Ok I thought this was just my car, but my buddies first gen does this to. Is there something blindly obvious that causes an 80 MPH shake in first gens? IM thinking possible idler arm bushings, but im not sure.

 

My red REPU shakes at around that speed too. I blame the tires.

 

Mine doesn't shake at that speed, or 90, or 100. ****, at 80 I can let go of the wheel and the car will keep going on a straight line. Let me think... at 110 it starts to shake a little bit, but I don't often go that fast.

 

Mine did the same thing, until I got new tires.

 

Mine does too....and I HAVE new tires.... balance has been re-checked simply because of this reason.... so........??? dunno homie!

 

I redid suspension, nw bushing, ball joints, tie rods, new tires, and aligned and it got rid of the shake.

 

Do what BigJim did, but do the wheel bearings with it.

 

i did the same as bigjim along with the bearings...although i did it to upgrade the suspension not because it was vibrating cuz it wasn't at all...

yest i took the car upto 95mph for the first time and it was as smooth as it can be...so...dunno at what point mine will vibrate at.

could the driveshaft or u-joints cause this vibration as well? how about the motor or tranny mounts?

 

Sort of not the same, but my '91 Dodge Pickup gets to 95 (what appears to be its limit) with no shakes. Hell, she even takes herself in a straight line still!

 

yea my bearings were all replaced as well forgot to throw that in.

 

Tires out of balance/out of round.

How much more blindingly obvious can you get?

Worn front end components will never cause a shake. Think about it... it takes a LOT of energy to shake the mass of the car. How is that energy generated by a loose bushing? It isn't. However, an out of round tire or an out of balance wheel/tire assembly will shake the car by either mechanical means (tire's radius inconsistent) or inertial means (center of gravity not in the same place as the wheel's axis, so it's always throwing its weight all around shaking the car up and down).

1/4 ounce of imbalance on one tire will be noticeable at only 50mph on a smooth road. Now imagine what an entire ounce of imbalance will do at 80....

 

I'd have to say balance also since I use to have this problem. Most tire balancers will only estimate to a certain weight (maybe 1/4 ounce most times) and may possibly only do the balance at low speed. You need to talk to your balancer and see what they do. I got mine spotted at 55mph and now she is smooth!

 

Standard balancer tolerance is 1/4 ounce.

HOWEVER!

When was the last time the balancer was recalibrated?

Is the balancer shot? (I have seen them go iffy - you can chuck a wheel in there, balance it to zero-zero, rechuck it and it will be off by an ounce or more - WHAT IS CORRECT?)

Is the guy balancing respinning the wheel to check the balance after the weights are on?

If he is, is he shooting for zero-zero or is a quarter-ounce out acceptable to him? (Note that this is often standard practice and it is NOT acceptable for light cars with low-friction steering components like ours - it works just fine on stuff like old Caprices and the like!)

What kind of tire runout is there? 1/16th of an inch can be felt on the front. Just because tires are "NEW" doesn't mean they are round... Goodyear in particular is VERY BAD in the past several years for BRAND NEW tires that are JUNK. And the sad thing is we could not send the tires back as defective... there has to be a customer complaint attached! So customer spends $700 on four hoops and one or two would be junk and we'd have to ship it out KNOWING that the customer would be unhappy.