[Guest]

I know i shouldn't be going very fast in an old wagon with so many miles but I couldn't help it . Whenever I start passing 100 mph the car shakes uncontrollably. It doesn't matter how much weight is in the car too. Whether there are 4 people or just myself the same thing happens. Why is that? Anyone have any ideas????

 

[Guest]

It's most likely caused by either the driveshaft or wheels being unbalanced at that high of an RPM.

 

[Guest]

The vibration is not due to unbalanced wheels. At high speeds Centrifugal force takes over and vibrations due to unbalanced wheels is not felt, that is why if you have a unbalanced wheel you might have a vibration from 40 o 55 mph then at higher speeds lets say 70 mph the vibration goes away, that is why tire balancers only spin the tire at speeds around 55 mph. Your real problem is having 300k + miles.

 

[Guest]

That's interesting considering after I had the RE730's installed on the '94 it had a vibration above ~75 mph that wasn't there with the ZR4's...

 

[Guest]

That was just an example, sure you can have vibrations at 75 mph due to improperly balanced tires, but if the problem causing the vibration is a poorly imbalanced tire then the vibration will eventually go away at higher speeds. Other factors can cause vibrations besides balancing, bad wear, bent wheel, etc..

 

[Guest]

it isn't right to say it is because the car has 300K miles and thats that either, becuase if a car is properly maintained, and certain parts (like the tranny and probably the engine) are rebuilt, it could be mechanically just fine. I'd say check your bearings, your rims for bends, get the balanced on the new Hunter balancer that actually load balances them. I bet the car can be made to do 100 MPH + burst without shaking violently without a lot of work. My old 9C1 had 146K miles on it and it felt great up in the 130's (got scary in the 140's but not shaking violently). I realize thats half the mileage, but still quite high.

 

[Guest]

The question of what causes a vibration at high speeds is not one that has an obvious answer. I had a vibration problem that started at about 75 mph and continued right up to and over 100mph. I thought it could be my new Bridgestone Potenza RE730's, it wasn't! I thought it was the balancing that was done when they were installed at a local garage, so I found a shop with the new HUNTER GSP9700 machine <http://www.hunter.com/>, but that wasn't the problem either ... although the balance was not accurate and now there is no balance related vibration. I thought it might be engine mounts, torque converter related (really reaching <g> ),or maybe pinion angle. It was none of those things. I knew it was not my front end because I had rebuilt the front end and replaced _everything_. The problem ended up being related to my aluminum driveshaft. Trust me, the discovery of this problem was not an easy find. BTW, the vibration was somewhat intermittent. So, what I am saying is that you cannot rule out anything but, like with anything else, start with the obvious and work your way through it ... with a little help from your friends. <g>

Good luck,
Peter

 

[Guest]

Peter, could you post info on your wagon? I have heard good things about it. Any long term impressions that you could share?