Differential Fluid Questions [Archive] - JKowners.com : Jeep Wrangler JK Forum

: Differential Fluid Questions


jkdrone
07-06-2008, 12:54 PM
So, at 7500 miles, went ahead and swapped out the oil, and the diff fluid. I like Royal purple, and used it in all of my previous vehicles, so I'm keeping with that tactic on the JK.

A few questions though:

(I have dana 35 front, d44 + LSD rear, 3.73 gearing)

1) My front diff fluid was a light tan, milky color with lots of little metal bits in it.
-> I presume the milky color means I got water in it? am I right here?
-> I presuming the little metal bits are from the gears being new and this being the first fluid change on the front diff? I pulled off about half an inch of metallic goo from the magnetized drain cap. Should I drain it again soon and see if I still get lots of metal?

2) The rear diff fluid was black, blacker than night. I'd guess this is because it gets a lot more wear from being always powered? It was a lot blacker than I had expected - think dino engine oil that's been run for 10k miles! I think it had plenty of metal in it, but couldn't really tell, it was pretty black. Not nearly as much material on the magnet as on the front.

3) I put 75-140 (Royal Purple) in both diffs - I know the manual recommends 75-90, unless doing heavy towing. I had a bunch of 75-140 left over from the commander, so I used that. Any known issues?

And, finally, a comment. It runs a LOT smoother now! Drove about 35 miles after swapping everything out, and it really seems to take off smoother. I wasn't getting "chatter" before, but I could feel something rough in the drivetrain when accelerating, and now I don't feel it. No chatter going around corners, so I'm presuming I don't need to add any LSD modifier.

!c

YmansJK
07-08-2008, 10:23 AM
So, at 7500 miles, went ahead and swapped out the oil, and the diff fluid. I like Royal purple, and used it in all of my previous vehicles, so I'm keeping with that tactic on the JK.

A few questions though:

(I have dana 35 front, d44 + LSD rear, 3.73 gearing)

1) My front diff fluid was a light tan, milky color with lots of little metal bits in it.
-> I presume the milky color means I got water in it? am I right here?
-> I presuming the little metal bits are from the gears being new and this being the first fluid change on the front diff? I pulled off about half an inch of metallic goo from the magnetized drain cap. Should I drain it again soon and see if I still get lots of metal?

2) The rear diff fluid was black, blacker than night. I'd guess this is because it gets a lot more wear from being always powered? It was a lot blacker than I had expected - think dino engine oil that's been run for 10k miles! I think it had plenty of metal in it, but couldn't really tell, it was pretty black. Not nearly as much material on the magnet as on the front.

3) I put 75-140 (Royal Purple) in both diffs - I know the manual recommends 75-90, unless doing heavy towing. I had a bunch of 75-140 left over from the commander, so I used that. Any known issues?

And, finally, a comment. It runs a LOT smoother now! Drove about 35 miles after swapping everything out, and it really seems to take off smoother. I wasn't getting "chatter" before, but I could feel something rough in the drivetrain when accelerating, and now I don't feel it. No chatter going around corners, so I'm presuming I don't need to add any LSD modifier.

!c

Ok first off you should have a 30 front and 44rear.
Milky oil means water in the oil
As for the metal shavings, if they persist then you should get it checked out. As for the oil being black that is normal.
75-140 should be fine. This is what they recommend for TJ's and the book calls for 80-90. Also do you need to add a additive in the rear for the LSD or not? Your manual should say so.
Hope this helps

jkdrone
07-08-2008, 10:30 AM
Ok first off you should have a 30 front and 44rear.
Milky oil means water in the oil
As for the metal shavings, if they persist then you should get it checked out. As for the oil being black that is normal.
75-140 should be fine. This is what they recommend for TJ's and the book calls for 80-90. Also do you need to add a additive in the rear for the LSD or not? Your manual should say so.
Hope this helps

Yes, you are correct, it is the D30, not D35 up-front.

Ok, good to know about the black, and I'll drain the front again in 30 days and see if I continue to have lots of metal in there.

The rear requires additive due to the LSD, but the RP has it "already in there". Haven't had any chatter from the rear on corners, so I'm pretty sure whatever it has is "enough".

!c

PhilD
07-08-2008, 12:18 PM
As already stated milky fluid means you had water in the diff. You don't need to add any modifiers to RP.

