Overfilled rear differential... axle seal leaking

[Flex BT]

I drained and filled the rear differential fluid on my new-to-me CJ7 a few days ago. I didn't take into account that the differential is tilted up at an angle and filled it up to the plug. I drove it a few miles and parkedit without issue. The next day my wife called me from work and said it was leaking all over the driveway. It let a good amount of clean diff. fluid on my driveway. My question is, is it possible that the seal just had fluid move past it or is it definitely blown and needs to be replaced? Is the best way to check the vent to remove it from the axle and try to run water through it?

 

[Torxhead]

Interesting how a seal would go bad after a fluid change. An axle vent can be checked for obstructions by removing the fill cap and blowing thru the top end of the vent.

 

[NorthwestCJer]

How much oil did you get out of it? before putting new back in!
You say the jeep is new to you. The previouse owner may have lowered the fluid level so you wouldn't notice the seal leak.

 

[coldair]

I'm with torxhead check your vent on the axle.

 

[Old Dog]

the seal needs to be changed. The pinion tilted up would not make a differance, if anything it would make it a little low not over filled.

 

[Kane]

the seal needs to be changed. The pinion tilted up would not make a differance, if anything it would make it a little low not over filled.

This statement is incorrect and I had the same problem. I tilted up my model 20 dif to match the CV driveshaft I bought. When I did that the fill plug which is located right next to the pinion turned up higher. This will increase the fill height and allow the oil to bascially fill the axle tube cavity before you get to the proper fill height at the hole. Mine leaked like crazy. I drain enough oil out to get it below the axle tube height and the problem never came back.

 

[Old Dog]

sorry about that, I was thinking of a dana with the fill plug in the cover.

 

[Flex BT]

I drain enough oil out to get it below the axle tube height and the problem never came back.

That's a relief to hear, it hopefully will be the same with mine.

A good amount of oil came out of the diff when I drained it so it didn't seem like I got set up by the PO. After I check the vent hose and oil level I'll go out for a little drive and see if the jeep is still creating an environmental hazard.

 

[mtnwhlr]

This statement is incorrect and I had the same problem. I tilted up my model 20 dif to match the CV driveshaft I bought. When I did that the fill plug which is located right next to the pinion turned up higher. This will increase the fill height and allow the oil to bascially fill the axle tube cavity before you get to the proper fill height at the hole. Mine leaked like crazy. I drain enough oil out to get it below the axle tube height and the problem never came back.

x2 I think it is fine

 

[jasonmark1993]

I wouldn't recommend having your oil level below the axle tube; you'll starve the axle bearings.

As far as the seal starting to leak after the fluid change, I don't know.

If having oil in the axle tubes is the problem, you'll leak every time you are on a side hill or go around a corner.

 

[Flex BT]

If I do get new axles are the superior narrow ones the way to go for my 81' CJ7 ? When I take the wheel off I've got a dust cover, that means I have the two-piece version, right? Can anyone point me to a good step-by-step for changing to one piece axles?

I also looked for an AMC20 rear diff. cover with a fill / drain plug and didn't find one. Does it exist?

 

[BusaDave9]

I agree with jasonmark1993 the seals should be able to seal oil that is at a level above the seal. I think the seals are bad but it could also be a clogged vent. If you go to one piece axles you will get new seals. To tell if you have the OEM 2 piece axles look at the rear hubs. If there is a big nut in the middle of the wheel you have 2 piece axles.

The above axle is 2 piece.

 

[Flex BT]

How does that dust cover come off that goes over that area, is it threaded or do I just need to pull hard enough?

I disconnected my vent hose yesterday and blew into it. It had resistance for a second then blew through without a problem so I probably just dislodged a big hunk of into my differential case

 

[Old Dog]

If I do get new axles are the superior narrow ones the way to go for my 81' CJ7 ? Can anyone point me to a good step-by-step for changing to one piece axles?

I also looked for an AMC20 rear diff. cover with a fill / drain plug and didn't find one. Does it exist?

I would measure the WMS to WMS to be sure. You never know what someone has done. NT is 50", WT is 54.5".

Superior has downloadable instructions on there web site.

I don't know of any covers with plugs either. But you could add some the the covers like BTF makes.

 

[mtnwhlr]

How does that dust cover come off that goes over that area, is it threaded or do I just need to pull hard enough?

It just pushes on sometimes you have to pry it off.

 

[jasonmark1993]

i wouldnt worry too much about that piece of crud that you blew into the diff.

i might have missed it but are the axle seals leaking or the pinion?

if it were mine and i didnt have a long trip planned id drive it and see if the cleared vent helps.

Your new oil will be a little thinner so maybe the seals were already waiting to go.

Sneaking in some upgrades while doing a $5 seal is awesome. I'd put a 9" or a 60 in there

I don't know how much your axles cost but maybe you could get a used 44 for a couple hundred bucks.