OK,
I just drove across the country and this problem developed towards the end of my journey. Incidentally this old diesel started right up after sitting for six months, not bad for an old girl. When I step on the brakes, there is an awful shaking that seems to come from everywhere. So I thought it might be the brakes, warped rotor, but they all look good. I tried to stop using the brakes and just downshift, but the shaking remained leading me to think that it is something other than brakes. Could it be the bushings in the rear suspension? i jacked it up to inspect, and they look pretty cracked and worn(a lot of stuff looks that way), but there didn't seem to be any excessive movement. Could even a little play cause this type of vibration?

Also, I've got big tires in the back 205/65 that take up most of the wheel well and I noticed on one side that there are scuff marks on the inside well indicating that somehow the tire moved over to make those marks. Is this further evidence that the real axle is sloppy?

thanks,
jon