Differential oil change

[Fast-n-Furious]

When I had my WJ about 20 years ago, I used an extractor pump to remove the fluid from the rear diff. I did so because I was afraid that by removing the bolts and popping it open, it would leak afterwards or I would mess something up. Mind you, this is when they didn't have fancy gaskets you could put around the diff; you had to use the gasket seal.

On the second oil change on that WJ, I decided to open the diff up and I was glad I did. I was able to clean all the muck off the cover and get all the oil out. I think most of the contamination sits at the bottom, where the oil extractor would have a hard time reaching.

In the end, on that WJ, I was glad I stopped using the extractor and just opened the diff covers. I would make sure you have a torque wrench around though so you know how much to tighten the bolts, and tighten them evenly. It's not that bad of a job and the worst part is the smell of the oil.

Thank you for sharing your experience! I've decided to open the diff cover and now I'm also looking at aftermarket diff covers. I have all the tools needed. I'm also thinking that for the new diff covers, no drain plug can be a good thing. I've done lots of plumbing projects around the house and had some nerve wrecking moments too, eventually all the leaks gone. So I'll take it as an opportunity to know better about my JL.

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[CarbonSteel]

@Fast-n-Furious - this is a very simple job that short of not torquing a cover bolt correctly there is little that can go wrong. The gasket is 100% reusable and is rubber encapsulated steel.

Take your time and it will be a snap. Use lint free towels to wipe out the goop that will inevitably be deposited at the bottom of the pumpkin and do not spray anything into it like brake cleaner.

Any 75W-140 oil will serve you well such as Valvoline, Mobil 1, Castrol, etc. which are readily available most anywhere.

 

[nU7OuxIx]

@Fast-n-Furious - this is a very simple job that short of not torquing a cover bolt correctly there is little that can go wrong. The gasket is 100% reusable and is rubber encapsulated steel.

Take your time and it will be a snap. Use lint free towels to wipe out the goop that will inevitably be deposited at the bottom of the pumpkin and do not spray anything into it like brake cleaner.

Any 75W-140 oil will serve you well such as Valvoline, Mobil 1, Castrol, etc. which are readily available most anywhere.

One question I did have, as I'm going to be doing this soon. When I've done this before, the gaskets were disposable so I didn't care how I opened it. Since this gasket is reusable, do you have any tips about how to pry the cover open without damaging the gasket?

 

[CarbonSteel]

One question I did have, as I'm going to be doing this soon. When I've done this before, the gaskets were disposable so I didn't care how I opened it. Since this gasket is reusable, do you have any tips about how to pry the cover open without damaging the gasket?

Use a large screwdriver and gently pry at the top (not the bottom) and the cover will literally fall off. Leave a couple of bolts loose in the bottom so that the cover does not fall off and make a big mess.

 

[nU7OuxIx]

Use a large screwdriver and gently pry at the top (not the bottom) and the cover will literally fall off. Leave a couple of bolts loose in the bottom so that the cover does not fall off and make a big mess.

I'm wondering if a plastic trim removal tool would be safer? I suppose the trim tool can damage the rubber gasket as well as a screwdriver would.

 

[CarbonSteel]

I'm wondering if a plastic trim removal tool would be safer? I suppose the trim tool can damage the rubber gasket as well as a screwdriver would.

Perhaps, but you will not/should not be putting a lot of pressure on any of it and the sealing portion of the gasket is a raised rib area in the center of the gasket.

Note this is not like a paper gasket that has been glued on, it is a silicone gasket that will not stick like a paper one will.

One finger will be enough to pry against it...

 

[BDinTX]

Heads up if you replace the diff cover and it comes with new bolts:

1) Remove ONE bolt and match up the threads with the new bolts to make sure the new bolts have the correct threading.

2) Make sure you have a tap to chase/clean the bolt holes and make sure the holes are threaded deep enough for the new bolts.

