I have a 1990 Suburban 5.7 engine auto trans 4x4. The truck has 280,000 miles. while traveling at speeds above 35 if I am not accelerating or decelerating(just cruising) I get a terrible shake in the rear of the truck. It is not the wheels and tires because it is only intermittent. When it starts shaking if I let all the way off the gas or give it more gas it goes away. I thought it was the overdrive but if I pull the gear selector down into drive I still have it.

Any help would be great.

Thanks
Joe

 

have you done any work on the tiers, axles, trany, or any thing on the back half of your ride? can you feel the vibration in the steering wheel or all through the truck?

 

mainly the rearend. I ruled out the tires and wheels because the shake is not all the time. I thought it was the overdrive shifting in and out of OD but I drove the truck in drive and it still does it. I replaced the u-joints but I have not done anything else.

Joe

 

i dont think its your tranny, it may be bad barings , off balance drive shaft, cv joint, or the axels. its more likely not the tranny but some thing in the rear, lose, going bad, or off balance .

 

Of course you have checked the trans mount.

 

I did replace the trans mount with a new one. Could it be something in the rearend?

Joe

 

I was going to say U joints but I think your driveshaft isnt balanced. One of the counterweights may have rusted off or fallen off. Crawl under and look for a weight at the front and rear of the driveshaft. I bet you only have one there.