differential broken?

[1980 911 sc]

ok i am having troubles figuring out what is going on here...

the car vibrates when under load This happens to different degrees at different times. sometimes it is a lot and sometimes I cant even feel it, usually after it warms up. So i figured I would give it a tune up, oil change, check my CV's, axles, and wheel bearings and if all that went well it may be a clutch or trans issue.

well when I had it in the air, I rotated the passenger wheel and the driver wheel doesn't move at all and vise versa... as if i have a broken differential, CV, axle, etc. Now, I have broken a CV and I have also broken a stub axle in the last year or so, and both times the car would not move after it broke. This is what happens with an open differential. Paul at Cyntex fixed this both times.

What is wrong here? If the diff is messed up why can I still drive it?

I gotta be honest, i love to DIY, but I lack the facilities. I am also somewhat of a cheap ass (LOL). IF I can fix it in a day or two I will do it, but if I can't figure out what it is ahead of time I am gonna end up taking it to a local shop. I am not afraid to drain the trans, and pull the diff cover etc. and take a look (my current plan of action) but I would do it with a new diff on hand there waiting to be installed.

Any help/advice would be appreciated!

[Gunter]

How exactly did you breake a CV and a stub axle?
CV broke how?
Stub axle?
It can happen that one side doesn't turn and it will still work.
Call your mechanic and ask about this before you go too far with the differential.
Vibration under load can come from a number of things like bad/loose motor/transm. mounts, clutch,............