We have two Jeeps, and I put on four ARB covers.
I had to tap about 1/4" of threads for all of the holes that straddle the axle tube, front and rear.
One of the diff covers had the wrong bolts in the box. Thankfully I discovered that before draining the oil out.

 

[Fast-n-Furious]

@Fast-n-Furious - this is a very simple job that short of not torquing a cover bolt correctly there is little that can go wrong. The gasket is 100% reusable and is rubber encapsulated steel.

Take your time and it will be a snap. Use lint free towels to wipe out the goop that will inevitably be deposited at the bottom of the pumpkin and do not spray anything into it like brake cleaner.

Any 75W-140 oil will serve you well such as Valvoline, Mobil 1, Castrol, etc. which are readily available most anywhere.

Thanks a lot for your encouragement! I had bought 3 FlexFill pouches 75W140 per you guys suggested in this thread. Now I’m doing research on different diff covers.
Glad you pointed out the break cleaner, I had planned to use it actually after watching some videos where it was used.

 

[CarbonSteel]

Thanks a lot for your encouragement! I had bought 3 FlexFill pouches 75W140 per you guys suggested in this thread. Now I’m doing research on different diff covers.
Glad you pointed out the break cleaner, I had planned to use it actually after watching some videos where it was used.

Brake cleaner can cause the seals to deteriorate.

Take a look at Motobilt covers, built like a tank and cost effective.

 

[Fast-n-Furious]

Brake cleaner can cause the seals to deteriorate.

Take a look at Motobilt covers, built like a tank and cost effective.

I looked at Motoblit and also came across this RuffStuff version: https://www.ruffstuffspecialties.co...MI7frbx9zt-gIVCbrICh0PVAZAEAAYASAAEgKyi_D_BwE (M210 front for example). The RuffStuff version is thicker steel and there’s no Logo on it.

 

[CarbonSteel]

I looked at Motoblit and also came across this RuffStuff version: https://www.ruffstuffspecialties.co...MI7frbx9zt-gIVCbrICh0PVAZAEAAYASAAEgKyi_D_BwE (M210 front for example). The RuffStuff version is thicker steel and there’s no Logo on it.

That's a nice one too! I would have no issues running it. If you go for that one, just be sure the bolts are long enough.

 

[Fast-n-Furious]

That's a nice one too! I would have no issues running it. If you go for that one, just be sure the bolts are long enough.

Good point. Also do you know anything about the CavFab one?https://cavfab.com/products/jl-jt-rubicon-rear-m220-diff-cover?variant=40861174333589 More affordable and seems to be as beefy. At one point I was a bit concerning about the heat won’t expand as well with thicker diff wall. But I guess 200 - 250 degree hot won’t matter much. Any insights from your experience?

 

[CarbonSteel]

Good point. Also do you know anything about the CavFab one?https://cavfab.com/products/jl-jt-rubicon-rear-m220-diff-cover?variant=40861174333589 More affordable and seems to be as beefy. At one point I was a bit concerning about the heat won’t expand as well with thicker diff wall. But I guess 200 - 250 degree hot won’t matter much. Any insights from your experience?

The CavFab appears to be the same (more or less) as the Motobilt. My Motobilt have been perfect thus far.

Can you explain what you mean about the heat expanding?

 

[Fast-n-Furious]

The CavFab appears to be the same (more or less) as the Motobilt. My Motobilt have been perfect thus far.

Can you explain what you mean about the heat expanding?

With the gear biting and spinning, the diff fluid gets hot in the range of 200-250 degree roughly. I was wondering if thicker metal wall of the diff cover would keep the heat trapped for a longer time… but I guess it doesn’t matter since it’s not that high temperature.

 

[CarbonSteel]

With the gear biting and spinning, the diff fluid gets hot in the range of 200-250 degree roughly. I was wondering if thicker metal wall of the diff cover would keep the heat trapped for a longer time… but I guess it doesn’t matter since it’s not that high temperature.

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):

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