hyperbolical

So ... I am preparing to change my differential fluid but as a prelude as I wait for the supplies, I popped the plug off today and dipped my finger in the hole to see what the fluid was like and how low it was.
It was about 1" below fill line. It may be another week before I can get my lubelocker and other supplies to change it out. Do I need to run and get some oil to top it up right away or is it ok for a week? Since there's no dipstick, I only know that the level should go up to the plug. Is this bad, urgent, or somewhat normal?
The fluid was dark and had a few glitters in it but not many. I saw maybe 4 or 5 in this small sample I siphoned out, about a tablespoon of fluid. Here is a pic. I have no idea if this is normal, can someone comment?
What I found in my records was that my rear seals had been leaking on my rear brakes and in 2020 my mechanic replaced the seals and brake shoes. Would he have had to pull the axles and drain/replace the fluid in the differential to do that? If he did, then he may not have put the friction modifier in. He didn't mention draining the differential at the time.


Thank you, I have learned so much from you all and appreciate your help.

Sirsyc0

Gear oil doesn’t just get low. Either it wasn’t topped up when the axle seals were done or you have a leak. 1” below the fill hole is a considerable amount of oil and you would see the leak. Some fine particles in the gear oil is normal. Just my opinion, but I wouldn’t run an axle that low.

hyperbolical

Thank you, I don't see a leak around the differential, but where else might I look? Presumably the wheels. anywhere else?

SirCyber

If it were mine, I'd top it off and just monitor it. If you haven't checked it since the seal job, it's quite possible it didn't get filled all the way. To do the axle seals you would have had to drain the diff, so it's possible that it was just never filled all the way. once you do your gasket job, check it again after first drive, a week, and a month after just to make sure you don't have any creeping issues

Sirsyc0

Leak points are pinion seal, diff cover and axle seals.
Yes. Look at wheels from the inside underneath. Axle seals would leak on the the backing plates, the brake drum and the inside of the rim.
Pinion seal where your drive shaft connects. Pinion seals can drip off the diff housing and/or sling oil with the spinning of the drive shaft.

lawsoncl

I wouldn't panic and stop driving it. There's still plenty of oil in there even at 1" below the fill plug. That rubber fill plug tends to leak as well.

robsjeep

Sure, wait a week, just dont drive it much.

Add a drain plug with a magnet. heck I added a drain and got a magnet on both plugs.

hyperbolical

Thanks everyone. I guess I'll wait on topping it up since it's only a few days. And I've probably been driving it a few years like this. I wonder if this low level could be related to the groaning and moaning I hear sometimes when I take off from a stop and am making a turn? I looked in the FSM and it says, change the fluid before making any repairs on the Trac-Lok diff, because the level and condition and type of fluid could be related to noise from there. I certainly hope that is all it is. Looking at the pages and the possibility it is a worn bearing, I think what is different about my noise from pinion and diff bearing noise is that it goes away as I pick up speed, whereas the service manual says it would pick up if either of those. Also the pitch. Pinion noise is high, diff bearing is low. so that rules out pinion. Mine is low. Axle shaft noise- since my noise goes away as I pick up speed and its only when I turn, that seems the most probable, if the noise is not coming from within the diff itself. I would have thought my mechanic would have checked those bearings when he did the seals, though. But that in fact would be far better than a diff repair or replacement, wouldn't it? What happens if I drive on bad axle bearings for awhile? Does anything else get damaged?

BwanaBob

If the differential oil level is low and you are hearing noises like you describe,
you really should open it up, drain it, and pull the axle shafts to inspect them.
A bad bearing can wear a groove in the axle shaft, which would then need to
be replaced. Aftermarket shafts cost $100 to $200 each.

If the shaft looks smooth where the bearing rides, I would replace the bearing
anyway and the seal. You'll be good for years.

hyperbolical

ok thank you for this info!! ... in my notes the mechanic said he had examined the shafts when he did the seals and brake shoes and they were 'good for now', that he had been afraid they were ruined like the brake shoes- that was in 2020. That was exactly 3 years ago and due to Covid I didn't drive much until last fall. It's my daily driver not something I take on the trail. I began hearing the low growling when turning from a stop sign maybe this January. But he didn't explicitly say he replaced the bearings, that I can remember. He has an excellent reputation in the area and I can't imagine he would not have examined the bearings or replaced them at the same time. I do not currently see any leaks around the wheels, pinion, or diff case. I'm just taking a guess that it is wheel bearings due to sound description, and I'm new at this. But it just seems like they shouldn't be the cause since he did all that work not that long ago. What else could this noise be from? Any ideas?

dzywicki

Since you are going to change it out anyway, I would top it up, drive it and monitor the level to find out if you do have a leak since it is so easy to check the level. I use an oil suction gun like to fill my diffs. Better to know you don't have a leak before you do the full job and then find out you do have a leak. I also use an oil suction to suck all the fluid out so I don't have to mess with removing the diff cover and dealign with all that mess. I also have 4 jeeps so saving time on jobs like this is really helpful to me so I can do them all in the same amount of time as one if I had to remove all the diff covers etc. Good luck.

hyperbolical

Great idea! I will do it!
for some reason the links you posted don't work for me, can you please tell me the names of the items so I can look them up? thank you!