today. Went with RuffStuff 1/4” thick ring and 3/8” cover. Really beefy and beautifully welded. Quality hardwares. Perfect fitment as well.

At 7500 miles, the rear fluid pretty dark already with normal metal shaving at the refill plug magnet.

I cleaned and reused the gaskets. Refilled 75W-140 per @Rhinebeck01 recommendation. Thanks again. The FlexFill pouch worked well and I also jacked up the frame to gain more clearance which also helped when torquing the bolts. It was my fault that didn’t plan very well. I refilled two pouches in rear and still didn’t see the level close to the refill hole. Did a bit search on the capacity again. Pumped about 0.4-0.5 quart out to use for front.

I had to Jack up the frame near driver side front for room to work on the bolts. Refilled one whole pouch, then used 0.3 ish pumped out from the rear diff. It’s hard to measure the exact volume just by looking at the pouch. But I think I got the balance as close as I could. So 1.6 quart rear and 1.3qt front. Spilled a bit but should be fine.

Torqued the 12-point bolts to 25 foot-pound using my harbor freight torque wrench which I think should be fine.

All in all, took me 4 hours. I did not rush and I’m very happy about the end result. Not sure if any mpg difference with using 75W-140. My 392 only gets me 13.5 mpg on average and I can live with it.

 

[Fast-n-Furious]

@Rhinebeck01 and @CarbonSteel , not sure if there’s an agreed answer. I’ve seen lots discussions on the amount of gear oil to refill for the aftermarket diff covers. Some say refill to the refill port level and others go with manufacturers capacity.

Before I took off the factory diff covers today, I checked the oil level through the refill port and it’s at least 1/2” or more below the refill port. I didn’t measure because I don’t have a measuring cup available. Some people also pointed that some of the oil may still in reside in the axle.

Personally I’m included to follow the manufacturer spec because different aftermarket diff covers have different inner design and the refill ports may be placed at different height.

What are your insights on this? I’d imagine the diff ring gear always picks up the oil and throw it up so it doesn’t matter much if the refill amount is a bit more or less than spec capacity. Still want a more scientific reasoning which I couldn’t find online.

 

[CarbonSteel]

@Rhinebeck01 and @CarbonSteel , not sure if there’s an agreed answer. I’ve seen lots discussions on the amount of gear oil to refill for the aftermarket diff covers. Some say refill to the refill port level and others go with manufacturers capacity.

Before I took off the factory diff covers today, I checked the oil level through the refill port and it’s at least 1/2” or more below the refill port. I didn’t measure because I don’t have a measuring cup available. Some people also pointed that some of the oil may still in reside in the axle.

Personally I’m included to follow the manufacturer spec because different aftermarket diff covers have different inner design and the refill ports may be placed at different height.

What are your insights on this? I’d imagine the diff ring gear always picks up the oil and throw it up so it doesn’t matter much if the refill amount is a bit more or less than spec capacity. Still want a more scientific reasoning which I couldn’t find online.

I fill it to the bottom of the fill port since most, if not all, aftermarket overs have slightly different shapes versus OEM and thus the capacity is also different from the OEM specifications.

It may be a bit more than the OEM but better to have that versus not enough.

 

[Fast-n-Furious]

I fill it to the bottom of the fill port since most, if not all, aftermarket overs have slightly different shapes versus OEM and thus the capacity is also different from the OEM specifications.

It may be a bit more than the OEM but better to have that versus not enough.

I got an answer from RuffStuff Specialities:

We do not design them to have more fluid capacity. Me personally, have always put about an 1/8th of a quart over with our cover. You do not want to fill it to the fill plug.

So I think mine should be good.

 

[quick66]

Changed the front and rear diff fluid in my 2022 JLU XR today. I was surprised that there were no drain plugs. mine only has fill plugs on both diffs. I had to remove the inspection covers on both front and rear to drain the fluid. It looked like the factory used red loctite on the cover bolts. Anyone else ran in this?

Good news both gears sets looked great at 5,600 miles. Some off-roading and light towing nothing too hardcore so far. I used Royal Purple 75w-140 in both front and rear. Pretty easy job would have helped to have a 10mm wratchet wrench to get to the upper bolts on the front cover. I will definitely have one next time. I will also install some aftermarket covers with drain plugs when the next service is due. Thanks to the OP and other contributors to this thread.

