Front End Shimmey

[chevyaddict]

I just took one of our company vehicles to Ar. It shimmied when the brakes were applied. Have you checked the rotors??

It doesn't shimmey when the brakes are applied... only when there are bumps in the road mutually exclusive of braking.

 

[Art Jett]

It wasn't on a vette, but I had the same problem with my truck a while back. It turned out to be the front tires. Apparently one of them had a bad belt that would caust this after hitting a pretty good size bump. I put new tires on it and never had it happen again. Maybe just something elst to look at. It would be pretty easy to put different wheels and tires on it with all the chevys you have for a try.

 

[chevyaddict]

It wasn't on a vette, but I had the same problem with my truck a while back. It turned out to be the front tires. Apparently one of them had a bad belt that would caust this after hitting a pretty good size bump. I put new tires on it and never had it happen again. Maybe just something elst to look at. It would be pretty easy to put different wheels and tires on it with all the chevys you have for a try.

I have BRAND NEW tires on it... less than 100 miles on the tires.... thanks though!

 

[chevyaddict]

Update, well not really

Well, I finally got around to putting the hoses on..... of course that wasn't the problem to begin with. Been enjoying her the past couple of days but that shimmeying is gonna tear the car apart.

Now, everyone has offered up some good suggestions such as:
Bad Idler Arm
Bad Ball Joints
Bad Tie Rod Ends

However, isn't it true if any one of these were bad, when you jacked up the car you would be able to tug at one of the wheels and have that "looseness" manifest? In other words, there would be play in the system, yes? That is NOT THE CASE. She is TIGHT. Now, perhaps I can't tell by just tugging but that has worked for me before, especially if its the idler arm.

Another thing - if the shocks were bad, wouldn't that cause and "up and down" shimmey? That is not what is happening, its definitely a "right to left" shimmey....

I'm thinking its that steering cylinder, but don't want to spend a buttload of money to replace it just to find out that wasn't the culprit. Isn't it true that the steering cylinder is what buffers the car from shimmeying and makes the front end tight? Or is the front end tight regardless of this??

 

[wishuwerehere82]

Yes Dawn,
You would be able to feel the looseness in any of the above steering components.
One problem I had on my 82 was that the bracket that is at the end of the steering cylinder that anchors to the frame, was loose. The bolts that hold it to the frame had un-bolted, such that when the cylinder worked back and forth the bracket was just wiggling back and forth with nothing to push on. The bushings on the steering rod end were also worn out, and were not transmitting force to the bracket.
The steering control valve on the steering relay rod is actuated off the pittman arm on the steering box, and controls the fluid flow to the steering assist cylinder. If the link is loose, it will give a substantial wiggle in the steering, especially on curves.
Unless the steering assist cylinder is leaking fluid, I don't think there's any reason to change it.

So check your pittman arm, steering assist cylinder, control valve, and anchor bracket.

 

[purpleRac3r]

It is possible that a brand new tire can cause vibration and/or shimmy. A tire can be molded out of round, so much so that a regular balancing can't sufficiently correct it. Usually it's more noticeable on tall sidewall bias ply tires, but can happen on any type of tire. It's also possible that the new tires weren't properly balanced to begin with. It would be interesting if the shimmy made its appearance shortly after the new tires were installed. A trip back the tire shop for a balance check could be worthwhile. And it shouldn't cost anything.

 

[chevyaddict]

Yes Dawn,
You would be able to feel the looseness in any of the above steering components.
One problem I had on my 82 was that the bracket that is at the end of the steering cylinder that anchors to the frame, was loose. The bolts that hold it to the frame had un-bolted, such that when the cylinder worked back and forth the bracket was just wiggling back and forth with nothing to push on. The bushings on the steering rod end were also worn out, and were not transmitting force to the bracket.
The steering control valve on the steering relay rod is actuated off the pittman arm on the steering box, and controls the fluid flow to the steering assist cylinder. If the link is loose, it will give a substantial wiggle in the steering, especially on curves.
Unless the steering assist cylinder is leaking fluid, I don't think there's any reason to change it.

So check your pittman arm, steering assist cylinder, control valve, and anchor bracket.

I'm reiterating some of what I said in the PM here so others following along can have more info too!

I was very excited about your bracket hypothesis so I immediately looked at that but it is very solid.... no problems there. I had the car up again yesterday with my boyfriend and we looked and looked and tugged and tugged and everything is solid - way solid. Now, one thing I did notice, the only movement anywhere is a very slight movement right where the control valve is.... but I think that is normal movement, it shifts around about a half inch or so if you have the entire front end up and really tug hard at the front end, you can get it to move some.... is that little bit of play normal? If it is then the only thing I can think is that just overall wear in the entire system is causing this... but I'm still very suspicious. Its SO SMOOTH on smooth roads - you'd never know there was a problem, its only when a hard bump or a rough road comes my way and all hell breaks loose!

 

[chevyaddict]

It is possible that a brand new tire can cause vibration and/or shimmy. A tire can be molded out of round, so much so that a regular balancing can't sufficiently correct it. Usually it's more noticeable on tall sidewall bias ply tires, but can happen on any type of tire. It's also possible that the new tires weren't properly balanced to begin with. It would be interesting if the shimmy made its appearance shortly after the new tires were installed. A trip back the tire shop for a balance check could be worthwhile. And it shouldn't cost anything.

