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pipecraze
06-07-2008, 08:24 PM
My car shakes between 70-80 and I can't figure out why.

I've just replaced:
upper and lower contol arms
Front end links
Outter tie rod ends...inners still tight
strut rod bushings at the control arm...at frame still tight.
Engine mounts
KYB shocks are about 4-5 years old
New tires just put on a week ago...balanced and alignment done
Steering rack was replaced about 3 years ago with new bushings, they don't look in great shape though

I've purchased all new rear bushing but haven't put them on yet. Shaking feels like its from the front end though.

It also makes somewhat of a clunking noise over uneven pavement. After everything that I replaced I wasn't too happy to hear that!

I have a feeling that the clunking noise is related to the shaking at highway speeds but not sure.

I was planning to get the tires rebalanced but before I do that I thought I'd hit you gus up for ideas on either!

franky_402
06-07-2008, 08:42 PM
i work at a tire shop and we get alot of cars shaking, go get them rebalanced and if you can watch them do it, i know some of my friends will get lazy and just hammer the weights wherever they want so it looks balanced!!!

scbird1
06-07-2008, 08:54 PM
Check your tail shaft of your trans. 4R70W`s tend to have the tail shaft bolts back out. Also have you ever removed your drive shaft? If so you might need to rotate it 180 on the pumkin. Try switching your back tires to the front.

pipecraze
06-07-2008, 11:39 PM
Thanks for the ideas thus far! I'm going to check out the tail shaft tomorrow and post back! Any other drivetrain ideas! I've had this prob with both the new and old tires!

What do you guys think of this. The ring on my harmonic balancer is loose...I think one of the bolts fell out. It's def not balanced now...you guys think that could cause the shaking. I have a BHJ but have yet to install it!

I may take the car out tonight, get it up to 70, then put it in Neutral....see if the shaking goes away when the rpm's drop....that would rule out the tires.

franky_402
06-07-2008, 11:47 PM
if the bolt broke on the balancer broke i would not drive it, you could snap the crankshaft, i would get that new balancer on asap

pipecraze
06-08-2008, 12:18 AM
The center bolt is fine. I think one of the small bolts that holds on the ring came out. The ring is loose.

dwayne
06-08-2008, 02:55 AM
if the bolt broke on the balancer broke i would not drive it, you could snap the crankshaft, i would get that new balancer on asap



that may be your problem,agreed with above post.also have you checked out the u-joints on driveshaft for any play in them.

TbirdSCFan
06-09-2008, 10:26 AM
It also makes somewhat of a clunking noise over uneven pavement. After everything that I replaced I wasn't too happy to hear that!

I have a feeling that the clunking noise is related to the shaking at highway speeds but not sure. Check/tighten the subframe bolts. Also, I trashed a set of cheapo end links in less than 2 days of track work. :rolleyes: Don't assume that they're any good. Check the condition of the endlinks/lower ball joints by putting a jack under the LCA and raising it up to where its at normal ride height. Then wedge a breaker bar under the sway bar, where the end link attaches, and inth the spot where the shock mount to the LCA. Grab the breaker bar and pull up with all you've got! Nothing should give at all. That should help you find your clunk. :cool:

89XR7TD
06-09-2008, 11:14 PM
Keywords: I've had this prob with both the new and old tires! So that is ruled out but I'd check to see if any of the rims maybe bent?

Also if you go back to get re-balance ask them to do the Harmonic Balance not just a regular speed balance!!

Tom

pipecraze
06-10-2008, 10:04 PM
Keywords: I've had this prob with both the new and old tires! So that is ruled out but I'd check to see if any of the rims maybe bent?

Also if you go back to get re-balance ask them to do the Harmonic Balance not just a regular speed balance!!

Tom

I took the car out, got it up to speed, and put it in Neutral shile it was shaking. It was still shaking when the rpm's dropped.

I'm going to re-balance the tires. I'll ask for the harmonic balance too! Thanks!

SuperCharged91
06-10-2008, 10:06 PM
Check your U-Joints it happened on my Car and the U-Joints were loose

Young-SC-Owner
06-10-2008, 10:20 PM
I'll ask for the harmonic balance too! Thanks!
No no
Harmonic balancer! green bean!!!

Its what the crank pulley is connected to..
(The big pulley in front of the radiator the farthest down)

tim hagewood
06-10-2008, 11:11 PM
I have 93 SC had the same problem it was the halfshaft bearing on th rear. Just an idea

89XR7TD
06-11-2008, 01:55 PM
No no
Harmonic balancer! green bean!!!

Its what the crank pulley is connected to..
(The big pulley in front of the radiator the farthest down)

There is a type of Harmonic balance on wheel tire assembly thats what I'm talkin about not the Harmonic balancer its self, just to clear things up!!!A wheel on the balancer machine comes down and pushes up against the tire and measures road force and also measures if the tire is out of round and can also tell you if the wheel is bent slightly!!!

