Your rear differential is rotated up - how much gear oil? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 17 Old 06-24-2010, 04:29 AM Thread Starter
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Your rear differential is rotated up - how much gear oil?

You bought adjustable control arms and now your rear pinion angle is correctly set, as in rotated upward so it points directly at the TC output. How much gear oil are you guys putting in your differential? I can't find a specific answer anywhere. I've read anywhere from an extra 1 to 2 quarts. Seems like too much to me...

My differential is rotated up by 15. I had to pop the cover last weekend. I refilled it with 2 full bottles of oil then added an additional 2.5 cups through the axle breather fitting. Will that be enough? I'm going wheeling this Saturday and my destination is over three hours highway drive away and I don't want to destroy my pinion bearing...

So any of you guys out there with upward tilted difs, how much oil? Thanks!


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Last edited by dkrz123; 06-26-2010 at 02:34 AM.
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post #2 of 17 Old 06-24-2010, 04:57 AM
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good question. on my tj i didnt put any extra in, what ever fit in there was what i used, its been going fine as a daily driver for over 3 years like that

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post #3 of 17 Old 06-24-2010, 06:40 AM
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Look in the owners manual for the correct quantity. IIRC it's less than 2 qts. Don't over fill it, but be sure you get the recommended fill quantity in there.
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post #4 of 17 Old 06-24-2010, 06:58 AM Thread Starter
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Originally Posted by SoK66 View Post
Look in the owners manual for the correct quantity. IIRC it's less than 2 qts. Don't over fill it, but be sure you get the recommended fill quantity in there.
I know what quantity is supposed be for unmodified JK's...
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post #5 of 17 Old 06-24-2010, 08:24 AM
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I've always used the regular quantity, in this case ~2.5 quarts. Park facing down on a steep hill to fill it, or get an aftermarket cover with a higher plug.

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post #6 of 17 Old 06-24-2010, 08:57 AM
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Originally Posted by dkrz123 View Post
I know what quantity is supposed be for unmodified JK's...
It's not any different if the stock axle has been modified with a locker, gears, etc. Same-same. If it's a D60, nine inch, etc., then go with the mfrs recommendation for that particular axle.
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post #7 of 17 Old 06-24-2010, 09:42 AM
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I have burned up the front pinion bearing in the rearend by only filling to the stock fill plug hole with 15 deg pinion, had to scrap the whole housing. I usually fill to the stock fill plug then unscrew the vent barb from the axle tube and squirt and extra qt in there. The factory capacity is 4.75 pts so I would add an extra 2 pts.

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post #8 of 17 Old 06-24-2010, 09:53 AM
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Park facing down on a steep hill to fill it
This is what I do for my rear. Park on a steep part of my driveway and fill to the hole.
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post #9 of 17 Old 06-24-2010, 12:04 PM
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I usually can just put jack stands under the tubes and get it close enough. The stock JK housings don't hold much oil so it's important to get the correct amount in there. Can't remember the vendor, might be Dynatrac, but one of them raises the fill plug on their reinforced diff covers.

Just checked the manual re: fill capacities.

Front D44 = 2.7 pints
Rear D44 = 4.75 pints

Front capacity is particularly skimpy, so beware, don't underfill.
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post #10 of 17 Old 06-24-2010, 12:12 PM
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pssst


Quote:
Originally Posted by dkrz123 View Post
My differential is rotated up by 15.

So any of you guys out there with upward tilted difs, how much oil? Thanks!


...
Quote:
Originally Posted by dkrz123 View Post
I know what quantity is supposed be for unmodified JK's...
Quote:
Originally Posted by GOAT1 View Post
I have burned up the front pinion bearing by only filling to the stock fill plug hole with 15 deg pinion, had to scrap the whole housing. I usually fill to the stock fill plug then unscrew the vent barb from the axle tube and squirt and extra qt in there. The factory capacity is 4.75 pts so I would add an extra 2 pts.

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post #11 of 17 Old 06-24-2010, 07:05 PM Thread Starter
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Quote:
Originally Posted by GOAT1 View Post
I have burned up the front pinion bearing by only filling to the stock fill plug hole with 15 deg pinion, had to scrap the whole housing. I usually fill to the stock fill plug then unscrew the vent barb from the axle tube and squirt and extra qt in there. The factory capacity is 4.75 pts so I would add an extra 2 pts.
This is the info I was looking for. Sorry about your pinion bearing but, thank you! I already have an extra pint in there now beyond the recommended 2.375 Quarts. I'll squeeze another 1 pint in down the breather fitting and I guess I should be good to go.

