Road Noise

[ChrisM]

My '63 Avanti is progressing towards being fun to drive. I just replaced the 20 year old tires, tread like new, but weren't very round anymore. Lots of vibration and noise at 50 and up. The vibration is gone, but a lot of noise remains. There is a loud cycling droning noise and a  light slapping noise above 55-60. The drone sounds like exhaust or engine. The slapping is like there is something stuck on a tire. Both disappear  if I push in the clutch or put it in neutral. Where should I start next?

Thanks, Chris

[mfg]

The exhaust system has enough clearance?....Especially through the "X" member?

[Rob Dudley]

You need to narrow down where the noises are coming from. Can you get the noise by just revving the engine? It could be a bearing in either the rear end or transmission. It could also be a burned out muffler. Does it seem worse going around a corner?  Lots of questions are left. 

I have R3858.

Rob

[ChrisM]

15 hours ago, mfg said:

The exhaust system has enough clearance?....Especially through the "X" member?

I did a scan of the undercarriage when the tires were were going on. Nothing popped out, I will get it on jackstands and take a closer look. Thanks.

[ChrisM]

7 hours ago, Rob Dudley said:

You need to narrow down where the noises are coming from. Can you get the noise by just revving the engine? It could be a bearing in either the rear end or transmission. It could also be a burned out muffler. Does it seem worse going around a corner?  Lots of questions are left. 

I have R3858.

Rob

Wow 7 cars newer. Thanks, Rob, I'll check out the revving. With manual steering I don't take any corners fast enough to make any noises.

[PackardV8]

Quote

There is a loud cycling droning noise . . . sounds like exhaust.

Does your exhaust have a crossover H-pipe between the two sides?  This often quiets the drone.

Quote

 a  light slapping noise above 55-60.  The slapping is like there is something stuck on a tire. . . disappear  if I push in the clutch or put it in neutral.

OK, what isn't moving with the clutch depressed/trans in neutral that was moving in gear?  Clutch disc, pressure plate and transmission input shaft.  Those are unlikely sound sources.

Engine speed is more likely.  Driving above where the slapping appears, note RPM, go to neutral, maintain same engine RPM.  Does the sound continue?  If so, let the engine speed drop to idle.  Does the sound go away?  If so, look at belts, fan clutch (if so equipped) water pump bearing, power steering pump; everything which rotates at engine speed.

jack vines