Lets talk Differential Covers!

[mx5red]

I put on diff covers because people said it strengthened the axle. Hard to verify/quantify that, but ok.
Now people having diff failures pointing to heat, and maybe these big iron covers aren’t so good for that.
I use diff skids and couldn’t imagine grinding my diff when I do hard trails. I have yet to hit the diff cover, though it is possible.
I haven’t used the diff covers to drain oil, I’ve changed them once and I removed covers again to look at gears, so I just as easily could’ve kept the stock covers if I’m doing all that.
I like the ARB cover I have, but caution last time I pulled the cover, the bottom magnetic drain bolt was broken and the magnet was stuck at the bottom, luckily not getting chewed up in the diff.

Sponsored

 

[Rusty PW]

When I had the Power Wagon. I smashed a tree stump that was hiding in some tall weeds. Stopped me so hard. I wondered why the air bags didn't go off. Hit it dead center on the Rock Crusher diff cover.

 

[whiteglad]

My Ram hit a huge rock that was mostly buried next to a short bush on a two-track some years ago. I had a home-made protection plate which was bent against the stock diff cover, but I was saved from further damage and lost lube. Fortunately, I was driving very slowly.
Not all stock diffs have the distinctive shape around the ring gear, such as the 8.75" Mopar, AMC 20, many big trucks, etc. Ram diesel owners have been using the flat back Mag-Hytec cover for 25+ years with no reported issues. The ring gear teeth seem to carry plenty of lube without the encouragement of cover shape. I wonder if the shape is more to lessen the quantity of lube to fill the diff to the desired height, thus saving money for the manufacturer.

 

[ShadowsPapa]

My Ram hit a huge rock that was mostly buried next to a short bush on a two-track some years ago. I had a home-made protection plate which was bent against the stock diff cover, but I was saved from further damage and lost lube. Fortunately, I was driving very slowly.
Not all stock diffs have the distinctive shape around the ring gear, such as the 8.75" Mopar, AMC 20, many big trucks, etc. Ram diesel owners have been using the flat back Mag-Hytec cover for 25+ years with no reported issues. The ring gear teeth seem to carry plenty of lube without the encouragement of cover shape. I wonder if the shape is more to lessen the quantity of lube to fill the diff to the desired height, thus saving money for the manufacturer.

"no reported issues" doesn't mean that they couldn't be driving more miles or getting better life out of them.
Big trucks - hope you are only talking private trucks, pickups, for example. "Big trucks" don't all use hypoid gears and are different animals. So I guess we're talking pickup trucks.

No, the shape isn't to reduce lube - it's to ensure the lube gets to where it's needed the most. There's no reason for MORE lube anyway. It's a wives' tale from years ago that more lube is better. Banks shows and proves it.
Back to shape - you mention the AMC designs - the cover is not flat or square, and is a round shape that follows the ring gear nicely up and around. It's not square and allows lube to get right where it's needed for a Light DUTY axle design.

Please don't compare the designs from the late 1950s to current designs where they have had 60 years of learning and study. Do you really think those AMC differentials were designed for hauling tons of trailer or payload? Used in a car weighing maybe 3300 pounds?
There's no real torque applied to them unless it's drag racing and then the duration is extremely limited. Not a lot of time to get them hot or get the lube hot. How can you compare a light duty car design to anything with real torque and pulling needs. Those never saw any real loads unless you talk of the later Jeeps - and then, payload and towing was a joke.
Besides, if you note, the shape of the AMC differential covers is perfectly round and follows the ring gear well enough. Lube will be thrown right where it's needed and the design of the interior casting is fairly complex itself.
Besides, AMC didn't want lube to go out to the axles like other designs. They didn't want lube tossed out to the axle tubes, so their design was to keep it on the carrier bearings, and thrown up to the pinion gears. The housings have a channel cast into them - complex for lowly little AMC's own design.
AMC 8 7/8 and 7 9/16 axle assembly designs lubricated the axle bearings just like the front wheel bearings of most cars of the era - packed in grease, a seal on each side of the bearing to prevent axle lube from getting to the bearings.
So please, don't compare them. Very different animals.

