claudeC1'60

I have a C1 1960.
The noise started when cruising at about 60 mph, suddenly I had a whine like a trumpet sound coming from under the central console, not a constant noise but only from time to time. I reduced my speed at 40, the noise disappeared, then came back. Reduced speed again to 30, noise disappeared and came back again.
Now I have no noise under 25 mph, and a constant growl above that speed.
Tried change gear, the noise is still there, depressed the clutch pedal, no change, coasting in neutral with engine stopped, no change.
The gears seem to work smoothly, I checked the oil OK in the transmission. I checked again from where this whine is coming from, it's definitely from underneath the central console, not from the rear end or rear wheels.
It is speed and not engine related, but the whine pitch (or tone) is pretty constant whatever the driving speed is.
Any ideas ?

corvetteed

Speedometer cable?

Canuck62

I would check u joints,,, they usually produce a nice growl when going bad

Frankie the Fink

Check U-joints (as noted); check for shifter rattle; look at how the exhaust goes through the frame (no rubbing) and then look at those left/right splash shields to make sure they aren't loose. Did you engage/dis-engage the clutch and see if the noise changed/disappeared ?

If you can get the car in the air and safely run it briefly you might spot the issue from underneath too..

Black 03 Z06

You are not missing a dog are you? Agree on the U Joints, they can and do make some odd noises.

Good luck.

Roger Walling

Did you say the whine went away after your wife got out of the car?

6D2148

Noise travels check the rear

claudeC1'60

Wow, a lot of ideas there ! Thanks !
BUT :
- U joints are 6 months old (can they be shot already ?)
- splash shields, shifter, rear axle have just been refurbished
- exhaust is new and not touching frame
- keeps on whining whatever the clutch is engaged or not
AND
- wife, cats and dog were away...
Sooooo
- Next thing to do is jack the car up and recheck all that, and disconnect the speedo cable to see

I did a quick run with a cold car and no noise so far, so it could also be temperature related

I was thinking also of the geabox extension rear bushing. How is it lubricated BTW ?

GTOguy

Noise can telegraph from the rear end up the driveshaft. Could be a lot of things, but I would check the rear wheel bearings as well. If you could run it up on a hoist, you might be able to tell if it goes away with no load on the suspension/drivetrain. Common causes for howl or whine are ring and pinion issues or bearing issues. Ring and pinion tend to be noisy on de-cel or accel, but not at coast. Good luck.

Frankie the Fink

GTOGuy is spot on, I happen to know he's a mechanic.

If you checked all the things you said then I would start looking more rearward as advised above. Wheel bearings typically growl or rumble; a worn out rear end will whine. A bad speedometer cable will usually tick.

Check the diffy and tranny fluid too - for consistency, contamination and proper amount.

The mixed up symptoms are a little strange.... You need some means to isolate the issue.

wraplock

just to be clear are you saying the noise is present while coasting with the engine off and the clutch pedal depressed?

Don

Auto Gear

Here is what I would do:
Pull driveshaft.
Separate slip yoke from driveshaft.
Inspect U-Joints at both ends; inspect the yoke for cracking, crowning or an overly polished appearance, or scoring.
The rear extension bushing is lubed mostly by splash and suction by the in-out movement of the yoke

If the U-joints arent bad; stick the yoke in the back of the transmission and carefully run the car at the RPM you need to generate the noise. If the noise is still there, disconnect the shifter linkage and repeat the test.

I suspect that running the car without the D/shaft will remove the noise

claudeC1'60

I just come back from another long test drive and guess what ? The noise is gone ! Everything runs as it should, nothing special under the car, it looks like there never was a problem (until next time ?).
So this is another mystery yet to be solved.
I will soon change the diff gear from 3.7 to 3.36 and take the opportunity to check the driveshaft anyway like Auto Gear advised.
Thanks again for your valuable advise

Frankie the Fink

Just keep an eye on things for a while. I've had crazy stuff like that happen; got a lump of wet asphalt on the inside of a wheel that made the tires seem square for a while then apparently fell off in the garage !? A funky aftermarket cruise control in a 66 Mustang that had sensor weights on the driveshaft secured by a radiator hose screw clamp. The weight slid around and you could feel the vibration believe it or not. That whole POS setup went right in the trash can.

claudeC1'60

Frankie, talking about drive shaft when we realize it rotates at same speed as the engine in 4th gear, I wonder why it is not balanced to avoid vibrations. Maybe its relatively small diameter does not generate a great centrifugal force ?
And for your sensor weights around the shaft, this was definitely not a good idea...

Frankie the Fink

Driveshafts ARE balanced; you'll sometimes see weights welded on them or drilled out spots to eliminate vibrations.

I've had several balanced over the years...

claudeC1'60

You learn something every day

MasterDave

Sounds like you have had some work done recently. I would look for loose/missing bolts. A loose tranny bolt could vibrate and 'growl'. Once it has fallen out, no growl.

claudeC1'60

Powershift

However, C2 HALFSHAFTS are not factory balanced due to their slower rotational speed (rear gear ratio).

FWIW……….

Larry