Thanks, but if what you were describing is true I'd feel it all the time... on smooth roads everything is perfect, and when I turn everything is perfect too. I'm only feeling this on a really rough road or when I hit a bit bump.

 

[gmjunkie]

Thanks, but if what you were describing is true I'd feel it all the time... on smooth roads everything is perfect, and when I turn everything is perfect too. I'm only feeling this on a really rough road or when I hit a bit bump.

This may sound Stupid, But hows the Breaks???? As I recall back Mini,Mini,Mini years ago when I owned My First Vette(68 427 Roadster) I had a Similar Situation acting like you describe and it ended up being the front calipers dragging!!! It would SHAKE the Crap right out of you,and if the hard top was off it would really Amplify!!!

 

[chevyaddict]

This may sound Stupid, But hows the Breaks???? As I recall back Mini,Mini,Mini years ago when I owned My First Vette(68 427 Roadster) I had a Similar Situation acting like you describe and it ended up being the front calipers dragging!!! It would SHAKE the Crap right out of you,and if the hard top was off it would really Amplify!!!

Brakes work like a charm and the behavior I'm describing is not correlated with braking at all... In fact, I've replaced both front calipers already last year.

 

[gmjunkie]

Brakes work like a charm and the behavior I'm describing is not correlated with braking at all... In fact, I've replaced both front calipers already last year.

Mine didn't either other than,if I lightly put my foot on the brake it would stop shimmying!!!

 

[craig32]

Dawn, any luck yet? My 81 does the same thing, one particular spot in the road about pulls the wheel out of my hand, but I drive over it every day in my Monte going to work and nothing. The shock theory is sounding possible to me, as I have replaced all 4 ball joints and had the car aligned, and front wheels balanced, even though one is bent. It does shimmy at about 70, but that is the wheel. I haven't looked into the shocks, so maybe that's the problem with mine.
On another note, what pulleys are you looking for, as in what diameter? Do they have serial numbers on them too?

Craig

 

[chevyaddict]

Dawn, any luck yet? My 81 does the same thing, one particular spot in the road about pulls the wheel out of my hand, but I drive over it every day in my Monte going to work and nothing. The shock theory is sounding possible to me, as I have replaced all 4 ball joints and had the car aligned, and front wheels balanced, even though one is bent. It does shimmy at about 70, but that is the wheel. I haven't looked into the shocks, so maybe that's the problem with mine.
On another note, what pulleys are you looking for, as in what diameter? Do they have serial numbers on them too?

Craig

Well, it doesn't "pull it out of my hands"... the whole car just shakes, but the shake definitely comes from the front. Not up and down shake (like bad shocks) back and forth/ left and right shakes. The smog pulley won't work - it seems these crank pulleys are unique to 68. fun fun, thanks though!!

 

[craig32]

The smog pulley won't work - it seems these crank pulleys are unique to 68. fun fun, thanks though!!

I meant that I have some odd pulleys off of other engines, maybe something will fit. The smog pump pulley runs off of the water pump, doesn't it?

 

[chevyaddict]

I meant that I have some odd pulleys off of other engines, maybe something will fit. The smog pump pulley runs off of the water pump, doesn't it?

This is off my 68 - not my 81.... so no smog pump!!! The 81 pulleys won't work on the 68 unfortunately.

 

[KANE]

Well, it doesn't "pull it out of my hands"... the whole car just shakes, but the shake definitely comes from the front. Not up and down shake (like bad shocks) back and forth/ left and right shakes. The smog pulley won't work - it seems these crank pulleys are unique to 68. fun fun, thanks though!!

How about your engine mounts- are they bad? Those will create a wierd vibration if they are bad.

 

[chevyaddict]

How about your engine mounts- are they bad? Those will create a wierd vibration if they are bad.

They are great.... I should have been more clear - I do feel it in the steering wheel, just not to the point that I have a hard time steering it... its definitely front suspension related... the question is just WHAT!!! ha ha!! Thanks!

 

[craig32]

This is off my 68 - not my 81.... so no smog pump!!! The 81 pulleys won't work on the 68 unfortunately.

Yes, I know we are talking about your 68. I don't know where talk of a smog pump started, but it wasn't me. The spare pulleys I have probably came off of a 69 327. Just wondering if they might work for you, if they had a specific size or part number.

 

[chevyaddict]

Yes, I know we are talking about your 68. I don't know where talk of a smog pump started, but it wasn't me. The spare pulleys I have probably came off of a 69 327. Just wondering if they might work for you, if they had a specific size or part number.

I don't either :confused .... lordy lordy.... I think I definitely need a vacation!!!! Thanks Craig! According to the Ecklers catalog, 68 PS crank pulley is unique to 68, however the 69 2-groove crank pulley will work as the part #'s are the same.... although what is tripping me up is for 68 it says "EXCEPT AC", but that doesn't make any sense as the PS pulley goes on top of the 2-groove pulley. Weird. It also appears that the 68&69 water pump pulleys are the same, although in the catalog it just shows the 2-groove pulley and not the single additional one that I have... The pulleys are still on the car as they aren't bent to the point of non-drivability but I should replace them. Are your pulleys for sure TRUE and not out of round? How much you want for them???

 

[minifridge1138]

You say it happens when you hit a bump. Does that mean when you hit a bump with 1 tire or with both?

I agree that if it was something as simple as the tires being out of balance, then you'd notice it all the time. You said the tires are new with < 100 miles on them. Did the problem start within the last 100 miles? Maybe something was damaged when the tires were changed.