1990 GMC Safari Steering wheel shake

Greetings. I am in need of some assistance diagnosing a steering wheel shake in my Safari. The steering wheel shakes in an up/down direction once
the vehicle reaches 67 mph and continues through higher speeds. Here is what I have done so far:
- Rotate and balance tires - Check alignment - New front brakes and turned rotors - New front bearings, Timken - New shocks (4) - New engine mounts, both were broken, had them replaced this week. - The Auto Service Center said the suspension looks good and tight.
After having the motor mounts replaced, the shake is subdued, but definitely still there. It's as if what ever is causing the shake, was magnified by the broken motor mounts.
The tires are Goodyear Integrity and have about 20,000 miles. However, a slight shake existed even when the new tires were installed. One Goodyear dealer said I had two bent wheels, but another dealer said my tires were out of round. So, I bought the Integrity's.
Aside from buying new wheels and tires, I do not know what else to try. Can anyone offer any suggestions of what to look at?
Thank you, David
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I would have the ft tires balanced on a road force balancer, Hunter is one type.

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The Road Force Balancer was also suggested by the Auto Service Company that replaced the motor mounts. They recommended a FireStone Tire store with the equipment. I called the FireStone and the cost is $22 per wheel. Ouch. But I suppose that is much less expensive than just buying all new wheels and tires.
Thanks for the advice.

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"Palmer" wrote: RE: 1990 GMC Safari
The steering wheel shakes in an up/down direction once the vehicle reaches 67 mph and continues through higher speeds. Here is what I have done so far:
< Extensive front end work and motor mount replacement >
After motor mount replacement the shake is subdued, but still there. It's as if what ever is causing the shake was magnified by the broken motor mounts.
I do not know what else to try. Can anyone offer any suggestions of what to look at? ______________________________________________
In RWD vehicles that vibration sometimes results from bad universal joints or broken transmission mounts.
Good luck.
Rodan.
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Perhaps whatever is shaking your steering wheel is what previously did a number on the motor mounts, and is working on doing a number on the mounts you just replaced. I would be looking at motor to tranny hookup.

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when you say up and down are you meaning a left and right oscillation or like the tilting of the steering wheel?
Did you have them check the wear indicators on the ball joints?
TM

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could your clutch fan be seized or part way there I had that happen to my astro van

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The Auto Service Center that replaced my motor mounts also checked all suspension components and said everything looked very good.
I had the Road Force Balance done at a local Tire store called S&S Tire, and the shake is gone. One of the front tires needed to be turned on the rim to bring it within some kind of tolerance, he did say that a regular balancer would not have indicated a problem.
The Balancer did determine that one of the tires has some kind of wobble and may be separating. I'm taking it to Goodyear tomorrow to see if there is enough warranty to replace the tire.
Thank you for all the great advise.

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