Riddle: Why are 99% front/rear diff covers a nice, matched pair?

[ArmyRN]

I've got a 23 JLU Willys XR 2.0T. Last fall I had TrueTracs installed front and rear. The installer (whos been doing this for literally decades) thought the gear oil smelled or looked burnt. Maybe also something off the factory LS clutch plates? I had been doing some hard towing with the Jeep prior, and I know folks report these M220 diffs running hot.

So I ordered this rear diff cover in raw aluminum for insurance. I'm not going for looks (it'll still look nice) so much as I am function. Hopefully it'll run cooler once installed. I wonder if the ones that are powdercoated keep in some of the heat(?). And the raw ones are cheaper. With my military discount it came to $226.00 total. Should be here 8 Feb.

https://www.oreillyauto.com/detail/...12-bolt-hole-differential-cover/afey/4671000a

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[autotragic]

Not entirely. Most vehicles have two different windshield wipers. Very little is actually symmetrical, when you get right down to it.

I could use some new diff covers in the next 48 hours, and I was curious what people thought about mismatching them.

I’m leaning towards the Spicer nodular iron, certainly in the rear. Probably both. But the ARBs are nice too.

I’m just stopping to appreciate that functionally they do different things, front vs. rear.

Counterpoint; the stock front differential cover is fine and what you actually need is a front differential skid plate.

Then put whatever floats your boat on the back.

For what it's worth I bought two ARB diff covers (red of course) and then realized what I just told you.

 

[Tncdrew]

Here's an idea...
Learn to wheel so that you're not ramming your diff covers into rocks! Pretty simple concept.

 

[grimmjeeper]

Here's an idea...
Learn to wheel so that you're not ramming your diff covers into rocks! Pretty simple concept.

Or better yet, don't leave the road so you don't hit the diffs.

If you do any significant wheeling, you're going to hit your diff. You can even have a significant impact on the rear diff backing down off an obstacle.

Bottom line, if you are going to do serious trails, you're going to drag your diffs and likely hit them sooner or later.

 

[Terrymo]

Or better yet, don't leave the road so you don't hit the diffs.

If you do any significant wheeling, you're going to hit your diff. You can even have a significant impact on the rear diff backing down off an obstacle.

Bottom line, if you are going to do serious trails, you're going to drag your diffs and likely hit them sooner or later.

The gouges on my diff skids, various other skids, and skids on my skids, prove I have a lot of learning to do. But that’s why I’m out there off-roading with people who are good at it. Hopefully I make slightly better choices every time

 

[WontonJLUR]

The gouges on my diff skids, various other skids, and skids on my skids, prove I have a lot of learning to do. But that’s why I’m out there off-road ing with people who are good at it. Hopefully I make slightly better choices every time

If you're actually pushing the limits of yourself, and your Jeep, you're going to hit the diffs on things. If you're driving around on greens and think you can completely avoid hitting the diff on things 100% of the time, well....

 

[grimmjeeper]

The gouges on my diff skids, various other skids, and skids on my skids, prove I have a lot of learning to do. But that’s why I’m out there off-road ing with people who are good at it. Hopefully I make slightly better choices every time

You assume, incorrectly, that you can avoid the axle touching the rocks. The only way to fully avoid that is to not go off road.

If you go off road over rocks you're going to drag or hit the diff (or both) sooner or later. Even the most experienced people will touch diffs off and on. Best bet is to armor your diffs front and rear and then you don't have to worry about it.

 

[Terrymo]

You assume, incorrectly, that you can avoid the axle touching the rocks. The only way to fully avoid that is to not go off road.

If you go off road over rocks you're going to drag or hit the diff (or both) sooner or later. Even the most experienced people will touch diffs off and on. Best bet is to armor your diffs front and rear and then you don't have to worry about it.

Maybe intended for someone else or I’m just confused but that’s ok
I assume I’m going to hit everything and my first investments were skids because unlike Rainman I’m not a “very good driver”…offroad.

Or you mean if I’m progressing and doing harder things I’ll continue to hit my skids? Yes I agree.

 

[zouch]

the functional requirement for me was to keep the diff carrier from flexing under the torque of a diesel turning 37s via 4.56s.
that issue was the same for front and rear.

for that reason, nodular was my first choice.

i'm not towing, and change the dif fluid often enough that even after my worst runs it's come out clean and unburnt, even running the non-Synthetic Eaton wants me to use. based on that, i wasn't concerned about needing the heat dissipation characteristics of aluminum.
i generally manage to keep from hitting anything hard forcefully, so wasn't worried about breaking a cover; therefore wasn't worried about using the Nodular covers. were that a concern of mine, i'd add skids there. (i already have a full belly pan and skids most everywhere else.)

