Ok, on the Rattlesnake Canyon Memorial Day run, I got hung up on my rear diff and since then it was leaking a little bit. I pulled the cover, cleaned things up, put the cover back on, and filled with fluid. Everything looked fine and no problem.

So, I go for a drive of approximately 20 miles. About 15 minutes after getting home, I see a puddle under the XJ. I check and it's gear oil. Upon closer inspection I find that it appears to be coming from the top of the vent tube on the driver's side. 2001 XJ with Dana35. The brake line comes from the front and makes a T on the driver's side axle tube. Off the top of this junction is a rubber tube which I think is the axle vent? Anyway, the puddle on the driveway was at least 1/4 quart, and from the splatter/leakage signs up at the top of the tube, I'd say I lost at least 1/2 a quart while driving around.

What did I do wrong?
What's causing this?
Do I just pull the fill plug and top it back off?
??????

From dirt accumulation around where the oil is coming out, it looks like it has done this recently. (Before I changed fluids this last week.) Also, I put my hand on the diff cover and axle tube. Both were quite warm. Not so hot I couldn't hold my hand there, but warmer than I thought they should be. ???

Would pictures help?

I didn't overfill it either. If anything, it's underfilled. I needed to buy another quart of oil and top it off anyway since I didn't have enough to fill it up.

blah this reminds me that I need to get a vent tube :eyeroll:

Virgil, what kind of diff cover do you have? Only reason it will leak from the vent tube is if it's too full. If you have an aftermarket diff cover that moves the fill plug up then odds are it is over full.

A negative pressure could do it (ask the yellowsub) but I doubt you've extended yours inside like theirs was.

Skatchkins wrote:A negative pressure could do it (ask the yellowsub) but I doubt you've extended yours inside like theirs was.

I was told this by another person and think it may be what's happening. He said he had a similar problem with his ARB locker pressurizing the axle and pushing fluid out the diff. Basically I'm maybe getting more pressure inside the axle and it's pushing fluid out starting a siphon action that is sucking the rest of the fluid out. He suggested taking the vent line off and making sure it is clear of blockages and even using the air compressor on a lower pressure to blow/push the fluid back into the diff clearing out the vent.

Well, I had the stock diff cover with a half guard that bolts on top of it. I added a SOLID full diff cover when doing the change. The fill plug does sit a little higher, but I'm sure I didn't overfill as I only had about 1.5 quarts to start with. Even without this problem I still needed to add more oil.

Thanks for the suggestions.

How hot should the rear axle get? I'll clean things up and check fluid levels tonight, but I wanted to make sure I'm not running it dry and blowing things up.

K7AZV wrote:How hot should the rear axle get? I'll clean things up and check fluid levels tonight, but I wanted to make sure I'm not running it dry and blowing things up.

If it's too hot for you to hold your hand solidly on it for several seconds without feeling a burn then it's too hot.

What if I can hold my hand on it for a long time, but it burns my flesh and turns black and starts smoking?

Thanks for the help guys.

Well, I made sure the vent line was cleared out tonight. Added a little oil and then drove about 10 miles. Stopped and filled it up for gas and it's still spewing oil out the top of the vent line. Well, maybe if I run it dry, it will blow up and then I can get a real rear axle.

I'm sure I'm not overfilling this. Anyone have any other ideas why it's pushing oil out the vent line still?

Well, it's still leaving puddles under my Jeep.

Rear axle capacity is listed as 3.6 pints.
3.6 US pints = 1.8 US quarts

I didn't fill it with more than that. I'm towing my camper up to Payson this weekend, so we'll find out if the diff is dry or not.

Well, I stuck a piece of wire down the fill hole using it as a dip stick to check the oil level. It's about half way up on the axle tubes, so it's not running dry. When I did the change, I added back less than 2 quarts, not filling it up to the hole. I still don't get it, but it gives me a little piece of mind that I'm not going to be towing the camper on a dry axle this weekend.

I can't believe how much fluid it has spewed out the top. I was sure that thing didn't have any left. Cost me $3 at the car wash on the Soapy setting to clean off the mess it made.

if you have time can you take a pic of exactly where you think its coming from?

Vent line on the drivers side. (Top of the vent line I should add.) All symptoms lead to it being overfilled, but as I've said many times, I disagree.

I'm shopping for a new axle to replace the D35. Looking for a XJ 8.25 or D44. I think it's time to swap axles, regear, and be done with it.

Virgil, if there's fluid half way up the tube then it's way too full. What happens when there's that much fluid in there the shafts spinning causes the oil to be slung up and then subsequently out the vent tube. Your best bet is going to be draining the whole thing and re-filling it with exactly what the 35 calls for.

Ok, stupid question. When I pull the diff cover off, does that also drain the axle tubes? Doesn't filling the diff let oil into the axle tubes? Maybe I didn't drain it fully?

K7AZV wrote:Vent line on the drivers side. (Top of the vent line I should add.) All symptoms lead to it being overfilled, but as I've said many times, I disagree.

I'm shopping for a new axle to replace the D35. Looking for a XJ 8.25 or D44. I think it's time to swap axles, regear, and be done with it.

DUDE! I know where you can get a D60!

Haha, he already PMd me.

K7AZV wrote:Ok, stupid question. When I pull the diff cover off, does that also drain the axle tubes? Doesn't filling the diff let oil into the axle tubes? Maybe I didn't drain it fully?

Yeah when you pull the diff cover off it will drain all but the most minute level of fluid out of the tubes. It just seems like if your dipstick was showing there was fluid half way up the tubes then there is too much. There is always going to be some fluid in there, however in your case if it's touching the shafts then it's being slung all over the place in there and hence out the vent tube. Like you showed earlier. You want no more than 1.5 quarts in there no matter what diff cover you have.

Thanks guys. I overfilled it. I don't understand how, but I overfilled it. I should know more after this weekend to see how pulling the camper does and if it leaks more.