Huklbery

I drained both diffs for the first time today on the level floor of my garage, and both drained from the filler holes before I even got to removing the drain bolts. I checked the quantity of fluid from each axle against the specs for Dana 44 front and rear axle capacities, and they were very close.

That suggests to me that both axles were overfilled at the factory; an idea that is supported by the fact that neither axle accepted that same amount of gear lube before weeping it back out the filler hole when I refilled them. I drove around for a bit and tried topping the axles off again, and they took a few ounces more, but not as much in total as had been in them before they were drained. (I'd say each is about a quarter to a third of a quart light, compared to the capacities reported in this forum, which is also how they came from the factory.)

So, if the capacities shown on this forum are correct, how do you get more oil into the axles than the height of the fill holes on the stock diff covers allow? Through the breather hoses?

RedneckJeep

I don't worry about filling to the bottom of the fill hole. That's not a very accurate measurement at all. I just put in the recommended amount in the owner's manual. Works for me.

ronjenx

Earlier in this thread, I outlined how much came out of my diffs.
The front had adout the published quantity, which was 15oz more than the fill hole will allow. I put the front on ramps to tip the diff back some. This allowed more fluid to be poured in.
See post #3.

Huklbery

Unless I'm missing something (very possible), my owner's manual doesn't list capacities for the differentials. The only place I've seen quantities listed is here, on this forum.

In fact, the owner's manual doesn't specify a mileage at which the diff oil must be changed. All it says is to inspect it at 18,000 miles.

Huklbery

If you're correct (and I have no reason to think you're not correct) that it's necessary to tilt the vehicle in order to fill the diffs to the correct level:

(a) it's impossible to check the fluid level in the diffs unless the vehicle is tilted at the same angle

(b) it's impossible to change the diff fluid on a lift -- say, at a dealership. Does anybody know how Jeep dealers are instructed to refill the diffs?

(c) why didn't they simply position the fill holes in the factory diff covers an inch or so higher?

The detailed instructions ("Jeep JK Wrangler Maintenance Differential Fluid Change Write-Up") for changing diff fluid I downloaded from Project-JK.com say nothing about the need to tilt the vehicle. There are questions from two JK owners following the write-up expressing concern about their inability to get more than a quart in the front and two quarts in the rear diff, followed by reassuring replies saying those are the correct amounts, even though they disagree with the quantities specified in the write-up itself. But that might be a case of the blind leading the blind.

There's a lot of very useful information on this forum, and I've gotten a lot of great ideas here. There are also some urban legends floating around. It would be helpful to hear from someone who's familiar with the instructions that are given to Jeep dealerships about changing the diff fluid.

TEEJ

Typically, parts with multiple levels internally, like trannys, diffs which are connected to axle tubes, etc...will NOT drain completely, and, will therefore require LESS lube to RE-Fill them, as some of the volume is already present.

Think of it this way; the diff is a "Fat Part of the Axle TUBE".



That means you can be on level ground, and some oil will be pooled in the REST of the tube, and NOT drain out.

It will typically NOT be in the breather, as that is at a HIGH point.

I noticed that at least ONE poster above DOES tip the axle first one side, and then the other, TO run that tube trapped oil into the diff again for draining....and, that is ALSO what I recommend for better efficiency.

Its NORMAL to not get all the lube out, on trannies for example, you are LUCKY to get 1/3 of the old lube out....2/3 is still in there if you just drain it w/o a flush, etc...

Do NOT expect to drain the volume of oil it says you need to FILL a diff...as the tubes, etc...have part of it trapped even with tipping, etc.

Hope that helps!

Huklbery

I appreciate your help, thanks, but my question was originally prompted by the fact that I wasn't able to replace the same volume of oil that drained out. In other words, I had no problems draining the oil -- it's getting the diffs to accept the same quantity on refill that had me questioning the write-up on Project-JK and the correct quantities.

ronjenx

Huklbery,

My front diff had about the correct quantity of oil in it. That quantity was 15oz above the fill hole. I put the front end up on ramps so I could put the correct quantity back in. I decided to do this because it is a high pinion axle and I wanted to make sure the pinion bearings get some of the oil on them. I have no leaks or blowing overboard. So, I am happy with my decision. Also, some people have posted about their diff getting hot in the pinion area of the housing. Mine stays about the same temp as the rest of the diff housing.

rubiconjack

are there any gaskets that reed replaced when swapping diff oil out.

I haven't done it yet, and should .. there isn't any special mixture need for the lockers to is there????