Rear shake above 70MPH

[NScarpi]

If I can get this fixed, this car will be like new. This is a 95 wagon GL. When I go above 70 there is a shake from the back of the car, the faster you go the worse it gets. Here is what I have done so far: New tires and balancing, swapped front and rear to make sure there wasn't a bad rim, changed one of the rear hubs even though it seemed ok. It didn't make it any better. Checked all the bushings and shocks, all seem fine. I didn't notice this very much because where I live I rarely get above 70, but we are driving to Chicago next week and I will be on highways that allow 75. So it would be nice to not have to put up with this. There is no shake in the steering wheel. Also I put it up on stands and ran it up as fast as it would go without much vibration at all. I figured that even if it appeared to come from the rear, it might be fooling me and be in the front, but the front seems great. I have no way to spin the rear wheels fast enough to see if I could notice something. Any ideas?

Thanks
Nick

[shorod]

Well, if you can find a shop that still has an on-the-car spin balancer, that could get the rear wheels up to something north of 70mph. I don't think these were very popular due to obvious safety reasons, but rare occasions like yours we were glad Dad had one.

Did the old tires show any signs of cupping, specifically the rear tires? Have you inspected the rear struts for evidence of leaking oil? If there is anything that looks like oil around the shock shaft, they are probably ready to be replaced.

How about rear wheel bearings? I don't remember if the '95 has the sealed hubs in the rear or if you can pull the bearings and inspect them. I would expect you'd hear the bearings though before they got bad enough to cause a vibration, but I'm not sure how significant a shake you're talking here.

-Rod

[NScarpi]

I haven't seen one of those old spin balancers since high school, I would love to find someone with one. I really don't remember what the original tires looked like. This has coil springs on the back and there was no oil leaking from the shocks. My parts car has struts so it was of no help. The 95 has sealed bearings in the hubs, and it shakes enough so that at 75 you can see the dash vibrating. I intend to take the car back to where I bought the tires and have them check the balance of the rears, this week. Before I put the tires on it would shake worse at 65 then it does now at 75. After the new tires I thought the problem was solved, it was smooth, but I was driving at 65 or less. The shocks don't seem bad, but you may be right, I don't know how long the person who had this car before me drove it like that. I have had the car on the road for about 3 months. I may have put 2000 miles on it, maybe not even that. Maybe some new shocks would take care of it, I guess that means a parts run in the morning. If I get them changed I will let you know it that fixed it.
Thanks
Nick

[shorod]

Odd, and when you swapped wheels and tires front to rear, the shake didn't become more pronounced in the steering wheel? What you describe seems excessive to be caused just by bad shocks. It seems something would need to start the bounce. I trust you've tried a different stretch of road to make sure it's not just the road you're driving, right?

-Rod

[tripletdaddy]

Here's my Any noises? Did you yank, bang, torque your rear tires REAL hard when up on jacks? Look for looseness at the sway bar and links, the double bar suspension, tension strut, strut to tower bolts and knucle. When is the last time you had the rear end aligned? They could do some of the checking for you when they do the alignment. Maybe the tires are so far off, they are grabbing and slipping causing the vibration. And I would guess it's worse now because you have new tires which would have better grip than the old ones. Just a hunch, nothing scientific or time tested and proven.

[NScarpi]

Let me start by saying that when I put the new tires on it decreased the shake very much. Over the last few days I was able to change the shocks. One was very bad, I guess it would be fair to say that it wasn't doing anything. New shocks did help, and it is good enough to live with. I can cruise at 75 without noticing any dashboard shake, I did take it up to 80 and that wasn't bad either. The shake was still there but not too bad. I did check all the bushings very well when I was under it, all seemed normal. The shocks made enough of a difference that I will be able to make the trip without worry. When I get home I will have the rear alignment checked. And I did check it on a different roads.

Thank You for all your help
Nick