Here's the seal preventing differential lube from getting to the axle bearings (7 9/16" axle type shown. What some call the "AMC 15") ->

For those looking on - did you know that only people like us call those the "AMC 20" or "AMC 15" (used in 6 cylinder and small displacement cars). AMC didn't use those designations.
AMC referred to their own differentials as the 8 7/8" and the 7 9/16" models.
AMC in later years sold their designs and tooling/equipment to Dana to raise money in the 1980s.
The covers are a nearly perfect hemisphere and follow the ring gear fairly closely.
They were designed in the late 50s/early 60s, I'd have to check my books for the first mention of their open shaft differentials of the final design.

 

[Dougstdig]

I think one of the main worries regarding covers is peeling the lower edge when grinding a differential over a rock. I’m comfortable with my nodular iron teraflex units holding up to this now.

 

[Rusty PW]

My Ram hit a huge rock that was mostly buried next to a short bush on a two-track some years ago. I had a home-made protection plate which was bent against the stock diff cover, but I was saved from further damage and lost lube. Fortunately, I was driving very slowly.
Not all stock diffs have the distinctive shape around the ring gear, such as the 8.75" Mopar, AMC 20, many big trucks, etc. Ram diesel owners have been using the flat back Mag-Hytec cover for 25+ years with no reported issues. The ring gear teeth seem to carry plenty of lube without the encouragement of cover shape. I wonder if the shape is more to lessen the quantity of lube to fill the diff to the desired height, thus saving money for the manufacturer.

A couple of the 3th gen Power Wagon guys with the AAM 10.5" rear diff have lost the pinion bearing.

 

[WilliamD]

I have the nodular iron Dana covers. They have the same inside shape as the stamped oem covers.

Just about any iron cover is better than the oem cover, off road.

Any clearance issues with the track bar? I’m trying to find a width measurement. How far the cover pokes out from the diff.

 

[WilliamD]

If I replaced my cover, this is what I’d go with. Their differential, their cover. Just my preference.

Did you need a rear sway bar spacer or anything for the rear diff to make it fit?

 

[WILDHOBO]

Did you need a rear sway bar spacer or anything for the rear diff to make it fit?

Nope. But my cover is stock. I have next venture motorsports diff skids. Nothing gets near my covers with those.

 

[Josh00333]

Ok fellas, I'm waffling on the rear differential skid.

Install it or return it?

Thing is $380, I am putting on the diff covers.

I'm second guessing the need, cost and weight.



To add, all this work, lift kit, covers, gearing, front locker is all for more trails in Moab.

I've done 90% of the level 4 and below trails, time to explore the 5-7's.

 

[WILDHOBO]

Ok fellas, I'm waffling on the rear differential skid.

Install it or return it?

Thing is $380, I am putting on the diff covers.

I'm second guessing the need, cost and weight.



To add, all this work, lift kit, covers, gearing, front locker is all for more trails in Moab.

I've done 90% of the level 4 and below trails, time to explore the 5-7's.

Put it on, and get one for the front. If you’re progressing to more difficult trails in Moab and other areas, you’ll use it.

 

[Jaxmax]

Don’t do the diff covers the New Venture Skid , takes your protection to a much higher level your also protect the yoke. Send the diff covers back and get both skids. I have Dana cast diff covers and they will work for me but take it from a guy who is a poser but has a friend named Dan in Colorado, those expensive skids are the way to go……Jack

 

[WILDHOBO]

Don’t do the diff covers the New Venture Skid , takes your protection to a much higher level your also protect the yoke. Send the diff covers back and get both skids. I have Dana cast diff covers and they will work for me but take it from a guy who is a poser but has a friend named Dan in Colorado, those expensive skids are the way to go……Jack

I truly don’t have a single scratch on my factory covers. They don’t get touched.

 

[hjdca]

Note: My Metalcloak setup has been dragged over many, many rocks including the 3 badge of Honor Big Bear trails multiple times and the Rubicon Trail and has been really bullet proof. Here are some older picks, the skids are much more marked up now.

Front

Rear

2 color powder coating:

 

[WILDHOBO]

Note: My Metalcloak setup has been dragged over many, many rocks including the 3 badge of Honor Big Bear trails multiple times and the Rubicon Trail and has been really bullet proof. Here are some older picks, the skids are much more marked up now.

Front

Rear

2 color powder coating:

Metalcloak makes very nice stuff, and I have some of it, but I’d prefer a skid that protects the entire diff housing and pinion.

Sponsored