I had an interesting experience today. I've been trying to figure out what my rearend gear ratio is. I only know that its a posi unit and since there are no tags on the diff, I decided to run the car at different speeds,note the rpm's and use the gear speed calculator to give me a ballpark. On my way back home, I slowed almost to a stop at an intersection before making a sharp uphill right turn. When I accelerated mildly through the turn, I heard a sharp snap from the back of the car and the rear seemed to squat a bit. As I slowed to a stop there was a grinding/shaking/bumping action in the rearend. My first thought was that a drive axle or a U-joint had failed. The right rear wheel seemed to be at a noticeable negative camber (leaning in at the top)and I looked under to see what was broken. Everything seemed intact. Joints, axles, control arms, shocks - nothing seemed out of place. I got in and very slowly pulled ahead a few feet. The grinding and bumping continued even at walking speed. Further checks revealed nothing. I was about half a mile from home so I limped it home VERY slowly and jacked up the rear. By now I'm thinking wheel bearing, axle u-joint or the rearend itself is shot. After spinning the wheels, crawling around and checking everything and still finding nothing. I lay under the car and had Pauline spin the wheels by hand. Well at a certain point on the rotation, the entire rear end assembly gave a big shake. 3 of the 4 bolts holding the differential housing to the frame had sheared off leaving one shaky bolt barely holding it on.
What would cause this to happen? I would expect a lot of things in the rear end to let go but not the diff mounting bolts! The car has been driven fast on twisting roads and a small course on an old airbase. I have launched hard on a measured 1/4 mile and spun the tires a few times on the street, but generally it hasn't been abused at all.
A few questions:
What's the basic procedure for dropping the rear suspension?
What are the specs on the four mounting bolts?
Is there anything else I should check as a possible cause for the shearing?

Any help would be appreciated.



Tropical Buzz