Metal shavings are a sign that something is wearing. I've had them in the rear before, but never the front. If they are big, fingernail clipping size, that is usually not a good sign. Small ones are most probably okay, but I'd check the fluid often, (which can get expensive with RP).

I run Mobil 1 75W140 in the rear and it seems to stand up better to the heat, as the rear diff gets pretty hot.

I did run RP in both diffs, but it leaked passed the front axle seals quite a bit. So I switched to 80W90 dino in the front and M1 75W140 in the rear.

Dino oil tends to go black pretty fast in diffs, especially in the rear one. I've got 12k on the M1 in the rear and it is still nice and clean. The front tends to stay pretty clean anyway as it isn't do much work. Dino 80W90 was going black in a few thousand miles, in the rear.

If you are lifted you will want to add more fluid than stock as your pinions will be rotated up, and you want to make they get plenty of lubrication.

jkdrone
07-08-2008, 12:30 PM
Metal shavings are a sign that something is wearing. I've had them in the rear before, but never the front. If they are big, fingernail clipping size, that is usually not a good sign. Small ones are most probably okay, but I'd check the fluid often, (which can get expensive with RP).


Hmm, it was all "fine shavings" it looked like -- the fluid has an almost metallic sheen to it. Nothing big, but lots of little stuff.

I've still got 4QT of RP left, so I'm not sweating checking it a few more times for the next couple of months. If it has a bunch of metal next month, I'll pull the cover off and see if anything obvious is wrong. Wonder if they'd cover that under warranty.... :shaking:



I run Mobil 1 75W140 in the rear and it seems to stand up better to the heat, as the rear diff gets pretty hot.

I did run RP in both diffs, but it leaked passed the front axle seals quite a bit. So I switched to 80W90 dino in the front and M1 75W140 in the rear.

Dino oil tends to go black pretty fast in diffs, especially in the rear one. I've got 12k on the M1 in the rear and it is still nice and clean. The front tends to stay pretty clean anyway as it isn't do much work. Dino 80W90 was going black in a few thousand miles, in the rear.

If you are lifted you will want to add more fluid than stock as your pinions will be rotated up, and you want to make they get plenty of lubrication.

This has me wondering now, I have 2.5" of lift, and when I took the fill plugs out fluid came pouring out for a couple of minutes on the front (I presume from the added water), and for about a minute on the rear. I filled them up until fluid came out of the fill plug. I guess getting new diff covers is about the only logical answer to adding more fluid than that, heh.

I'll check the axle seals after this weekend's trip, and see if I get any leaking there. I noticed that my front diff seemed to weep a bit of fluid around the bolts at the bottom when wheeling (with stock fluid), not enough to get worried about, but I'll have to keep an eye out and see if the RP makes it worse. (It would appear darker around a few bolts, and wiping it revealed an oily substance, not like drops of it, just a light coating on the flange of the cover.)

!c

PhilD
07-08-2008, 12:42 PM
Hmm, it was all "fine shavings" it looked like -- the fluid has an almost metallic sheen to it. Nothing big, but lots of little stuff.That sounds fine, but it is unusual to find it the front, that's the kind of stuff you usually get in the rear.


This has me wondering now, I have 2.5" of lift, and when I took the fill plugs out fluid came pouring out for a couple of minutes on the front (I presume from the added water), and for about a minute on the rear. I filled them up until fluid came out of the fill plug. That's because the fill plugs are rotated down and effectively lower than when it was filled.


I guess getting new diff covers is about the only logical answer to adding more fluid than that, heh. Or add some through the breather vent. After seeing a stock cover just peel open on a rock, after market covers make sense anyway though.


(It would appear darker around a few bolts, and wiping it revealed an oily substance, not like drops of it, just a light coating on the flange of the cover.)May be worth checking the bolts, I've seen them loosen up a little from the diff been dragged over rocks. Also, if fluid can get out, water can get in.

jkdrone
07-08-2008, 01:55 PM
Thanks for the info Phil, I'll give a good checking over before hitting the road this weekend. New diff covers are definitely on the list, just down at priority #3 given the lack of rocks in my immediate area =)

!c

gcg
08-21-2008, 08:16 PM
Though it's sort of a "shade tree" technique for filling your diffs after a lift, you can also park your Jeep on an angle such that the pinion is close to level and fill it that way. I'm not really recommending this, and I agree that an aftermarket diff cover with a higher fill plug is the best answer, but it might help in the short term.