67 rear end noise - help!

[Alexander D.]

I'm puzzled by a noise coming from the rear of my '67 coupe.

Shortly after I got the car 3 years ago I noticed a noise coming from the rear that would appear and then strangely be gone the next time I drove the car. Now, the noise seems to be present a bit more often. This noise, when present, is more noticeable at speeds above 60mph when cruising on the highway.

I'd describe it as a "howling" or "whining" noise. It sets up inside the car as a kind of "booming" noise. No, not super loud, but definitely noticeable. It also 'seems' to have a mechanical 'whine' element, but that's maybe my imagination... As mentioned, its more noticeable at higher speeds on the highway. It is not connected to the engine speed, and seems to be coming from the rear portion of the car.

Oh, and sometimes when I go over a bump or undulation on the highway, the noise seems to momentarily go away, only to return when the car levels out.

As mentioned, the noise isn't constant. Once it sets up, it will usually persist for the duration of a cruise. But the next time I drive the car the noise might be absent entirely.

In searching this forum for "rear end noise" or "howling noise" the following were mentioned: carrier bearings, or rear spindle (bearings I presume?). If that's the case, would such bearing failures cause the noise to come and go? I would think if a bearing was shot then the noise would be constant, no?

Could there be something else vibrating back there to cause the howling/whining noise? Rear tire carrier? Exhaust? I have the original spare wheel & tire, never used, that's been riding in the carrier for 50 years now. Maybe I'll take it out and see if it makes a difference - but my luck is I'll have a flat tire and wish I had the spare with me !!!

Should i wait until the noise gets worse?

Any hints/clues to the source of my mystery noise are appreciated!

Thanks,
Alex
NCRS# 61370

[Timothy B.]

Re: 67 rear end noise - help!

I would look for a bad wheel bearing possibly in the front. if you drive the car when it's making the noise and turn the wheel left or right does it go away for a second.

[Gary R.]

Re: 67 rear end noise - help!

Does the noise change when you let off the gas? Get it between 40-60 mph in 4th gear.

You're correct bearings that are bad are not going to sound any better. Was any work done to the diff or arms that you know of?

You can check the outer axle bearings for play in the axles but checking the diff bearings is different. You can see if there is any play in the pinion yoke.

[Richard G.]

Re: 67 rear end noise - help!

A friend of mine had a leaking differential cover, it was cracked and leaked.
I assisted him in the R&R.
While it was out I told him we should do the wheel bearings. He said why? No noise or other issues.

Because "it don't get any easier". I said. I convinced him to look at them.
After it was apart we found one badly deteriorated axle shaft. It was undersized by over 1/8" at the bearing fit.
No better method of keeping the rear fender on a old Corvette that maintaining the axle bearings.
Especially if you have no history on the car.

Rick Geier

[Gerard F.]

Re: 67 rear end noise - help!

Alex,

Could be a rear wheel bearing noise. Basic test is to jack up the rear, push and pull the rear wheel, top and bottom, and see if it moves excessively.

You don't want to wind up like my 67 (in 2008):



The attachment below is an article from the Summer 2009 Restorer about my problem and fix

[Richard G.]

Re: 67 rear end noise - help!

Bearing inspection is all but impossible when the axle is at the lower limit of the spring travel.
i suggest jacking on the trailing arm just enough to raise the tire off the road.
Then check the axial and radial play of the axle. Preferable with a dial indicator.
If done any other way the bearing will be pre-loaded by the drive axle.
Remember as the trailing arm is lowered it also moves closer in because the finite length of the drive axle.
The pre-loading can be significant and will not allow any axial play to be measured unless the wheel is in the same position as it is when the Corvette is on the payment. If you are forced to measure axial play with the trailing arm in the lower position I suggest removing the drive axle first. This will give the most accurate measurement.
If an axle shaft is undersized the bearing inner race can then act like a sleeve bearing and may not even sound bad.
The races have to have significant spalling to feel any defects. This means you have to catch the issue in a very small window.
As in after the defects can be felt and before the bearing fails.
Likely this is why this subject is scrutinized time and time again on the forum.
If you are concerned about your rear wheel bearing do a correct inspection or better yet pull them apart and do a complete inspection.

Rick

[Gary R.]

Re: 67 rear end noise - help!

Rick gave very good direction. Typically if the outer axle bearings are making noise you will feel it. With the load off the axle, either with the 1/2 shaft out or the car up in the air if you grab a wheel stud and can move it in/out by hand you will have too much endplay in them, the dial indicator is the best method of course but many guys don't have one. Now at 003 endplay I can feel movement in the bearings. The spec is 001-008" but the closer to 001 the better. When I set them up I am not even concerned with that spec. I set them up for -0- lateral play and once that is achieved the endplay will be in the 0015 range. With HP axles the bearings are setup for a preload.

Another consideration is age. I have taken apart several mint arms over the years. The last being two 1966 arms off low mileage one owner, always garaged cars. They looked brand new but once I got them apart there was no grease left on them, nothing at all. They would have failed in use very quickly. Keep in mind you can not expect to tear them down, relube them and assemble them like front bearings. If you disassemble them you are committed to replacing and dialing the bearings.

If you have the 1/2 shafts out, you can also check the endplay in the inner axles. With a factory built or common vendor rebuilt diff you can expect to see between 010-050" endplay, some even more. Assuming your car has a 1967 diff in it and not a 70's replacement the axles are usually still good, even with 100k miles on them. The excessive endplay is caused by 3 things. I consider endplay over 010 excessive but many cars are on the road with a lot more. They could be causing a metal on metal noise if the axle is worn but from what you describe I would be looking at bearings or worn gears.

If you have questions or want to go over the checks let me know

[Michael L.]

Re: 67 rear end noise - help!

Agree with others that this could be an axle bearing. The noise from these can be very variable and can depend on how far you have driven and at what speed because the noise may only occur after the bearings have heated up some. Even the weather can affect these as driving on rainy days (heaven forbid!) can help keep the bearing a little cooler and prevent the noise. I agree with others that an ounce of prevention certainly applies here and I would commit to a complete disassembly and full inspection. The progression in the frequency of the noise indicates the problem is getting worse and much better to address it before a catastrophe.

Mike