1987 Chevy r10 front end vibration at highway speed

[chengny]

BTW, did you do as MrMarty51 suggested:

Tr4y installing the rear tires on the front, see if it still shakes then.

That is a very useful diagnostic. If you have not done this yet, you should - before investigating anything else.

 

[LB2387]

There doesnt really seem to be any way to control the shaking. It seems to start as soon as it hits the 65-75 mph range, and smooths out around 85. The majority of the vibration is in the steering wheel, but a little bit in the pedal as well. It feel like the steering wheel is shaking more up and down rather than side to side. And it shakes hard enough to have a pretty big vibration amplitude(if you know what I mean). Doesnt really build up. All body mounts, core support mounts, engine mounts, and tranny mount have all been replaced within the last year. Transmission was rebuilt less than a year ago. I checked the rag joint it was nice and tight, with no signs of wear. The bearing on the bottom of the steering shaft had a little bit of play in it, but not sure if its enough to cause the problem. Could be suspect though.