60 mph shimmy

    Hi all,


    I'm new here (at least as far as posting on the board), and I have a problem I need help with. I just bought '65 K convertible and the car is just beautiful. The only problem is at 60 mph the car vibrates badly. I've had the alignment checked, the wheels balanced and the inner and outer wheel bearings replaced (which I doubt needed replacing), but the car still vibrates at 60. I now believe it's either the wheels or the tires. The tires are radials, and the car has the period correct styled steel wheels. At this point I suspect the wheels are out-of-round, but I would prefer to not go to the expense of replacing them if that turned out not to be the problem (again). Does anyone here have any insight to this problem?


    Thanks,

    Kerry

    You need to check the drive line too.


    I'd take the driveshaft and have new u-joints put in and a re-balance performed.


    While you are under the car check out the transmission mount and rear axle pinion angle.


    All of these can cause "at speed" vibration problems too.

    On your wheel balance, was it balanced hub or lug centric. Styled steel wheels need to be Lug centric balanced. I have a similar problem at 55MPH. I have replaced a wheel I've been told is out of round with no improvement. Now I'm being told my tires might have a flat spot. Mine is felt in the front end only, and does not go away when I engage the clutch. The shimmy is not terribly bad, though. I wouldn't call mine a vibration, just a shimmy.


    I'll be rotating my tires front to back this weekend to see if it improves.

    Hi,

    This was discussed, in detail, some time ago

    and you can find more information by performing

    an advanced search. Don't forget to check archived

    posts.

    /Bo

    66gtk,


    Mine feels like it's in the front end, too. At 55, it feels like a shimmy, at 60, it's more like a vibration. At 60, I would put it in the "not safe to drive at this speed" category.


    I've had the tires balanced three times in the last week (three different places). It has made only a minor difference. I don't know for a fact how they were balanced, but I would guess hub centric.


    I've only had the car a couple of weeks, and I do suspect the car sat for a relatively long time. The radials on the car are pretty cheap (Nitto N470). I'm wondering if they have flat spots. Is there any way to tell for sure?


    BTW, I have a 66 K-Kode GT, too. It has what I believe are original styled steel wheels, and it drives extremely well.


    Kerry

    <BLOCKQUOTE id=quote><font size=1 face="Verdana" id=quote>quote:<hr height=1 noshade id=quote>BTW, I have a 66 K-Kode GT, too. It has what I believe are original styled steel wheels, and it drives extremely well <hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana" size=2 id=quote>

    If you think it is a tire/wheel issue take the tire/wheels off your other Mustang & put them on the car you are having a problem with take it out for a ride & see what happens.

    My shimmy goes away at about 60 MPH and then all is great again! Sorry to hear your troubles. I'd try swapping out the wheels/tires with a trial set to see what happens. That's what I'm considering doing, but I don't have a spare Mustang laying around yet!

    66gtk,


    I work for a loudspeaker manufacturer in Indianapolis.


    Switching the tires & wheels had occurred to me, I just thought someone might be familiar with this issue and point to one or the other as the more likely candidate.


    I'll try and switch the wheels & tires tomorrow (Sunday), and report back. At least that will give me the peace of mind that something more major isn't wrong with the car.


    I haven't had a chance to get any pictures, yet. Most of my free tiem has been spent dealing with this issue.


    Thanks,

    Kerry

    Well...I got the wheels & tires swapped (and then swapped back). Man...what a pain.


    I didn't get the answer I was expecting. The car still shimmy's, but now it worse at 55 mph, and is much better at 60.


    I guess I'll move on to the brake rotors. That's seems the next logical choice.


    Kerry

    I had shimmy problem for years on a 57 T-Bird. I had the tires balanced many times by many shops. Never got corrected until I took the car to the local Lexus dealership. Someone told me the Lexus dealer has a super duper $45,000 balancing machine. I took the T-Bird to the Lexus dealer and, like magic, the shimmy problem was fixed. Those guys at the dealership really got a kick out of working on a classic T-Bird too. I recommend you give them a try.


    Bill G.

    Kerry ,you could have two different sources of vibration in your car ,it sounds like the tire swap was not a fix.i would index the drive shaft ,mark it and the rear diff yoke, disconnect it and rotate it 180 on the yoke, road test see if it changes in any thing, also you can have the wheels and tires road force balanced this is what we do at the ford dealer i work for when there is a harsh vibration ,what it does is index the tire to the rim for minimum runout, the tires may have to be dismounted from the rims and rotated for optimum balance runout, also check for a bent axel flange and front hub flanges for exess runout, good luck, chuck.


