Horrible Shake

I just bought a 1992 XJ Sport of ebay. I was driving it home this weekend (10 hour drive). I've got two major issues with this vehicle and was wondering if anyone could help me out.

First is this: While driving at speeds equal to and greater than 70mph on the interstate, I'm ok unitl I hit a bump in the road (ie a pothole repair or a transition from the asphalt road to a bridge). All the sudden the Jeep starts shaking really really bad. I hit the brakes and slow down to 45 mph and the shaking stops. I can then accelerate back up to 70 and nothing happens until I hit another bump and it will shake the whole truck again. It doesn't just vibrate the steering wheel, but the entire vehicle. It won't shake like this at 60 or 65 mph...only around 70. Any thoughts as to what this is?

Second, my speedometer works but the odometer doesn't. Does anyone know what I can do to get this fixed?

Thanks for the advice.
BAMA

hey on the wobble problem try replacing your steering stablizer(the shock on your tie rod/drag link assembly) mine was doing the same thing and it scared the bejebus out of me.. if that doesnt help check the tir rod and D.L. joints.. as mine were all shot since it was an older xj..

To solve the DW problem, you might also try inspecting the ball joints for play and the bearing assemblies. Mine did the same exact thing you describe. I replaced those parts and it took care of itself. Also check the tires. Uneven wear can cause some peculiar vibratons...also seaking from experience...:doh:

X2 on the stabilizer. I just had the same problem. The shaking got so bad once it thru out my trac-bar as well. Death Wobble is no fun on the expressway.