 

[Newbalewb]

I got an answer from RuffStuff Specialities:



So I think mine should be good.

Not being designed to fill to the fill port seems like a pretty dumb design...

 

[CarbonSteel]

I got an answer from RuffStuff Specialities:



So I think mine should be good.

Strange since it is basically a clone of Motobilt and they just say "fill the differential with oil".

If it is over the OEM level it should be totally fine.

 

[Jtclayton612]

Changed the front and rear diff fluid in my 2022 JLU XR today. I was surprised that there were no drain plugs. mine only has fill plugs on both diffs. I had to remove the inspection covers on both front and rear to drain the fluid. It looked like the factory used red loctite on the cover bolts. Anyone else ran in this?

Good news both gears sets looked great at 5,600 miles. Some off-roading and light towing nothing too hardcore so far. I used Royal Purple 75w-140 in both front and rear. Pretty easy job would have helped to have a 10mm wratchet wrench to get to the upper bolts on the front cover. I will definitely have one next time. I will also install some aftermarket covers with drain plugs when the next service is due. Thanks to the OP and other contributors to this thread.

Think the disappearance of the drain plugs happened in 2021 or most of the way through 2020 iirc. Totally normal

 

[Fast-n-Furious]

Strange since it is basically a clone of Motobilt and they just say "fill the differential with oil".

If it is over the OEM level it should be totally fine.

Motobilt has this page saying to follow the capacity chart: https://motobilt.com/blogs/first-blog/jeep-wrangler-differential-fluid-capacity-chart

 

[CarbonSteel]

Motobilt has this page saying to follow the capacity chart: https://motobilt.com/blogs/first-blog/jeep-wrangler-differential-fluid-capacity-chart

On that same page they say this:

"Well the general rule of thumb is to fill your diff up until the fluid starts to run out the fill hole."

and this:

"With the after market covers we make you may find that they hold slightly more than the factory specs listed below."

Hence the reason I fill it to the bottom of the fill hole. Nothing is going to happen by doing that.

 

[JLR_AEV]

So I got the diff covers replaced today. Went with RuffStuff 1/4” thick ring and 3/8” cover. Really beefy and beautifully welded. Quality hardwares. Perfect fitment as well.

At 7500 miles, the rear fluid pretty dark already with normal metal shaving at the refill plug magnet.

I cleaned and reused the gaskets. Refilled 75W-140 per @Rhinebeck01 recommendation. Thanks again. The FlexFill pouch worked well and I also jacked up the frame to gain more clearance which also helped when torquing the bolts. It was my fault that didn’t plan very well. I refilled two pouches in rear and still didn’t see the level close to the refill hole. Did a bit search on the capacity again. Pumped about 0.4-0.5 quart out to use for front.

I had to Jack up the frame near driver side front for room to work on the bolts. Refilled one whole pouch, then used 0.3 ish pumped out from the rear diff. It’s hard to measure the exact volume just by looking at the pouch. But I think I got the balance as close as I could. So 1.6 quart rear and 1.3qt front. Spilled a bit but should be fine.

Torqued the 12-point bolts to 25 foot-pound using my harbor freight torque wrench which I think should be fine.

All in all, took me 4 hours. I did not rush and I’m very happy about the end result. Not sure if any mpg difference with using 75W-140. My 392 only gets me 13.5 mpg on average and I can live with it.

Good stuff!

I don't know if you mentioned this but did you pott your locker sensors while you were in there? Def something that should be done for all Rubicons on stock lockers ?

 

[quick66]

Think the disappearance of the drain plugs happened in 2021 or most of the way through 2020 iirc. Totally normal

That’s a bummer. I thought about this more last night. I’ll have to pull the cover each time I need to service the diff as there appear to be no after market covers with drain plugs. That makes sense because you would never be able to get the drain plug low enough on the cover to drain all the old fluid. These is my first Jeep and first time working on mopar diffs. I’ve worked on 12 bolt Chevrolet diffs a lot and they always had a drain plug built into the center section.

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