My 73 Nova has developed an sound that shouldn’t be there. It started gradually and gained in frequency and length over a 2-3 day period. It’s now happening about 75% of the time under the right conditions.

Here is what I KNOW:
- the noise strikes me as rotational in origin
- the noise seems metallic, but also something else
- I’d describe it as a scratching squeak
- the noise ONLY occurs when the vehicle is in gear, moving, and under load
- the noise disappears when I let off the accelerator
- the noise disappears if I shift into neutral
- braking doesn’t seem to have any effect
- the noise is not present if I rev the engine while not moving, regardless if the transmission is in nuetral or Drive

Here is what I think:
- the noise seems to be coming from behind the driving position though I can’t be sure. Hard to pinpoint that when the noise only occurs while actually driving

Here is the Car:
- 1973 Nova 2dr hatchback
- zz4 350 that is about 15 years old, maybe 60k Miles
- turbo 350 trans, rebuilt once that I know off maybe 10-12 years ago
- 2.73 rear end
- drum brakes in rear

So my thought is it’s either the u joint where the driveline meets rear end or the rear end itself. Given the nature of the sound I don’t think it’s in the rear end...it sounds “exposed”, if that makes sense.

But I’m super far from being an expert.

Here is a video.

https://youtu.be/P4iy9W6ex8M

An unrelated question: can ya’ll hear the air hissing sound that ramps up asbthe car comes to a stop and when I revv it at the end? Does that sound like a vac leak?

Could it be that when you give it gas the engine torques on the mount and the fan is rubbing on something?

other than that, maybe its VVS. Vertical Video Syndrome.

Does it sound internal or external? One KT my techs has a nova, I'll show him the video

have you inspected the drive line yet?

quote:

Originally posted by pbramlett:
Could it be that when you give it gas the engine torques on the mount and the fan is rubbing on something?

other than that, maybe its VVS. Vertical Video Syndrome.

It does resemble the sound of a metal blade hitting a plastic shroud but I’m nearly certain the noise is coming from behind the drivers position.

quote:

Originally posted by cmr076:
Does it sound internal or external? One KT my techs has a nova, I'll show him the video

External if I had to guess.

quote:

Originally posted by ScorpionBoy:
have you inspected the drive line yet?

No. I’ll try and do that now but I don’t really know what I’m looking for. Unless it’s super obvious. I mean, I know what the driveline is but I’m not sure I’d be able to spot a problem, depending on the problem.

i would take a flashlight and look for any bare metal for starters. I agree it sounds like something is spinning around and rubbing. pramblett might be onto something. are your motor mounts warn out?

I hear a couple of tics when you stopped and rev'd the engine.

Check for an exhaust leak.

Sounds like a loose exhaust heat shield rubbing on the driveshaft.

How are your motor mounts?

Also, check your driveshaft and exhaust for any play or shiny spots that look like they might have started rubbing on something they shouldn't be rubbing on.

Sounds almost exactly like my '85 K5 Blazer did when the exhaust flanges let go before the cats.

I'd look for hanging pipes and/ or soot/ scorch marks along them.

Did you use non-metallic flange gaskets? Welded exhaust? Headers loose at head?

It could also be a weak bendix spring on the starter that is allowing the spur gear to contact the flywheel. when it warps under load.

quote:

Sounds like a loose exhaust heat shield rubbing on the driveshaft.

Yea but the driveshaft is still spinning when he takes his foot off the gas.

If it's not in the engine bay and not exhaust, then its gotta be in the transmission when it's under torque.

How old is the clutch? How many miles on it and transmission?

I'd take a look at the clutch/transmission/torque converter.

Interesting problem. I hope it's not too serious.

listened to vid - ujoints sound likely as many mentioned.

This message has been edited. Last edited by: Oz_Shadow,

It definitely sounds like something that rotates is contacting some thin sheet metal...or vice versa.

Two places where those two elements are in play that immediately come to mind are the fan & shroud or brake drum rubbing a backing plate. You said braking doesn't seem to affect the sound so I'd lean toward the fan. Have you tried tapping the brake pedal while keeping the engine under sufficient load to produce the sound?

