Help with low growling/rumbling noise - 1955 CdV

[craig-o]

I hope someone can help me with a diagnosis.  The car is an unrestored 1955 CdV with 108,000 miles; the transmission was rebuilt at 103,000, the motor has never been torn down.  Recently, it has developed a low-level rumbling/growling noise that I have been unable to pinpoint.  When riding in the car, you can hear it (faintly) and you can feel it in the floor.  Here are my observations:
1.  It is proportional to road-speed, not engine speed.
2.  It does not change when accelerating, decelerating, maintaining speed, or coasting in neutral
3.  It does not change when cornering or braking[/li][/list]

I first tried re-packing the front wheel bearings; no change.
Next, I tried replacing the front wheel bearings; no change.
I lubed the universal joints in the driveshaft; no change
The gear oil in the differential has not been changed since I took ownership of the car in 1999; it's very possible that the differential oil has never been changed.  This will be my next attempt, but since it doesn't change when under load I'm sceptical that this is the source.

Any other ideas?

[Jon S]

My money is on the tires.  What kind of tires are on the car - Bias Ply or Radial?

[savemy67]

Craig,

This is a longshot.  Find a stretch of road that is relatively flat and straight.  Make sure there is no traffic in front of you.  Drive the car at a moderate speed (30 - 50 MPH).  Look in the rear-view mirror and find an object on which to focus.  While focusing on the object in the mirror, vary the speed of the car.  Does the object remain perfectly steady when viewed in the mirror?  If not, you may have an issue with the universal joints, driveshaft, or transmission mount.  As I say, this is a longshot, but an easy test.

As Jon said, the issue could be tire related.  Diagnosis at a distance is difficult at best.  Try the simple inexpensive things first - tire pressure equal?  Swap tires side to side one axle at a time - any change?  Exhaust system leak free?  Check clamps.  Any change?  You post indicated that no change in the noise occurred when cornering.  This might rule out rear wheel bearings but not necessarily as rear wheel bearing vibration is damped somewhat by the rear suspension bushings.  Listen at the axle housing near each rear wheel when it is off the ground and being rotated by hand.  Good luck and keep us updated.

Christopher Winter

[dplotkin]

Any other ideas?

Yes. Rear end bearings.

Rears in hobby cars or cars that have spent much of their lives sitting often end up with a diff full of condensate because the rear never gets hot enough to boil off the water. I've seen ring gears with one half covered in rust (the half not in the oil). The bearings get pitted and after enough use they fail and get noisier as you go along.

However, repacking worn out wheel bearings will do nothing for you. Shot bearings stay shot until replaced or until a wheel comes off. I assume you verified that the wheel bearings are in good shape.

Dan

[Jon S]

Dan -

He repacked the original wheel bearings and then replaced them so that variable should be gone. I'm still thinking it's a tire noise.

[35-709]

He repacked then replaced the front wheel bearings --- my money too is on the rear wheel bearings, which will have to be replaced.

[craig-o]

Thanks for all the replies.  I've been really hoping to get a friend who has at least as much experience with general car repair as I do to come for a ride and help me diagnose.  Unfortunately, our schedules haven't matched up for over a month6 weeks.  It's tough when we both still have to work for a living!

I'm going to suggest it's unlikely the tires.  They're less than 3 years old (about 1,200 miles, tops), radials.  Rotating them is a no-cost option that I will certainly try.  However, because I can't pinpoint where the noise is coming from, it might be hard to tell if anything's changed.  I'll try swapping side-to-side so they're each running in the opposite direction, that should exagerate if there's any irregular wear that I can't see from a visual examination.

I have resisted doing the rear wheel bearings, because of the oil seals and specialized pullers required - that I don't have.  If I read correctly, they're not packed with grease and are essentially a sealed bearing that is bathed in 90wt gear oil from the diff/axle.

Universal joints, I guess, are still suspect, as one or both may be bad, and pushing grease into them might not change the noise.

It looks like I'll be rotating tires, changing differential fluid and replacing universal joints.  If that doesn't do it, I guess I'll have no choice but to find someone who will replace the rear wheel bearings.

Since the transmission was rebuilt, I'll check to see if any of the transmission mounts were included on the repair invoice; but since it was done quite a while ago (like 2005), it's certainly possible, but unlikely that they aged that fast.  While she's up in the air for all the other work, I'll check the mounts, but I guess I would suspect that to be a noise that changed with load.

Thanks for confirming my suspicions.

Craig

[dplotkin]

Craig, it is not the wheel bearings I am thinking about, it is the rear end (pinion bearings).

Dan

[harry s]

Another way to check would be to raise the rear wheels, support with a good pair of jack stands. Have the car running in gear and listen from under the car with a stethoscope. I had a similar noise in a '79 Seville and was able to trace it to the left rear axle bearing. Operative word is to be careful. Good Luck,    Harry

[pjmiller099@gmail.com]

Does it have midshift


bearings on driveshaft?they make a rumble that's hard to find