'67 Driveline noise - wheel bearrngs or rear end?

[Alexander D.]

I'd like your opinions on the possible source of a driveline noise in my '67 coupe. Here's what I can tell you about the noise:

1. The noise has been intermittent for the past couple of years, but has become more frequent lately.
2. It 'seems' to be coming from the rear of the car. But that might be an illusion caused by the fact that it mostly happens at higher speeds and the noise gets carried backwards?
3. It is a humming gear 'whine' type noise, mostly lower frequency, not high pitched. The noise gets louder as speed increases. It's barely noticeable at 30mph, but as one gets up above 60mph it sets up a 'booming' type noise, clearly audible.
4. The noise does not seem affected by engine RPM. When I pop the car into neutral at speed, it has no effect on the noise.
5. As mentioned, the noise has come and gone. Once it comes, it remains until I park the car. It appears that "maybe" it's related to operating temperature because often there is no noise until after I've been driving the car for a while.
6. The noise will momentarily disappear if I swerve LEFT while tracking down the highway. If I swerve RIGHT, the noise gets a bit louder.
7. I've stopped the car after a long run when the noise is present and used my IR gun to take the temperature of the wheels. Nothing exceptional here, all are within 10 deg. F. of each other.

So, what's your best guess of what is causing this noise? Wheel bearings? Or rear-end? How difficult is it to replace rear wheel bearings on the C2? Could it be the spindle bearings?


All ideas/experiences much appreciated,


Alex
# 61370

[Michael W.]

Re: '67 Driveline noise - wheel bearrngs or rear end?

when's the last time the rear wheel bearings were serviced?

[Richard G.]

Re: '67 Driveline noise - wheel bearrngs or rear end?

After a short drive with a heat gun (or your hand but be careful). Check both outer spindle temperature’s and note the differential.
I have seen where the failed bearings make very little noise when the interference fit is gone. Not yours but included as a cautionary note.
Sometimes a defective bearing is difficult to identify as defective by how much it moves when pried upon. The issue is the drive-line is also a suspension component and has a lot of preload on it.
When the car jacked up the wheel bearing assemble is pre-loaded by the drive-line even more so than when sitting on flat its wheels.
Defective wheel bearings/axles can fail and leave the Corvette uncontrollable or damage the fender when they fail completely. For these reasons the issue should be diagnosed as something other than the wheel bearings before it is driven far or at speed. Another method to check for defective spindle bearings is to remove the axle shaft from the spindle flange and then wiggle the tire. This can be done with the car jacked up as this removes the preloading. This will give you the opportunity to eliminate the U-Joints as a source of the noise, because you can now move the joints and check for looseness and notching and get real axial measurements. Axial play should be under .011.
While you are under the car check the differential oil. Suck a little fluid out and look at the color and for contamination. My bet is after completing these inspections you will have a good idea where you issue is located.
Rick

[Mark E.]

Re: '67 Driveline noise - wheel bearrngs or rear end?

Good advice from Rick.

If bad enough, wheel bearing runout can be detected by feel without disassembling the axles. Significant play is more common than you'd think.

To Michael's point, if the rear suspension/drivetrain has significant miles, the long term fix is to rebuild the entire system- bearings, bushings, all six joints. The idea is to tear into it once.

[Alexander D.]

Re: '67 Driveline noise - wheel bearrngs or rear end?

SOLVED - The shop called and reports my problem is a worn-out front wheel bearing.

The left front bearing is going bad, and the right isn't far behind. So, I'll have both front wheel bearings replaced.

I'm glad it didn't turn out to be the spindle bearings or the differential, as fixing those would be rather more expensive, from what I hear.

I should be back on the road tomorrow!

Thanks everyone for your thoughts and tips.

Alex
# 61370