Screech sound on heavy acceleration

[tx73vette]

I had a similar noise like the one you mention ... It turned out to be a brokren motor mount so every time I stomped on the gas the fan touched the fan shroud. look at your fan and see if this might be the problemm...
Hope that this helps.

Daniel

 

[Blade]

Found your problem

Several C3s have been reportly getting upset, even screeching and smoking mad, about the new C6.

 

[David Evans]

In the old days a highpitched squeal from the rear meant a wheel bearing. Maybe you have a half shaft bearing going. Drive it and check for differences in heat from the left to the right. sounds torque related (load related) if it only does it under hard acceleration. LOL

 

[curtis]

sounds like when my rear wheel bearings were toast.

 

[Stallion]

But if it were my rear wheel bearings, then why would it only happen under heavy acceleration? And it's not constant.

You are right though, maybe I should just change them out. What kind of job is it to do that? Anybody have a little run through for me?

 

[JohnZ]

Check out the diff support bracket bushings first - it's unlikely based on your symptoms that the wheel bearings are involved.

Wheel bearings are a big job, requiring special tools, a press, and precision measuring equipment, and are best left to shops/pros who do them every day.

 

[Stallion]

John (or anybody), how exactly will I know if it's the diff support bracket bushings? I mean, I won't see the car make the sound because i'll be under her. What should I be looking for?

Thanks.

 

[Stallion]

Pictures!

Okay, here are some pictures when I was under her. The first picture is of "something" I found. It was on the "tunnel" of the driveshaft and where it goes through. It seems like a long, clean line out of the ordinary. It's not very thick at all. But it looks like there might have been some rubbing. But I don't understand, the driveshaft would have to go up pretty far to do that. Maybe under heavy acceleration it does (if that's the problem).

The next picture is of the bushing. What do you think? Bad? Good? I can't compare it to anything. Ideas?

Please have a look and give me some ideas/suggestions/solutions.

 

[Eddie 70]

Diff bushing looks to be okay.

 

[Stallion]

What do you think about the "rub" line?

 

[vettepilot]

Are you certain that's a "rub line", in the photo it looks more like a crayon marker was used to make that line and may have been there since the assembly line. Plus, I couldn't see evidence of any rubbing on the rotating component/driveshaft. Any time a rotating component touches a stationary surface, it will leave a polished mark on that component.

Have you looked at the top inside of your wheel wells in the rear? Or on the frame forward of the rear hubs. If you have other issues in the rear end, under hard acceleration, the rear wheels may toe-in more than normal, and could be making frame contact on the inner surface of the tires. Look for evidence of rubbing against the frame.
Does the car seem to squat more than it used to during acceleration? If so, look for evidence of rubbing on the top inboard side of the wheel housing, the tire could be making contact because of excessive neg. camber.
Any chance that you have just installed larger tires lately? You didn't mention it, or I didn't see that you mentioned it, if so, double check the clearances around the tires. Do you have the OEM style wheels and correct OEM offset?

Throwing all this out as food for thought and areas to check if you found nothing else so far.
Oh, and what JohnZ said about changing wheel bearings is all true. I have seen the thick steel plate on the special tool puller bend under the tremendous force required to break free heavily rusted and frozen bearings. Not a fun job at all.

vettepilot

 

[Stallion]

No, that rub line is definitely the lack of dirt. In fact, that little line perpendicular to the long rub line, was actually my finger rubbing out the dirt.

Tires/wheels are all stock (well, tires have stock dimensions and have never been a problem before). She seems to be sitting normally. Maybe if the shocks went on me, then it would squat lower? But it seems to be sitting fine.

Ughhhh...what do I do now?

 

[curtis]

watching yur posts and it still seems to me you have something rubbing when yu step onit or the rear bearings are worn enough they squeel under the torquecheck for too high clearances in wheel bearings. also is it possible yur strut rod bushings are worn and the wheel shifts over to rub on the end of the rear spring or the park brake line mount on the side of the torque arm? look for rub marks on the inside of your rear wheels.

 

[elseyj]

Looks like your "rub line" was caused the last time the driveshaft was removed/installed.

 

[Stallion]

Tires/wheels look fine. No rub, nothing. Now what? I was under there, there are no clean rub spots. I just don't know what to do now.

 

[wishuwerehere82]

Did you fix your tranny leak yet?

 

[Stallion]

No, that seems to be coming out where the tach goes into the tranny. I have to check that out.

 

[Bob Chadwick]

Tach is electronic. I think that is where the speedo goes into the tranny.

 

[Stallion]

Yes, typo on my part. I meant the speedo.

And a little update. I'm thinking it might be the suspension. I was just driving normally and there was a little drop in the road. When I went over that, I heard that same sound as I do when I accelerate hard in 1st and 2nd gear. So maybe it's the suspension? But what on the suspenion causing this?

 

[brusso]

Yes, typo on my part. I meant the speedo.

And a little update. I'm thinking it might be the suspension. I was just driving normally and there was a little drop in the road. When I went over that, I heard that same sound as I do when I accelerate hard in 1st and 2nd gear. So maybe it's the suspension? But what on the suspenion causing this?

Leaf spring shims or spring link bolt bushings.