VashtheStampede

so. i still havent fixed the huge-*** rust holes in the back, but its now getting pretty bad. the diff has bounced off of the body twice now on hard launches. well im assuming its the diff. i looked under the car while i pushed it back and forth and could watch the diff tilting up and down. from what i saw in the haynes manual, which is total crap unless you have a 79-80, the rear end only has 6 mounting points which are the upper and lower ?trailing arms? and the two ends of the watts linkage. any ideas of what would enable the diff to tilt? is there any other mount point im unaware of that could be broken?

Hades12

The lower trailing arm is most likey rusted off of the body mounts.

wae

There's another couple mounting points, actually: The shocks. But I don't think that's your problem. =)

Because of the universal joints in the drive shaft, and the fact that the driveshaft can travel fore and aft on the output shaft from the tranny, your differential has plenty of room to travel back and forth, side to side, and to pivot. It's going to travel up and down during normal driving, however, the control arms should keep it from moving around. I would inspect the following:

- The control arms. Hope against hope that one of these has rusted to the point of breaking. That's really easy to fix.
- The rear axle. Hope that you can find one of the control arm mounting brackets rust. That's more expensive, but still pretty easy.
- The frame mounting brackets. These could be rusted to the point of braking loose from the frame. This is pretty bad, but I don't have a lot of experience with that sort of repair.

I suppose there's a possibility that it could be the Watts linkage, but I don't think you'd get much movement on a launch if that was broken loose somehow...

85rotarypower

The watts link keeps the axle from moving from side to side. It has nothing to do with your problem. Your lower control arms (is that what they are?) are probably rusted to the point that they broke off on either the body (most likely spot if your bin rust is bad), or at the axle itself. I don't know if you can fix that though if its because of the bin rust. You risk setting off your rear end alignment and totally screwing up how the car rides.

VashtheStampede

hahahaha risk how the car rides...
i cant imagine how it could ride worse than it already does. ;P

wae

Well... if you weld new sheet metal into place, and weld a new bracket on, if you don't have it aligned absolutely perfectly, your rear axle is going to be at an angle. That means you're never going to be able to get the car aligned right.

So, the ride might be smoother (and, indeed, it would!), but the handling is going to be pretty wonky.