    Edited by - chucks302 on 05/21/2007 06:55:24

    Check the bushing in your tailshaft housing and the slip yoke on the driveshaft. Most K codes (and about any 40 year old car), either restored and unrestored, never get these items changed, and they are only good for about 75k miles on a manual trans car that got beat on in it's early days.


    While the shaft is out, get it checked for strightness and balance. Best $120 I spent on the Kar. Made it like new. ($20 for the yoke, $100 for the shaft work).


    I also chased a vibration for a whole summer. Never stopped to think about the yoke and bushing until I took the shaft in to get balanced and the guy said he wouldn't touch it unless I brought him a new yoke. It was actually hour glass shaped, but you couldn't see it with the naked eye. He mic'd it and showed me the taper/out of round.


    So I went home, pulled the output seal and bushing. BINGO! Bushing was wasted. Installed the new stuff and it is smooth as silk up to 100mph.

    I replaced the u-joints on my car in 2000. I didn't realize it at the time, but the cups going to the 9" rear pinion are 1/16" larger in diameter and requires a different u-joint than what is on the front yoke. Until I discovered this error, my car would vibrate above 60 mph. I changed it out with the correct u-joint and all vibrations went away.

    Several years ago I had a 55-60 mph "shimmy/vibration" on my 65 A code convertible. The car had new reproduction SS wheels by Specialty and a new set of Coker 6.95x14 dual-redline bias ply tires. I found a local alignment shop that used an old on-the-car tire balancer with a strobe light that almost eliminated the shake. Only problem- you couldn't rotate without losing the relative balance.

    I appreciate all the feedback I have received over this issue the last few days. I'm surprised by the number of suggestions related to the drivetrain. It doesn't seem like the problem is coming from that area, but I guess I should reconsider that opinion.


    One thing I did notice while changing the wheels, was one of the rear leaf spring is sagging (about 5/8"). I've thought about it, and while I don't believe this is the cause of the problem, I could see how it might aggrevate the situation. In any case, I decided to go ahead and have them replaced (and eliminate that as an issue) before I do any more investigation into the shimmy. Hopefully, I'll have this completed before the end of next week.


    I'll let eveyone know what I find...

    Kerry

    If your looking to have a driveshaft replaced I'd like to recommend D&R Driveline Inc. I just picked mine up today and they did a GREAT job. New custom shaft with U-joints, balanced, even clear coated it, out the door for $160. They do everything from narrowing housings, custom axles, etc. etc. etc. They are a great group of guys to work with and really go out of their way to help you out. D&R Driveline Inc. 768 Chicago Dr., Jenison, Mich. 1-616-667-1308

    Another update on MY car -


    I rotated the tires/wheels last night (took more time than I had planned). I noticed as I was wheeling one of the front tires to the rear that I heard a rattle inside the tire. It appears there is some debri or small pepple loose in the inner tire area. Nothing big, but very small. Maybe that is causing some trouble? The tire holds air very well and no leaks or punctures I can find.


    So after I get everything torqued up, I take it for a long spin. Here are my impressions:


    1. The shimmy has changed a bit. It now happens at around 60 MPH instead of 55 MPH, and it is not as bad as it was.


    2. If I accelerate steadily through the range to 65-70 MPH, I don't notice a problem at all. When I "cruise" at the 60 MPH range I notice it, but it isn't as bad as it used to be.


    Unfortunately, I do way more driving at 60 MPH than at 55 MPH, so this is still a problem. Do you think, by making the problem change with a rotation has isolated the problem to the wheel/tires? They have been re-balanced a number of times over the years, but never "road force" balanced.


    I also notice that I am in need of an alignment. This was noticed earlier this spring. Should I take care of the alignment before or after I do a road force balance, which will help me identify any wheel/tire issues.


    Any other thoughts?


    Thanks,

    Troy

    I suggest you check the pinion angle.

    If it goes away under accellaration

    it could be because the pinion angle

    chages, i.e. the pinion is pointing too

    much downwards at cruising and move upwards

    during acceleration into the correct

    angle.

    Just a thought.

    /Bo

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