But some places do not include this cause there wheel balancer is old as time!!!

Tom

cbt
06-13-2008, 01:07 PM
check u-joints
check the drive shaft bolts at the rear-end

ThunderDave
06-13-2008, 07:27 PM
I have recently noticed that mine starts to shake/vibrate around 70-75. I've had all the front end redone and recently had tires balanced and alignment done. On firm ride you can feel it, but on soft you can't. :confused:

I'm thinking about putting rear tires on front and see if that solves it. If so, I''ll go have the tires rebalanced.

1990XR7SC
06-14-2008, 11:43 AM
well you would think if the rpm dropped that it would rule out the u- joints. but they are running at the speed you were running before you shifted into neutral. But also it takes off the torque thats put to it. only way to be sure is to check the play in it with it on the ground. or something holding your rear wheeles. But the rear end bering being shot is possible. but unlikely. See if the rims are bent if so replace. and def a rebalence of the tires since wheel weights can fall off.

TbirdSCFan
06-14-2008, 07:19 PM
I have recently noticed that mine starts to shake/vibrate around 70-75. I've had all the front end redone and recently had tires balanced and alignment done. On firm ride you can feel it, but on soft you can't. :confused:

I'm thinking about putting rear tires on front and see if that solves it. If so, I''ll go have the tires rebalanced. What about the rear suspension?

ThunderDave
06-14-2008, 09:23 PM
What about the rear suspension?

Haven't done anything with the rear, but the vibration certainly seems to be in the front.

SuperCharged91
06-14-2008, 10:36 PM
well you would think if the rpm dropped that it would rule out the u- joints. but they are running at the speed you were running before you shifted into neutral. But also it takes off the torque thats put to it. only way to be sure is to check the play in it with it on the ground. or something holding your rear wheeles. But the rear end bering being shot is possible. but unlikely. See if the rims are bent if so replace. and def a rebalence of the tires since wheel weights can fall off.

No my U-Joints were loose and it was shaking at 70 and over if it was in neutral or in gear

slowpoke
06-15-2008, 01:44 AM
when i got my sc it was real bad, not sure what it was due to i did a 100% rebuild of the front end. have had it up to 169mph and no shaking. cost me about 600 in parts and did the work myself. extra 160 for alinement. get the life time its worth it. after setting it had to be redone 3 times.

pipecraze
06-15-2008, 12:05 PM
I'm still looking into this. I haven't been able to re-balance my tires or get underneath to check ujoints and such. Will post back after problem is resolved.

TbirdSCFan
06-15-2008, 12:33 PM
Haven't done anything with the rear, but the vibration certainly seems to be in the front. I've got a small amount that is due to worn rear bushings. It not a lot, but enough to notice on the road and it can be deceptive. If you want to check, its rather simple to do. Raise the rear up on jack stands, chock the front wheels and run it to see what if any vibration is coming from the rear. In this case the driveline is unloaded, so easy on/off the gas and brake. I've had a vibration from loose driveshaft bolts that drove me nuts for a while. That's something to look at also. Those are best fixed with locktite.

ThunderDave
06-15-2008, 02:15 PM
I'll check those out. Thanks

SCarSC
06-15-2008, 06:42 PM
Shaking on mine at anything over sixty was due to bolts connecting the drive shaft to the pumpkin, they were loosened up significantly. Tightened them down with a 12 mm closed end wrench and the vibration went away.

ThunderDave
06-21-2008, 11:42 AM
Damon states in this post http://www.sccoa.com/forums/showpost.php?p=748944&postcount=5 that the crank pulley and balancer are balanced as a unit. When I got this 89 together, I can't remember if I used a different pulley or not, but recently took the under drive pullies off that I had put on and replaced it with the stock crank pulley I had. Could that be the cause of my vibration. I can't say I remember having it before this.

And there probably was enough vibration in the front end before, that I didn't notice the vibration from the crank pulley, if that is the problem. I know the right thing to do would be get a BHJ and aluminum crank pulley, but the money just isn't there right now. What else can I do other than that?

getblown
06-21-2008, 01:24 PM
Shaking on mine at anything over sixty was due to bolts connecting the drive shaft to the pumpkin, they were loosened up significantly. Tightened them down with a 12 mm closed end wrench and the vibration went away.

Nobody addressed that it is only at 70-80mph which would have to be a rotating assembly from the tailshaft (dont think so) to the tires. It would have nothing to do with the engine.

If the car has had the snot beat out of it for a long time, the U-joints are possible, but from personal experience check the driveshaft bolts like the guy above posted. Tires or Driveshaft bolts.

jOe