Where's this noise coming from?

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genepewl

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Warner Robins, GA
My 72 Duster with 318/904 has been making a high pitch rattle lately. It almost sounds like the sipping of the last bit of soda from a cup with a straw, but more like a high pitched rattle. It occurs when accelerating and above normal engine load (hills). Regular cruising is quiet but I feel a slight and inconsistent surge that's not unlike warped brakes. There's also clunk and jerk when changing gears from P or N.

I'm no pro, but my gut is telling me it's the torque converter. Ideas?
 
Only on hills and acceleration?

Check your timing. You may be detonating under load, not a good thing. Mine did this before I figured out I was getting close to 50* advance when the vacuum advance kicked in. The surging could also be a lean condition, which would also go with a detonation issue under load. The factory calls for very little initial timing at idle, and the mechanical and vacuum advance are set accordingly. If you're initial is 10-12* advanced or more, its easy to end up with too much timing all in.

But 73's right, it could be any number of things. However, if it was the torque converter my bet would be that it would be happening all the time, not just under load. The clunk is probably just a fluid level issue, or maybe a linkage adjustment. Check the transmission fluid for level and color. Seems like no one ever changes the transmission fluid because of the lack of a drain, its amazing what fresh fluid and a new filter will do for an auto.
 
Check your universal joints. They can have a bit of a vibration as well as a high pitch squeal. Kinda like a high pitch chirp chirp chirp with some vibration?

Make sure there is no load on the driveshaft ( chock the wheels and then slip it out of park and then back into park, that should release enough tension so you can check them) check front and rear up and down side to side and try and rotate to see if you find some slop.
 
To me it sounds like you guys are correct, I thinks it's Both Detonation AND U joints.
At least without more to go on.
 
We did just move and dropped 2000 ft, so the carb does need a tweak. Would the altitude change require a timing adjustment too? I had it set pretty good a couple months ago. My tools are in storage, though. :tard:

Revving in neutral or park doesn't produce the noise. I only notice it while in motion. That's why I suspect it's happening behind the motor. I'll have to see if the noise occurs in gear with brakes engaged. If it does then I can capture the sound pretty easily. Any suggests for in-motion sound capture?
 
Get somebody with some tools. Put rear differential on jack stands. Make sure car is on there good. Chock front wheels. Start it up an look at drive shaft for wobble. Have some one change gears. Make sure they hit the brakes and stop the wheels before shifting from D to R. Don't get hurt.
 
genepewl said:
We did just move and dropped 2000 ft, so the carb does need a tweak. Would the altitude change require a timing adjustment too? I had it set pretty good a couple months ago. My tools are in storage, though. :tard:

Revving in neutral or park doesn't produce the noise. I only notice it while in motion. That's why I suspect it's happening behind the motor. I'll have to see if the noise occurs in gear with brakes engaged. If it does then I can capture the sound pretty easily. Any suggests for in-motion sound capture?
Click to expand...

The altitude drop could need a carb and timing adjustment, absolutely. 2000 feet isn't a lot of change, but if the adjustment was borderline to begin with that's more than enough to need some tweaking.
 
[ame="http://www.youtube.com/watch?v=TzAlSF2djZQ"]http://www.youtube.com/watch?v=TzAlSF2djZQ[/ame] Sound in question starts around 0:16

[ame="http://www.youtube.com/watch?v=RQSjeyzVzgA"]http://www.youtube.com/watch?v=RQSjeyzVzgA[/ame]
 
I forgot to add that it was in drive with the parking brake engaged in both videos. It does make the noise in neutral, but it was so faint that I couldn't hear it without the hood up.

The guy that I dealt with at the consignment lot I bought it from said it had a stuck lifter. That ticking noise stopped after a Sea Foam treatment.

I haven't checked the u-joints yet. The ground gets really friggin' hot here, so I'll have to do that in the morning. We move into our apartment tomorrow so I'll have access to my garage and tools soon enough.
 
genepewl said:
I haven't checked the u-joints yet. The ground gets really friggin' hot here, so I'll have to do that in the morning. We move into our apartment tomorrow so I'll have access to my garage and tools soon enough.
Click to expand...

With it sitting, no movement it's not U joints.. It wouldn't hurt to check them though if the car is new to you.


As far a hot ground a good piece of cardboard to lay on will help.
 
Can you post a pic of the engine, both sides, around the exhaust manifolds. Be sure to resize them so the thread doesn't get all warped out of shape.
 
I've noticed that the rate and pitch of the noise doesn't change through the throttle sweep. Some kind of threshold is met and a consistent noise occurs.
 
genepewl said:
I just want to check them for the clunk and jerk from shifting.
Click to expand...

As I said it wouldn't hurt. The clunk you're hearing could be the rear end, they are notorious for that when getting worn.

The more I listen to it, it sounds like metal to metal. Pretty hard to tell through a video.
 
genepewl said:
I've noticed that the rate and pitch of the noise doesn't change through the throttle sweep. Some kind of threshold is met and a consistent noise occurs.
Click to expand...
does it sound like its coming from inside the engine?

it almost sounds like a valve is floating or lifter rattle. ive heard a similar sound from a bad wristpin but that was through the entire rpms.
what about the heat riser in the exhaust manifold?
 
Sounds like spark knock to me. Check/adjust the timing. If you have a dial back timing light handy make sure it doesn't go over 34 degrees total timing with the vacuum advance unplugged and engine revved up to 3000-3500 in neutral. You could also try higher octane fuel if you don't have any tools available. Since you moved to a lower altitude it may also be running a little lean. As 72blu said 2000 ft isn't a big change but if it were borderline to begin with it may be 2-3 jet sizes lean now.
 
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