Ended up taking the Jimmy into the shop today where I plan on buying tires. Asked if they could check for what would be a problem when it comes time for the new tires/alignment. They put it up on the rack and checked the front end for free (now I gotta buy my tires there, LOL). Only thing they said needs replaced are both lower ball joints. Cool! So I have that lined up for this weekend, same guy who rebuilt my transmission a couple years ago, for a very reasonable price.

Also have a badly rusted rear differential cover on the list. This thing is pretty much seeping oil all over (neat pic if I can get it attached). Trying to figure out which rear end I have has been fun. No visible plate or stamping on the rear axle/differential. My codes only told me I have a G80 Positrac, 3.73 gear ratio. Finally found a post on here showing the covers and measurements, so I hope I ordered the right one.

So now I'm stuck on what gear oil to buy. I've seen some posts that say additive is required for limited slip (same as positrac right?) and other posts saying no additive required as long as I go with GL5 specs. I'm looking at the Mobil 1 Synthetic 75w90. Also saw the Royal Purple mentioned, but it's twice the cost, and seems to get the same reviews. Any opinion on which oil to use, and/or do I need an additive? Want to get everything bought in advance so there won't be any extra trips to the store after tearing this thing apart tomorrow! Thanks for all your help so far!

 

as far as dif lube i use lucas...always have...never any trouble with their products.
good thing you caught that...looks kinda ripe.

 

Ripe....good word for it. I'm a little surprised that nobody else caught it. Supposedly when I get oil changes, they check and lube everything. Just had an oil change a couple weeks ago and all they mentioned was the right front axle (which we've already discussed, and by the way, the alignment check guy never even mentioned my wierd hose clamps, LOL) and the backing plates on the rear wheels. My friend was looking under the car to see the backing plates, and he's the one that pointed out my rear diff problem.

I picked up the new cover this afternoon and ended up going with the Mobil 1 LS Synthetic 75W-90 for the lube. The cover came with a paper gasket which I'm planning to use. I read alot of people use black RTV, but that it's easier to use the gasket on vehicles like mine that have the rear sway (stabilizer?) bar so close to the differential. Keeping my fingers crossed that everything goes smoothly tomorrow.

 

Well after all that work....I was looking under my Jimmy to see the new ball joints that were installed this weekend, and noticed some random globs of grease. First thought was that the guy lubed everything else while he was in there and got a little sloppy. The next day I looked again and there was alot of grease obviously flung around inside the wheel. I found that the outer CV boot is split down inside one of the "accordian" creases. I guess with all the recent activity (lifting to check ball joints, lifting to replace that inner boot clamp, and moving things around for the ball joint replacement) the old rubber just finally gave out.

I'm beating my head on the desk because I ALMOST went ahead and had him replace that shaft while he was doing the ball joints. He probably wouldn't have charged any more since he had it all apart anyway. Now I'm wondering how long before the other side splits a boot.

Good news is that the rear diff cover change went smoothly, other than one rusty bolt that had to be coaxed out with a hammer and chisel....