Mustang Vibration Problem

Wayne Maybury · #1 (**permalink**) 08-04-2010, 08:14 AM

I have a fully restored '66 Mustang 289 (slightly modified), automatic, PS, PB, etc. It is a nice daily driver but it has a vibration that I have not been able to track down until now. The steering wheel doesn't vibrate so it must be coming from the rear of the car.

I had the wheels balanced a couple of times, I had the drive shaft balanced, and I changed both U joints. The vibration is at it's worst at just around 65 mph, especially if I do not press hard or remove my foot totally from the gas pedal (that is I gently press and release the pressure on the pedal). I haven't gone over 70 with it due to this vibration so I cannot say if gets worse or is less at higher speeds.

I have Cragar SS wheels so the suspicion was that the wheels are causing the vibration due to the oval wheel stud holes. I decided to try removing the rear wheels one at a time and moving them by one stud to see if this changes anything. While doing that I noticed that the left rear wheel bearing appears to have some movement or slack in it. I can move the left tire and wheel between an 1/8" and a 1/4" while the right wheel tire does not move at all.

While there is no apparant wheel bearing noise, I do not like this slack so I am going to order 2 new wheel bearings and seals. Would this cause a vibration at highway speeds? Any other ideas? I love my Cragar SS wheels so please don't tell me to get rid of them.

Wayne

95CobraR · #2 (**permalink**) 08-04-2010, 10:50 AM

I've owned a few 1965-1966 Mustangs over the years.

I don't see it being a rear wheel bearing, but you should replace them. You can pull them out without removing the brakes or draining the diff fluid. There is a tool, but I made one with a bolt and some washers.

Just grease them up and carefully tap the new bearing back in.

Did you try moving the rear wheels to the front (and vice versa) to be sure it isn't the wheel or tire? I've seen on several occasions when the tire balance machine was not calibrated properly.

Did you check the pinion on the diff? That bearing can fail and cause a vibration.

I'd check the main shaft on the auto transmission if all else fails. I've never had an auto, but the rear case can fail on a toploader. It will cause a big vibration.

Good luck.

Wayne Maybury · #3 (**permalink**) 08-04-2010, 02:09 PM

95R

Thanks for the comments.

The rear tires are bigger than the front so it would be difficult to move them. I have switched them side-to-side with no improvement. I have considered borrowing 4 tires and wheels form a friend to see if that helps.

The pinion bearings are new so that is not the problem.

A friend also suggested the tranny may be the problem so I took the car up to the point of vibration and put it in neutral to see if the vibration would stop... no change so it isn't the transmission.

One other possibility is the front U joint. It was difficult to get the clips in so this joint has a bit of stiffness or resistance. I thought that it would "work" itself in but that may not have loosened up.

I plan on removing an axle tonight to measure the bearing. Mustangs Unlimited have more than one size of rear bearing for the 66. Better to measure first then order.

The bearings are relatively cheap so I am going to change them to see what happens especially since one has some play which can't be good.

Wayne

Rick Parker · #4 (**permalink**) 08-04-2010, 04:55 PM

The rear bearing should not have any vetical or front to back slack in it. It is a press fit on the axle shaft and is held in the axle tube by a retainers with 4 bolts or possibly the brake backing plate. The bearing is readily available at any auto parts store or bearing supply house and R&R'd by any competant machine shop or auto repair shop with a hydraulic press. Good idea to replace both sides at the same time. The number on the bearing is pretty universal.

Wayne Maybury · #5 (**permalink**) 08-05-2010, 06:44 AM

Rick

I pulled the axle last night and the outer race can be moved quite a bit so this bearing is toast. I forgot to look for the part number before putting the axle back in but I did measure it. I will look for it locally based on the measurements and only order it from Mustangs Unlimited if I can't find it here.
I find it strange that this bearing has this much play but doesn't seem to make any noise.

Wayne

Z-linkCobra · #6 (**permalink**) 08-06-2010, 11:02 AM

You need to recheck your tranny. Just because you put it in neutral doesnt mean the output shaft quit turning...lol. Generaly speaking if you have a vibration in the " float range" where your not accelerating or decelerating its in the drive shaft or some part of that assembly. It could be pinoin,yoke,slip tube,u joint...66 has the 8" rearend correct? Could be the rear support bearing for the pinoin.

