Ok about 3 weeks ago I said that I had a vibration that makes the whole car shake sometimes.It happens between 40-50 and then again between 65-75.Well I got about 3 responses and the all were the obvious...

1.Check Driveshaft....Did that and the mechanic said it was fine.
2.Check Tires....Spent 300 dollars on some new Firestone Firehawks.
3.Alignment....Did that a week ago and yet the vibration remains.
4.Wheel Balance....Did that and of course it didnt work either.
5.Back Shocks....Got some of those and of course it just keeps on vibrating.

Ok now it does something new though and it didnt start until after I got the alignment.Now ANYWHERE after 55 the whole car starts to shake and vibrate and I can hear this sound that sounds like a bowling ball rolling down an alley and in the drivers side floorboard you can feel something vibrating and on the passengers side you can feel it vibrate hard and it sounds like it may be coming from the right side of the car.Sometimes it vibrates softly and sometimes it vibrates HARD and sometimes it doesnt even do it at all.Now I love my car and I would love to get it fixed but im really tired of messing around with it and I think im just gonna sell it and buy this T/A I was looking at in the paper but before I do does anybody have any ideas on this?Oh yea by the way its a 85 Firebird S/E with a 350.Oh and I have bigger tires on the back than in the front...Would this have anything to do with it?

Thanks to anybody that helps.

 

Vibrations can be fun to find. (as I am sure you are well aware at this point.)

I am going to assume that the shop you took your car to for an alignment, had a clue of what they were doing....... So, we will assume (dangerous word, assume.....) that your front suspension is in good shape. You have also apparently eliminated some of the more common causes of vibration. So, we need to look at some of the less common problems.

First. Do you feel the vibration more thru the steering wheel, or thru the seat? or both?

Second. Have you checked your wheel/axle bearings? The sound you describe could be caused by bearings that are getting ready to fail. (this is no fun at all at 60+ miles an hour.........)

Third. when you had your new tires put on, I assume they balanced them, but, did they check the runout on your wheels? (possible bent rim.......) also, make sure, if you have factory wheels, that they did not mix up front and rear wheels..... They have different offsets, and if they have one of each on either end of the car, this can cause some truly bizarre handling problems.

Fourth. How did the mechanic check your driveshaft? If you want to isolate this particular peice, run your car up to a speed where it vibrates rather nicely, and let off the gas. If the vibration goes away when you take your foot off the pedal, then you prolly have u-joint problems. If it is still there, then you need to continue look elsewhere.

Fifth. How are your front struts?????? Upper strut mounts? Strut bearings?

Tire size difference between the front and back should not make any difference at all. Provided both tires are the same size side to side (front or rear)

See if any of this helps, if not, let me know what ya find, and we can go a little further........ I am thinking you should be able to get this.

Have fun.

 

Let's start out with the extreme basic question. Is the vibe at wheel speed, or is it at driveline speed?

If it's at wheel speed things to check would include: bent wheel, bad tire (new tires, especially cheap ones like Firestones, aren't guaranteed to be perfect), bent axle, loose front end component, incorrect alignment (again, the act of paying someone to align the car does not magically guarantee that it's set correctly), front wheel bearing, rear axle bearing.

If it's at drive line speed: drive shaft, U-joints, pinion bearings, transmission extension housing bushing, driveshaft yoke where it plugs into the ext hsg bushing.

It's fairly easy to find a bent wheel or axle. All you have to do is put the rear end of the car on jack stands (with the stands under the rear end housing!); start the car up; put it in gear; and get out and look at the rear wheels and see if either of them is wobbling. You should be able to see a bad tire the same way. If one wobbles and the other doesn't, swap them. If the same wheel wobbles on the other side, it's bent. If the same side wobbles with a wheel that didn't wobble when it was on the other side, it's a bent axle. If neither one wobbles, swap tires front to rear and repeat the test.

Once you've established that the wheels, tires, and axles are all straight and round and true, then you've eliminated most of the possible causes related to wheels.

Driveline is a bit tougher to diagnose. First thing would be to replace the U-joints, that's cheap and easy. If you get a NEW (not used) yoke at the same time, the labor to change it is basically free because it's apart anyway, you just set the old one aside and install the new front U-joint into the new yoke instead of the old one. Alot of trans shops have the tool for changing out the ext hsg bushing without taking the trans apart; I had mine done a couple of months ago, it was $30 parts & labor. Call around first and find somebody that has the tool. If none of those things changes it, then it's the pinion bearings, which will require a teardown & rebuild (or replacement) of the rear end.

If your mechanic didn't take the driveshaft out and send it to a balance shop, then he didn't check it. He just looked at it and thought it looked OK. Not adequate.

I can almost guarantee you that no mechanic is ever going to find this if you just take it to them and tell them to find & fix a vibe, and that you will go bankrupt paying somebody by the hour to troubleshoot it for you. You're going to have to get after it yourself.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Sounds almost like the vibration I got when I installed a new tranny mount. Vibrations in a couple of different rpm windows drove me up the wall. Got a new stock rubber one and problem went away.

 

I had a vibration around 55 to 65 for YEARS. Couldn't get rid of it until I decided to get rid of a bent wheel rim, which most people told me was NOT my problem. Got rid of the bent rim (got a used good rim) and no more vibration... good luck....

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88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

sell it.