Hello

My 66 has developed a vibration/wobble from the rear wheels.

With the rear of the car jacked off the ground there is no play to be found in either of the rear wheels and they feel pretty smooth when you turn them by hand. when you fire the car up and spin them up the right side does not run true. the left side also does not run true but is better than the right side. you can begin to feel a vibration at about 40+ mph with car off ground.

When the car is on the road at 40 it is smooth and all four wheels are running true (had wing man to observe)

At 70 mph both front wheels are perfectly smooth as they were at 40 however the right rear bounces about 1/4" or better up and down and is quite easy to spot as being "much worse than the 2 fronts which are totally smooth"
The left rear is better than the right rear but still not as good as the fronts.

I think its time to replace some rear end stuff. I don't think its a wheel problem as all 4 ties have been replaced (200 mi ago) and they all balanced out fine.

What do you guys think ,the car has 156,000 on it.

Gun

 

is running the car with wheels off the ground good for it? I know with RC cars, it's a quick way to hurt your car, but never thought about it with a real car.

Does it make any noise?

 

Gun, is your car still running the 8" diff?
Sounds like abuckled rim or bad balance on that tyre (weight fallenoff?). Could also bea bent axle or a bad bearing (least likely).

I'd try a different rim on that corner and do the test again.
depends how many miles you end up doing before you find the cause, but driveline harmonics are wierd things. Mine had a bent axle, the vibration of which ended up killing the u-joints in the driveshaft. Fixed the axle, but the new u-joints packed up about a week later?!!?!?

 

It sounds okay, It could be a bent wheel but wouldn't that show up during a wheel balance? All 4 wheels balanced fine.

Im going to take it to an drive line shop but wanted to see what you guys thought first.

I dont know if its an 8" diff its a 66 v8.

It doesnt make any noise.

Gun

 

Just had the same problem on my wifes car, it was one of the tires. There new with 10000 miles on them and a cord broke. Had them balanced and the guy said they were fine, took it down the road, still a vibration. Had the bad one replaced and all is good....Hope this helps.

 

+1 LCC...could also be a tyre.

You can get a balance done and have a weight fall off on the way home. You can still balance a bent rim too, so need a guy who gives a **** to be looking for an issue. hard to get good help these days!

Swap the wheel first before you spend money at the shop.
If that fixes it you have narrowed it down to the rim, tyre or balance without spending a cent. Will save you heaps.

If it doesnt fix it, then bent axle is looking most likely. I'm betting your car is still an 8" diff. You can bend or twist an axle by hitting a curb too hard or simply too much torque for the axle.

Just to give you an idea...
if you jack the car a little off the ground, put a solidobject next to the wheel. let the car idle in gear so you can see what is happening.

1) if the rim is moving in and out relative to your immovable object, then bent rim or axle.
2) if nothing visible at low speed, then most likely a tyre issue. When you run it up to speed it will be going more up and down rather than in and out relative to your immovable object. Thisis most likely balance or tyre itself.

was it doing this before you replaced the tyres??

 

With the car off the ground at low speed (10mph indicated) the right rear has visible up and down motion. when you view the very outermost edge of the wheel as a reference. its more noticeable at 60 (indicated) The left side hassome up anddown motion too, less than the right but still enough to raise concern.(both wheels are bent?)

I cant say if it was doing this before the tire change or not. I remember thinking this seems a rougher ride than normal. I was escorting my dad home because he had just purchased a new used car and he wanted to make sure it didn't have any issues on the way home. I pulled up along side him and he noticed the rear wheel issue. He told me when we got home and so we started to troubleshoot the problem.

Thanks

Gun

 

its hard to tell from your sig pic...are they steel rims, single piece alloys or 2/3 piece alloys?

I hate these problems!!!

It is certainly sounding like an axle, but can you borrow a set of rims from someone or swap your fronts to rule out the rims and tyres?

 

They are single piece alloy.

I could swap the front and place it on the rear and run it on the jackstands as the front are 60 series and back are 70 but we only need to watch the rim. If its smooth then we know its the wheel.

If itdoes the same thing then its an axle i guess.

Ill probably try that and see what happens.

Thanks for the advice.

Gun

 

Okay I played around with a few things that you guys suggested.

First I took the car to a wheel/tire shop and told them the issue they said they would balance and check the wheel and tires to see if they were out of balance. They would also check the wheels for runout.
Some weights had fallen off and they made it right again they also said there was no runout on either of the back wheels.

Second I jack the rear of the car up and built a indicator out of a few clamps a brick and a tire pressure gauge and a 3ft level. (works good enough) I placed the indicator on the edge of the wheel farthest out from the center. and spun it by hand, I could see the wheel pull away from the indicator and then back. I measured .025 or better gap. You could see it with the naked eye pretty easy. (this was right rear the left was less)

I do the same on the front wheel at the same distance out and cannot see any runout even with the indicator in place (maybe .002 at the most)

third I swap the front wheel and place it on the rear. Spin by hand and again a whole grip of runout just as bad as before.

Finally I remove the brake drum from the rear and measure off the top of the axle face (the thing with the lug studs in it)The indicator was placed on the top (imagine a quarter/25 cent piece. The edge with the ridges would be where i measured from if that makes sense) I could see the edge pull away from the indicator I used a business card that measured .011 thick. At point A the indicator would touch and there was no gap at point B the card would slide through with no effort probably a .014 gap

So I guess its an axle then right?

Gun