Dana makes a decent set of covers, and they should know how to make covers that fit their axles and provide proper internal fluid flow; made my choice easy. (helps that i don't have to get them in some stupid color.)

matching axles front and rear, matching primary concerns front and rear; matching dif covers front and rear. were i to have a CDO issue, it would be happy,

Seems to me that, objectively:

• A front diff cover should be made of welded carbon steel that (when bashed on a rock) might deform. Or it might survive a hit. By contrast, aluminum or nodular iron might fail, since they’re strong but more brittle (iron) or light and good at cooling (milled aluminum). The front pumpkin is the lowest hanging metal thing, and it goes first. It leads. It’s like the bulbous bow sitting below the waterline of a gigantic ocean-going ship. Yet less is asked of the gear oil up front, and thus less is asked of the cooling.
• A rear diff cover will primarily hit rocks at the rim (or on the drain plug… but I digress). Yet much is asked of the gear oil back there, and thus much is asked of the cooling. It should be made of nodular iron, perhaps.

You only ever see these things marketed in identical pairs, though.

Seems to me most vehicles should have dissimilar metals, front vs. back. The functional requirements are inherently dissimilar.

Am I wrong?

 

[Kracka]

I've got a 23 JLU Willys XR 2.0T. Last fall I had TrueTracs installed front and rear. The installer (whos been doing this for literally decades) thought the gear oil smelled or looked burnt. Maybe also something off the factory LS clutch plates? I had been doing some hard towing with the Jeep prior, and I know folks report these M220 diffs running hot.

So I ordered this rear diff cover in raw aluminum for insurance. I'm not going for looks (it'll still look nice) so much as I am function. Hopefully it'll run cooler once installed. I wonder if the ones that are powdercoated keep in some of the heat(?). And the raw ones are cheaper. With my military discount it came to $226.00 total. Should be here 8 Feb.

https://www.oreillyauto.com/detail/...12-bolt-hole-differential-cover/afey/4671000a

Great price, you'll love it! I'm personally a fan of Redline gear oil for it's thermal stability, but plenty of other good choices too.

You could actually get real crazy and do a heat-dispersant coating on it so it looks good and remains 100% functional.

I used to do black thermal dispersant coatings on aluminum intake manifolds back in the day.

 

[gato]

Seems to me most vehicles should have dissimilar metals, front vs. back. The functional requirements are inherently dissimilar.

Am I wrong?

Since I built my JL during the pandemic shortages, I could not find the G2 covers that I wanted for both front/rear, so I had to go with dissimilar ones - G2 front, Metalcloack rear.

You do need to remember that on rocky trails, where diff covers are most important, we do move forwards and back, and roll back when trying to clear obstacles quite often. So they both get bashed in both directions. Also, one of the key functions of aftermarket diff covers is to add strength/rigidity to the axle diff housing. Any hit that is strong enough to crack a thick aftermarket housing would probably do damage to the axles anyway.

 

[CableDaddy]

Metalcloak front/rear and skids for both. Never had a problem with my old SOLID covers on my old ‘12 JK, nor my PR44 cover for it when I swapped out my d30 and those are nod iron so I wasn’t concerned with nodular iron for the JL.

I was however concerned that a buddy of mine didn’t have skids and he and over the years worn his diff thin on his rear axle so I sprung for them on mine. Handled the dusy easy enough.

No worries at all from my view point.

 

[Fatbob Frank]

Not entirely. Most vehicles have two different windshield wipers. Very little is actually symmetrical, when you get right down to it.

I could use some new diff covers in the next 48 hours, and I was curious what people thought about mismatching them.

I’m leaning towards the Spicer nodular iron, certainly in the rear. Probably both. But the ARBs are nice too.

I’m just stopping to appreciate that functionally they do different things, front vs. rear.

I bought a set of Spicer covers too and plan to switch them when I do the first fluid change this spring.
Frankly, I doubt anyone but a hard core Jeeper would notice if you ran different diff covers, but my OCD would nag me...

 

[kah.mun.rah]

IMO at the end of the day I don't think the difference makes enough of a difference. If you are towing maybe get something in the rear to help with cooling. If you plan to do a lot of rock crawling, get some dif skids. Beyond that I wouldn't put too much thought or worry into it. So many Jeep mods are bought out of fear that the stock parts are going to explode if driven on a dirt road. People would be surprised at how strong stock parts actually are and how less of an extreme off-roader they actually are in reality vs how they imagine themselves to be after watching YouTube videos.

 

[DarthAWM]

Most consider nodular iron more that strong enough, but if, you worry there is always Spider diff gaurds
https://purplecranium.com/c-53685-axle-armor-covers-spider-differential-rock-guards.html

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