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From digest.v7.n246 Tue Sep 23 19:41:56 1997
From: "smcastle" <>
Date: Tue, 9 Sep 1997 10:00:15 -0400
Subject: <E34> Differential Removal (not calculus related)

Some projects are always taken on with a little fear of the unknown. Do I have the right tools? Can it be done? Any secrets worth knowing beforehand? Well, it was time to drop the differential out my car, and all of the above crossed my mind. The only thing which was self evident was that I didn't want the thing crashing down on my forehead after I unbolted it, so the first order of business was to roll the floor jack under it and jack it up just enough to support it's weight.

The car was already up on four stands, so I slid on my back (on the driveway) with my shop light to try and figure out which bolts held the thing in place. I identified my likely candidates, and started. First, remove the driveshaft by unbolting the locking nuts just ahead of the differential. You say, how do you get it not to turn? This took a few minutes for me to figure out (I had already removed the engine and transmission), but then I realized the hand parking brake might do the trick. It works great. The drive shaft then needed just a little tug to pull free from the differential. Next, the half-shafts. These are quite easy to remove using the appropriate sized allen-head wrench and are easily accessible. Again, the parking brake prevented any rotation so it was possible to apply enough force (sadly, no air tools in my garage) to loosen the bolts. Now, all that was left was the differential sitting in it's cradle.

My earlier once-over had identified five bolts which appeared to secure it to the subframe. The first bolt faces forward towards the front of the car. This came free without too much effort. Next, there were two bolts I could see on the side that appeared to attach the diff to a mounting bracket. These were 22mm heads, and naturally I didn't have a 22mm wrench which would fit up in the narrow opening. Job interrupted for a quick trip to Home Depot for a $15 wrench. Bought the polished one, not because it was pretty, but because for whatever reason, it was longer and I knew I needed as much leverage on those bolts as possible. Back under the car, I doused the bolts with penetrating oil, but they don't want to break loose. After much exertion and no result, I encourage the bolts by tapping the end of the wrench with a sledgehammer. Bingo! I loosen them up and remove them.

The last two bolts face the rear of the car. These were 19mm and removed easily. I reached up and unplugged the electrical connector and then got out from underneath and lower the jack very slowly. The diff didn't move. All of the concerns mentioned above flashed through my head again. What had I missed? I decided to jack it up again and coax it out of it's cradle. This time I could see it move. I then lowered the jack again and moved it rearward so I could cause a front tilt on the differential. This worked, and I maneuvered the diff out of its cradle and steadied it on the floor jack as I lowered it. These diffs are REALLY heavy. But anyway, it was out, and what seemed like some incredibly complex project (at least for me) was actually pretty straight forward. The only depressing thing was discovering that those two 22mm bolts I had removed on the side didn't need to have been removed! They were actually bolts holding the bracket that the front bolt secures to. So, in fact, the differential was held in place by only three bolts, the driveshaft, and the halfshafts. Based on my experience, I've concluded swapping out a diff can easily be a DIY project for those so inclined, maybe looking to add a little gearing to their cars.

Steve C.

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