This one has me stumped.

Its a deep, cyclic, wooooooooo, woo, wooooooooooo type. Its not a knock. Sounds like something may be resonating. It comes in and out smoothly. It comes on at 50, peaks at 55, disappears by 60. At 55 its very loud, will cover the wind noise if window is open. I think it may be speed/load related and not rpm related but its hard to experiment since it occurs over such a narrow margin. I thought I heard it at a lower speed, maybe around 40 but that was barely audible and may of been something else.

I don't feel it in the steering wheel. Found my front wheel bearings were worn, replaced, and its still there no different. Come to think of it the sound was always there but lots quieter. I thought it was some sort of exhaust resonance in the muffler so I never payed attention to it, now suddenly it becomes this loud.

I'm fairly confident its not in the front if I don't feel it in the steering wheel. I have a spare freshly built 8 3/4" pumpkin so I may swap that in. Anything else I should pay particular attention to that rings a bell?[/quote]

Do you have power steering?

if so, that's my quess

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Negative, manual steering stock box.

My guess is a u-joint or driveshaft-related problem. Did you change anything in the rear susp or driveshaft/axle recently?

Lou

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Home of Slant6-powered fun machines since 1988

Not recently, no. When I moved to the 8 3/4" from the stock 7 1/4" (maybe 30k miles ago?) I had the driveshaft shortend and balanced. I'll see if theres any wobble in the joints next time I'm under it.

Transmission output shaft bearings/bushing.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Rear axle pinion angle.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I want to get the rear tires in the air and run it to see if I notice anything, probe around with a scope.

Dan - if it was an angle issue, won't it show up instantly when it was changed? Or maybe if the angle was off it took a while but wore the transmission / pinion bearing prematurely.

You'd think, but sometimes things settle or???. I had this problem (WUMMMM...WUMMMM...WUMMM... type vibration at certain speeds) starting about 20k miles after the 8¾" swap into my '65.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

What was the fix in your case?

Using selective wedges to correct the pinion angle. It was way too far up to start out with. I didn't twig to the cause of the problem until, in the middle of a long road trip, I suddenly realised the noise had gone. The car was very heavily loaded, and the floor pan was pushing down on the rear axle nose via the pinion snubber. How did I figure out that was nudging the pinion nose down just enough to get rid of the noise? Well, I hadn't tightened the pinion snubber bolts properly, so they worked loose. I heard a "Whack...WhackflipkerCHUNK!" from the back of the car, and looked in the rearview to see my pinion snubber spinning and flying into the ditch behind me, simultaneously noticing that the "WHUMMMM...WHUMMMM...WHUMMM..." noise had suddenly come back.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Lemme see.......Dan under heavily loaded car trying to bolt halfborked snubber back on pinion while the factory bumper jack sways in the breeze. Not a holiday by any definition.

wwwwwhuuuuummmmmm indeed!

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Two things come to mind. Im not trying to be a smart asz but have you checked the diffentrial fluid and it could be a rear wheel bearing starting to belly up. If the fulid is low could also be a pinion bearing Thanks
Ron Parker









Jaggers Fabrication Slanted Attitude Dart

Definately check the rear pinion angle and u-joints. I've had a very similar experience to what Dan described, too.

Hell, with low fluid, it could be the ring+pinion.