Low whining sound from undercarriage

[ZR11974]

Good morning to all. I hope this email finds everyone well.
I am a new ZR-1 owner and am hoping I can draw on the vast knowledge, here.
The car is a white 1990. It only has 30K on it and is in excellent condition. I love the car. Lifelong goal achieved by getting the legendary LT5 underfoot.
However, I am experiencing a low whining/whirring type sound from under the car. It does not seem to be changing the cars performance. It's just a concerning sound, and it's loud.
It does not appear to be exhaust.
It is not throwing any warnings, and none of the battery, oil pressure/temp, or normal temp gauges are effected by it. Neither is the idle. It sounds like it might be a belt. But, it starts and ends while moving or sitting still, and it never continues once I accelerate. And, as best as I can tell it appears to be coming from the front/center of the car, not the rear.
Steering also doesn't seem to be related.
I keep trying to isolate some consistency with it, but no luck so far.
And, as I've said, it is loud. Almost like a smaller engine is revving, but not the LT5.
Since it comes and goes with clutch release and depression...sometimes...clutch is my gut feeling.
Any troubleshooting suggestions? I have considered buying a code reader, or using a paperclip trick I read about to see what is stored on the ECM.
I absolutely adore the car, and this weird *** sound is the only thing I'm concerned about.
Thanks for taking the time to read all this, and I hope the day treats you all well.

Respectfully,
Geoff

[Paul Workman]

The 90s have straight cut gears in the ZF which produces some gear whine, especially in 1st and 2nd, I find (in my 90 as well). AND, it comes when the clutch is out and goes away when the clutch pedal is engaged. But, if you noise is the opposite, then throw out bearing comes to mind - except seems unlikely with so few miles.

There are many members in your area that might be able to drop by your location and assess the sound with a learned ear. Aside from that, have you changed the transmission fluid yet? Changing the trans and differential fluid - may or may not improve the sound (if coming from the trans), but then you can check that off the list and you'll know that isn't the issue.

Perhaps Mark Horner or one of several other local Texicans can give it a listen. And, given that gear whine is the nature of the beast in the 90 to mid 92s, if that is all it is, the fix is turning up the radio or installing headers w/o cats! (kidding ya!)

[Hib Halverson]

Originally Posted by Paul Workman

The 90s have straight cut gears in the ZF which produces some gear whine, especially in 1st and 2nd, I find (in my 90 as well).

(snip)


There are no "straight cut" gears in any version of the ZF S6-40.

Gears in the early 6-40s have a slightly smaller helix angle and that's why the early transmissions are a little more noisy and have a little higher input torque rating.

[Paul Workman]

Originally Posted by Hib Halverson

(snip)


There are no "straight cut" gears in any version of the ZF S6-40.

Gears in the early 6-40s have a slightly smaller helix angle and that's why the early transmissions are a little more noisy and have a little higher input torque rating.

A picayune distinction, to be sure, Hib.

[Hib Halverson]

Originally Posted by Paul Workman

A picayune distinction, to be sure, Hib.

Granted, you've got me beat on the vocabulary front. I had to look up the meaning of "picayune".

Nevertheless, Paul, if you knew a bit more about manual transmissions you'd not say that.

I'd like to suggest that when you're making statements about subjects on which you lack accurate information, maybe you should think twice about commenting.

[Paul Workman]

Originally Posted by Hib Halverson

Granted, you've got me beat on the vocabulary front. I had to look up the meaning of "picayune".

Nevertheless, Paul, if you knew a bit more about manual transmissions you'd not say that.

I'd like to suggest that when you're making statements about subjects on which you lack accurate information, maybe you should think twice about commenting.

Oh... THIS certainly went off the rails! It isn't going the way I intended! I meant no disrespect, Hib. OK, I'll admit in jest I was just "pokin' the bear" a little, but thought you'd "get that" - that I was really giving you a sort of a "left-handed" compliment.

(edit): Everyone...should think twice before saying stupid, derogatory, and unfounded chit on an open forum. Especially the two of us.

Sorry for the misunderstanding, Hib. (Shoulda taken my meds first.)

[Dynomite]

Originally Posted by Hib Halverson

(snip)

There are no "straight cut" gears in any version of the ZF S6-40.

Gears in the early 6-40s have a slightly smaller helix angle and that's why the early transmissions are a little more noisy and have a little higher input torque rating.

I find that information very interesting....thanks Hib

[Dynomite]

Originally Posted by ZR11974

Good morning to all. I hope this email finds everyone well.
I am a new ZR-1 owner and am hoping I can draw on the vast knowledge, here.
The car is a white 1990. It only has 30K on it and is in excellent condition. I love the car. Lifelong goal achieved by getting the legendary LT5 underfoot.
However, I am experiencing a low whining/whirring type sound from under the car. It does not seem to be changing the cars performance. It's just a concerning sound, and it's loud.
It does not appear to be exhaust.
It is not throwing any warnings, and none of the battery, oil pressure/temp, or normal temp gauges are effected by it. Neither is the idle. It sounds like it might be a belt. But, it starts and ends while moving or sitting still, and it never continues once I accelerate. And, as best as I can tell it appears to be coming from the front/center of the car, not the rear.
Steering also doesn't seem to be related.
I keep trying to isolate some consistency with it, but no luck so far.
And, as I've said, it is loud. Almost like a smaller engine is revving, but not the LT5.
Since it comes and goes with clutch release and depression...sometimes...clutch is my gut feeling.
Any troubleshooting suggestions? I have considered buying a code reader, or using a paperclip trick I read about to see what is stored on the ECM.
I absolutely adore the car, and this weird *** sound is the only thing I'm concerned about.
Thanks for taking the time to read all this, and I hope the day treats you all well.

Respectfully,
Geoff

Difficult to understand exactly when you hear this "smaller engine revving".

Seems most likely Serpentine Belt or tensioner but then you associate Clutch operation which is confusing

We have the AC, Water Pump, and Power Steering as well as Alternator rotated by Serpentine Belt Also.

[ZR11974]

We can all rest assured I am confused, as well. Haha.
I have not changed the fluids, yet, but considered that. And, I am almost certain it's not the well-documented ZF gear whine. I think I hear that, and I actually love it. Haha.
I'll check out the Serpentine belt, visually and see if anything looks amiss.
And, I'll see about reaching out to some of the Texan locals!
Thank you very much for the ideas, and suggestions.

Geoff

[Mystic ZR-1]

Pilot bushing?