Re the sucking sound, yes, I can hear it. If a bad motor mount is involved as suggested above, than you could have ripped a vacuum line or fitting.

For your sake, I hope you get this issue resolved quicker than the electrical problem from a few years ago. And I think it's cool that you're still driving that car.

Check the u-joints.

I can't watch the video now because of my bad network.

If the u-joints have zerks in them, squeeze in some grease. Either way, install new u-joints. Cheap and easy enough to do.

I just jacked up the rear end so both drive wheels were off the ground. There is no play in the pinion/unlit/driveline relationship. The whole assembly, if you will, has maybe 2 degrees rotational play, which I assume is normal

quote:

Originally posted by ScorpionBoy:
i would take a flashlight and look for any bare metal for starters. I agree it sounds like something is spinning around and rubbing. pramblett might be onto something. are your motor mounts warn out?

Didn’t notice anything but I also didn’t really look for that. I’ll have to check. It’s a bit hard to see as the mufflers do a great job of hiding the rear u bolt.

quote:

Originally posted by Shaql:
I hear a couple of tics when you stopped and rev'd the engine.

Check for an exhaust leak.

Now that you mention that I hear the ticks too. That’s indicative of an exhaust leak? Where would the most likely place be? The car has headers on it, not an exhaust manifold. Also has the cross pipe behind the headers.

quote:

Originally posted by Sig2340:
Sounds like a loose exhaust heat shield rubbing on the driveshaft.

Don’t remember seeing any shielding but I’ll confirm next time I lift it up.

quote:

Originally posted by Perception:
How are your motor mounts?

Also, check your driveshaft and exhaust for any play or shiny spots that look like they might have started rubbing on something they shouldn't be rubbing on.

quote:

Originally posted by MooneyP226:
Sounds almost exactly like my '85 K5 Blazer did when the exhaust flanges let go before the cats.

I'd look for hanging pipes and/ or soot/ scorch marks along them.

Did you use non-metallic flange gaskets? Welded exhaust? Headers loose at head?

Couldn’t answer you as to the motor mounts. I imagine they are original, so likely showing their age?

I’ll have to inspect the exhaust all the way back.

quote:

Originally posted by Stlhead:
It could also be a weak bendix spring on the starter that is allowing the spur gear to contact the flywheel. when it warps under load.

Is there a way to confirm this is or isn’t the problem besides installing a new starter?

quote:

Originally posted by Oz_Shadow:
Pump in the transmission.

Can you elaborate?

quote:

Originally posted by FRANKT:
It definitely sounds like something that rotates is contacting some thin sheet metal...or vice versa.

Two places where those two elements are in play that immediately come to mind are the fan & shroud or brake drum rubbing a backing plate. You said braking doesn't seem to affect the sound so I'd lean toward the fan. Have you tried tapping the brake pedal while keeping the engine under sufficient load to produce the sound?

Re the sucking sound, yes, I can hear it. If a bad motor mount is involved as suggested above, than you could have ripped a vacuum line or fitting.

For your sake, I hope you get this issue resolved quicker than the electrical problem from a few years ago. And I think it's cool that you're still driving that car.

I will check the fan and see if there is anything real close that looks like it might be able to move enough under torque.

To look for vac leaks can I spray carb cleaner or wd40 around the engine bay and listen for changes in rpm?

What was the electrical problem a few years back? This car has been causing me issues for 15 years now. Lol. They tend to blend together.

quote:

Originally posted by Shifferbrains:
Check the u-joints.

That was my immediate answer.

Mid shaft hanger bearings will also make that same noise when they go bad, but you shouldn't have one I wouldn't think.

quote:

Originally posted by Stlhead:
It could also be a weak bendix spring on the starter that is allowing the spur gear to contact the flywheel. when it warps under load.

Yep. It sounds "flywheel-ish". (Flex Plate) Pull the inspection cover off the bottom of the bell-housing and see if there is any metal dusting.

You can have problem with torque converter being pushed forward against the flex plate from overpressure due to filter, passages and other things.

That whistling sound at the end sounds like the torque converter.

But it is hard to diagnose with a video.