Rear axle fluid

[Huntinwild88]

Bought my 21 JLUR 12 days ago. Was able to pull it into the shop to do a oil change and checked all fluid levels.
I noticed some oil around the rear axle breather tube and wanted to check the fluid level. As soon as I pulled plug oil stared pouring out! So quickly shoved that back in.
Is there any reason it would be Over filled and how? Front axle was just below the fill hole.

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[jludave]

Is there any reason it would be Over filled and how?

Gear oil was previously changed by someone else and it was overfilled.

 

[Old Jeeper]

There is a reason why the fill hole is where it is.

Here is what us rock crawlers do: Size to fit street elbox and threaded pug.

Moab and many other can be hard on rear axles, especially on very steep trails, usually the 7++ stuff.

What happens is the long vertical trail the oil all goes to the rear pumpkin. So the nose does not get much oil and a week-long gig in Moab can lead to burnt pinion bearings.

 

[Heimkehr]

I noticed some oil around the rear axle breather tube and wanted to check the fluid level. As soon as I pulled plug oil stared pouring out! So quickly shoved that back in.

You might consider removing the fill plug again, so as to allow the existing gear oil to self-adjust to the correct level. Or, drain and refill to the proper specification. Doing the latter will allow you to establish a base service date, so to speak, for future reference.

 

[JAF1]

There is a reason why the fill hole is where it is.

Here is what us rock crawlers do: Size to fit street elbox and threaded pug.

Moab and many other can be hard on rear axles, especially on very steep trails, usually the 7++ stuff.

What happens is the long vertical trail the oil all goes to the rear pumpkin. So the nose does not get much oil and a week-long gig in Moab can lead to burnt pinion bearings.

What does the street elbow do? Allow you to fill it to a higher level just for off road?

 

[Huntinwild88]

You might consider removing the fill plug again, so as to allow the existing gear oil to self-adjust to the correct level. Or, drain and refill to the proper specification. Doing the latter will allow you to establish a base service date, so to speak, for future reference.

That was my original thought and I'll do it in the next day or two.
I'm going to be throwing 4:88's in it soon enough hopefully in the next month. I just don't understand how you over fill it!

 

[Huntinwild88]

Makes for easier top off when some leaks out the breather from being at such extream inclines is my guess.

 

[CarbonSteel]

Makes for easier top off when some leaks out the breather from being at such extream inclines is my guess.

Until you drop off from a rock shelf and hit it...

 

[Geronimo]

How it might happen is when it was drained for service and was not drained completely. Then a high school kid at dealer was told that the unit requires XXX amount of fluid. Then said youngun was determined to stuff it in there like a good employee, subsequently squirted it in there then stuffed the plug in before it could escape.

(You just repeated the 2nd part of that process) Now it is still overfilled.

I would drain, pull the cover, inspect for trash, chips and signs of strange gear wear, admire your locker.... Seal it back up and fill with new fluid of your choice to bottom of fill hole.

Then you will know its right, and can log it in your new little maintenance book and life will be good.

 

[Old Jeeper]

What does the street elbow do? Allow you to fill it to a higher level just for off road?

Yes, but there is no NEED to drain any oil if you are wheeling regularly. Its all done on 'splash' inside the axle. So a 3 in lift does what to the pinion angle? Now you are going up some very steep rocks in Moab or Table Mesa in AZ tdd and that splash does not reach the pinion bearing...

 

[JAF1]

Yes, but there is no NEED to drain any oil if you are wheeling regularly. Its all done on 'splash' inside the axle. So a 3 in lift does what to the pinion angle? Now you are going up some very steep rocks in Moab or Table Mesa in AZ tdd and that splash does not reach the pinion bearing...

Got it! I guess you could always just jack up the rear diff while filling it and still use the same fill plug to allow you to add more oil without the need for the elbow. I would be worried about something hitting it.
Thanks

 

[Gorilla57]

You don’t need to overfill your diffs to tackle high angle climbs. You aren’t doing high speeds at that point and the residual amount of oil on the pinion bearing will suffice until you level off and gain enough speed to splash fluid back onto the bearing. Plus, the little bit you overfill it won’t be enough to keep the pinion covered up, the diff would have to be completely full to do that. This is the stuff we climb and no one has ever had a bearing failure.

 

[CarbonSteel]

Yes, but there is no NEED to drain any oil if you are wheeling regularly. Its all done on 'splash' inside the axle. So a 3 in lift does what to the pinion angle? Now you are going up some very steep rocks in Moab or Table Mesa in AZ tdd and that splash does not reach the pinion bearing...

Could you ever get on an angle steep enough and long enough while moving fast enough to prevent the rear pinion from receiving lubrication long enough to fail without losing the Jeep itself?

Color me skeptical. Even though the lubrication is "splash" in nature, the ring gear will still move the lubricant to the pinion, and it carries oil itself within its teeth in addition to the splash it creates. As long as the ring gear is not starved for oil which it would not be in the rear axle on an upwards incline, it would be fine.

Even the front would not be a concern on a steep angle because the pinion would be partially/mostly submerged in oil and lubrication would be still be adequate.

 

[Maverick909]

Something no one said..... might be worth while pulling checking for water..... water in the diff will raise the oil level. I'd take it for a 10-15 min drive then pull the fill plug and check for milky oil. if the oil isn't milky then just drain it until it just comes out of the fill plug and seal it up. but with the oil coming from the vent tube that is a possibility of water being able to get in as well.

 

[Old Jeeper]

Could you ever get on an angle steep enough and long enough while moving fast enough to prevent the rear pinion from receiving lubrication long enough to fail without losing the Jeep itself?

Color me skeptical. Even though the lubrication is "splash" in nature, the ring gear will still move the lubricant to the pinion, and it carries oil itself within its teeth in addition to the splash it creates. As long as the ring gear is not starved for oil which it would not be in the rear axle on an upwards incline, it would be fine.

Even the front would not be a concern on a steep angle because the pinion would be partially/mostly submerged in oil and lubrication would be still be adequate.

Possibly, there is some VERY steep stuff in Moab and other places I have wheels. But NOT likely to initiate a failure on a steep slope its more of an accumulation of wear over time. Remember the D 44 was not a Hi Pinion axle set, I sold not to long after than. At this stage of my life, I had sold my company and sole mission was wheeling.

The reason I did this was that I knew some folks in the Jeep group who had burnt out their pinion bearings on the OEM D 44. Since I had a set of Pro Rocks on order I sure did not want my OEMs in need of repair as they were up for sale.

We talk about splash. Rock crawling is NOT a high speed sport so the splash often does not make a BIG splash when driving at walking speed.

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