Is that breather fitting (vent barb) pretty easy to unscrew? I want to try that but I don't want to snap it off either. Will a vice grip work? Right now I'm using a rubber hose thing I made and attach one end to the bottle and the other to the fitting and squeeze. It works fairly well but it's a PITA and gets pretty messy...
Thanks!
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post #12 of 17 Old 06-24-2010, 11:04 PM
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pardon my ignorance but can someone post a pic of the breather tube. i had the problem of finding the capicity for my 08 rubi but the manual didn't list it or i could not find it in there. i called the dealership and they were vague about it. i have the river raider diff covers which are a bit bigger than stock. does that mean i need to add more oil due to the new covers? please help
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post #13 of 17 Old 06-25-2010, 04:35 AM Thread Starter
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Originally Posted by CARTER5150 View Post
pardon my ignorance but can someone post a pic of the breather tube. i had the problem of finding the capicity for my 08 rubi but the manual didn't list it or i could not find it in there. i called the dealership and they were vague about it. i have the river raider diff covers which are a bit bigger than stock. does that mean i need to add more oil due to the new covers? please help
The breather tube comes out of a fitting that is directly on top of the axle to the right of the differential.



Unless your pinion is rotated up to accommodate an after market drive shaft, you're probably fine with the 2.375 quarts that is supposed to go in there. Check with the manufacturer of the cover to be sure though. I'm no expert...

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Last edited by dkrz123; 06-26-2010 at 02:34 AM.
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post #14 of 17 Old 06-25-2010, 07:30 PM
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Quote:
Originally Posted by CARTER5150 View Post
pardon my ignorance but can someone post a pic of the breather tube. i had the problem of finding the capicity for my 08 rubi but the manual didn't list it or i could not find it in there. i called the dealership and they were vague about it. i have the river raider diff covers which are a bit bigger than stock. does that mean i need to add more oil due to the new covers? please help
Probably not. The fill quantities I noted above are in the repair manual, but as you found out, not in the owners manual. The latter includes lubricant specs only. Front is 2.7 pints (1.35 quarts) and rear is 4.75 pints (2.375 quarts).

FWIW, my JK Rubi UL (TF 4" lift) will short fill each differential by .7 pints if you just add oil via the fill plug in the cover. The front pinion is at basically stock angle, i.e., one degree, the rear is at about nine degrees. I add the remainder via the vents, or by raising the axle slightly.
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post #15 of 17 Old 06-26-2010, 08:20 PM
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Over filling the front dif

OK so the the front takes 1.35 quarts. I bought it in quart bottles so I added it in quart bottles! I drove up a steep little hill and added the rest of the second bottle. I also extended my breather by 2 ft and added a small fliter on the end of it. It sits next to my brake master cylinder now. On my 30 mile drive to work I blew gear oil all over the place. I agree with over filling it, just don't add 2 quarts to the front! Somewhere between 1.35 and 2 is enough! ha ha guess when it stops blowing out the breather I'll clean it all up and call it good. Next time I'll start with maybe 1.5 quarts and see how that does!!??
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post #16 of 17 Old 06-28-2010, 09:44 AM
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OK so the the front takes 1.35 quarts. I bought it in quart bottles so I added it in quart bottles! I drove up a steep little hill and added the rest of the second bottle. I also extended my breather by 2 ft and added a small fliter on the end of it. It sits next to my brake master cylinder now. On my 30 mile drive to work I blew gear oil all over the place. I agree with over filling it, just don't add 2 quarts to the front! Somewhere between 1.35 and 2 is enough! ha ha guess when it stops blowing out the breather I'll clean it all up and call it good. Next time I'll start with maybe 1.5 quarts and see how that does!!??
You dont need to overfill the front, you are not generally rotating the pinion up that much or any at all so there's no reason to overfill it. The axle seals are right at the differential so there is not much volume in the front diff so it will puke out the vent easier. Another thing, you don't want the oil level above the inner axle seals, if you ever pull the axles, the oil will dump into the tubes and that is a PITA to clean up.

The rear end has its seals out near the wheels so it has a lot more volume to it and not as likely to puke out the vent. The gear oil has to lubricate the wheel bearings also so the gear oil has to be at least past the bottom of the axle tubes.

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post #17 of 17 Old 06-28-2010, 09:17 PM
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