I spent a couple hours doing some work on my 91 yj this weekend. I replaced the gear oil and gaskets on both my front (D30) and rear (D35) axles. While I had the covers off, I noticed a couple of things that were worth remembering to ask on here.

First, on the D30, there are two threaded holes, one on each side, that aren't used and the cover doesn't have the holes. Was this a previous design that they just got cheap and stopped using the bolt holes?

next... The front has never had it's cover off, but the oil seemed to be in really good shape! Good thing! I did notice that there is a little slack on the short side's shaft. Not enough to "see", but I could feel a little play, more like hear... It's around the bearing right there in the diff. Is this normal or something to be worried about?

next... The front axle had no metalic residue in it whatsoever. Another good thing, and no chips or anything either. The outer edges of the spider gears seemed a little rough, but seemed to have been like that for a really long time - perhaps from the factory? They don't bind or hang or anything, just don't look right. Am I over-worried about them?

next... how much fluid hides up in the tubes? Specs indicate that I should have put 2.5 quarts in each dif., but I barely put in 2 before it started flowing out. I drove around the block a couple of times and let it set and checked, full, up to the bottom of the fill hole, so, still wondering what the capacity should be.

Next... "if it ain't broke, don't fix it" aside... how often should one replace the gear oil in the diffs? same note, how often should one change the fluid in the x-fer case?

lastly. the rear D35 oil was grayish and there was a little sludge in the bottom, no chips and nothing severly magnetic. How many miles of moderate to hard driving should the oil go through before it starts looking like what? This is a Jasper rebuild from 1998 and has over 100,000 miles on it....

Overall, this was a messy, but fun weekend. Just left me with a couple of questions....