If you bought a new drive shaft for this car make sure its not too short or too long for that matter. Too short will cause a hell of a vibration...too long is really hard on parts.

just thinking outloud.

Wayne Maybury · #7 (**permalink**) 08-09-2010, 06:59 AM

Z

Thanks for the comments. I never really suspected the transmission as there is no vibration in the floor shifter at all. I know that it is bolted to the floor pan but if the transmission was at fault, I would think that I would feel some vibration on the shifter. I jacked up the rear end of the car and put 2 good size jack stands under the differential so that the car was well supported. I stated it up and ran it up to 70 mph.... no vibration. I found that to be very strange. I looked at the tires and wheels turning at 5 or 10 mph and there did not appear to be any up-and-down movement at all. One wheel did have a slight side-to-side movement of about 1/8". I plan on taking that wheel to a place that can straighten it out. The tires are new Goodyears.

I got the new wheel bearings on Friday but I didn't have a chance to change them yet. I know that a wheel bearing will normally not cause a vibration but since one is finished, I decided to change them before going any further. As I said earlier, the new front U-joint doesn't move as freely as it should. The ears on the drive shaft seem to be a couple of thou too close to each other. After changing the wheel bearings, the next step will be to remove the front U-joint and see if I can free it up.

A good friend of mine has told me several times that the Cragar SS wheels with the oval stud openings are the problem. I hope he is wrong as I really like those wheels.

Wayne

zrayr · #8 (**permalink**) 08-09-2010, 04:23 PM

here are bearings you need:

Rock auto: timken sealed bearing with lock ring RW207CCRA $16.95 timken seal
51322 $10.97

Z. Ray

Wayne Maybury · #9 (**permalink**) 08-10-2010, 08:03 AM

RW 207CCRA is what I bought.

I replaced the left bearing last night and took the car out for a quick spin. I don't know if it is just wishful thinking but the vibration seemed to be almost totally eliminated. I took it up to 75 mph and it was smooth but there was still a slight vibration at 64 to 66 mph.

Wayne

Joe Wicked · #10 (**permalink**) 08-10-2010, 08:08 AM

Wayne, based on that, I would suspect that whatever is the source of the vibration caused the bearing to go bad. I would keep troubleshooting, before the new set of bearings is worn out.

Wayne Maybury · #11 (**permalink**) 08-10-2010, 09:21 AM

Joe, this bearing is 44 years old. I don't think I will be around in 44 more years.

Good point however and I will keep looking. I also want to take the car out for a proper test drive to see if the vibration really has been reduced or if I was just hoping it was gone last night.

Wayne

Joe Wicked · #12 (**permalink**) 08-10-2010, 10:35 AM

LOL, I didn't realize it was the original bearing. That definitely changes things.

Wayne Maybury · #13 (**permalink**) 08-10-2010, 11:49 AM

Joe, I only bought this car 6 years ago and I have virtually none of the history. However the bearing lock ring had a shoulder on it and I was told that this meant that it was probably the original bearing or at least a very old bearing. The present day locks don't have this shoulder on them. You still have a valid point. I got 2 bearings and I will change the other one when I have a chance, probably this winter.

Wayne

Anders71 · #14 (**permalink**) 06-05-2015, 04:53 PM

Hello Wayne ..
Just Wondering how did it go with the vibrations..
I have unfortnetly the same problem with my Mustang 66.
would be happy for some input thx / Anders

95CobraR · #15 (**permalink**) 06-05-2015, 10:23 PM

Wow,
I got this from 5 years ago. My signature is so old that I can't change it.

Wayne had a rear vibration. Is your vibration on the front or rear?

My car is good at 150 Mph.

Ron61 · #16 (**permalink**) 06-06-2015, 03:20 AM

Wayne,

I hope that the new bearings will eliminate the vibration completely, but if they don't and you think maybe it is the wheels, do you have a couple on another car that has the right bolt pattern and will fit that you could just switch for a test drive and see if that helps. If it doesn't then you can eliminate the wheels which you like and want to keep.

Ron