I posted a few weeks ago regarding some problems I've had with front differentials in my 98 D. Got some good advice, have my shifting procedure down, all should be well, right?

Well, not so much. I was checking my antifreeze yesterday and noticed that the front diff is blowing gear lube out through the breather tube right next to the radiator cap. With a fairly large amount of lube all over the engine compartment and only about 200 miles on this new differential, I'm obviously a bit concerned.

Is this a known issue with an easy fix? Or even a not so easy fix? Or was it maybe overfilled and this will settle down and I can just not worry about it? Checking and topping up differential fluid on a weekly basis sounds like a giant pain in the butt, especially when it's 3 degrees outside...

 

Most likey you have too much fluid in the diff or the incorrect lubricant/contaminated lubricant.


Let it sit over night on flat ground. Take the fill plug out of the front diff and see if the lubricant flows out. The lubricant should only be just at the bottom of the hole or just below the hole maybe a 1/2 inch. If any flows out just let the overage aleviate it's self.

If the fluid is below the fill plug and everything looks good then replace the lubricant with Mobil One 75W-90 Fully Synthetic LS Gear Lubricant.


Take pictures if you are not sure.

 

Sounds easy enough. I was definitely ready for some good news on this thing (water pump crapped out 2 days after I got it back from having the differential replaced, then against my better judgement I put some stop leak in the radiator hoping to slow the leak enough to wait a few weeks before putting more money into it. You guessed it, now I have no heat. I freakin' know better than to use that stuff, but still catching up on bills after being out of work for awhile so trying to save pennies wherever I can, and this one bit me in the ***...).

I'm assuming that same lube is cool to use in the rear diff as well? It's due to be checked as well.....

 

Yes,

However if you have a Limited Slip rear differential then you also need to first place a 7oz bottle of friction modifier in it.

To find out if you have a LS dif, place a jack under the differential and raise both rear tires off the ground. Turn one wheel and look at the other. If the other wheel turns the same way as yours then you have a LS diff and need the friction modifier, if it turns the opposite way then it's a Open Gearing rear diff and that does not require the friction modifier.

You can get the friction modifier at Auto Zone for $4.99 for a 7oz bottle. Place the entire bottle in then top it off with the gear lube if it is indeed a LS diff.


Sorry to hear about the water pump. Back flush the heater core with a garden hose.

 

Had the mechanic who was doing my water pump flush it. Given my track record with Murphy's Law I was skittish about running plain water through it with the temps we're having. Any unexpected problems during reassembly and it would have had plenty of time to freeze while I made the trip to the parts store...

But HOLY CRAP!!! The thing has always had good heat, but now it's unbelievable. Yesterday on the way to work it was 10 degrees outside, I had the blower on the low setting, and I still had to crack a window for awhile to cool it down inside a bit.

Sure beats freezing my but off for the entire drive!