tlrskunk

SO i've had my 01 Z06 for about 3700 miles now. (64,473 miles total)
I bought it in April. First Corvette.

Within 1500 miles I devoloped a rod knock. So motor came out.
Fresh rebuilt .010" over pistons, MS3 cam and springs. Long tubes with catless X-pipe and tune. new LS7 clutch new slave/Throw out bearing.

Since i had gotten it I've had a drive train whine. Did some research and found most people saying it's relatively normal for a z06 to have some whine so i ignored it.
Fast forward to the first of June i made a trip to Oklahoma in it.
Did a few high way pulls and noise went from a whine to a growl.
The growl is most noticeable when on light throttle maintaining speed.
So say 3rd gear 1500 RPM cruising at 35 ish and add light throttle it's terribly loud. happens in 4th, 5th, and 6th at the same RPM range and higher. if you are wide open you can't hear it over the exhaust.

I thought it was torque tube bearings so i rebuilt my torque tube new bearings and rubber spacers. The rear bearings were a little notchy but not as bad as i expected so i thought they would be my source of noise. Put it all back together and drove it home. exact same noise.

So now i'm not sure. it's for sure a bearing noise. But is it trans or Diff?
my Trans shifts nicely and doesn't grind or pop out of gear.

Help!

MY03C5Z

How many miles are on the car?

tlrskunk

I got the car with 60,311
it now has 64,473 according to my logs.

bikeriderga

Sounds like somebody has rode it hard and put it up wet. You should not be having all of these issues on a mid mileage Z06!

Are you drag racing by any chance? Since you stated you installed a new clutch assembly, I am going to rule that out (but keep in mind still could be related), rear wheel bearings, rear brakes, or it could be in the differential.

Without knowing the exact sound, kind of a guessing game.

If you can get the rear end up in the air, easy to check wheel bearings and brakes. If you can get it up on a lift and go through the drive train while running, should be able to track it down (if not wheel bearings or brakes sticking [caliper or ABS]).

Are you throwing any codes? That's the first place to start.

Might want to at least put an OBD2 device in and go through a full diagnostics sweep as well. No need to be replacing parts if the PCM, BCM, or CCM can tell you where the issue is coming from!

MY03C5Z

Sounds like this car may have had a hard life. How many owners? As mentioned above get the car up in the air, turn the wheels and see if you hear any obvious bearing sounds would be a good place to start.

tlrskunk

I'm not drag racing it. Mainly a street car.

I think it had one previous owner I bought it used from a dealer and don't remember.

bikeriderga

Are you throwing any codes?

tlrskunk

No codes

bikeriderga

OK, I would start looking at wheel bearings and rear brakes next.

Another one I have seen, is loose mufflers. If they are loose, they could be dragging or rubbing against metal and make a grinding type sound,

tlrskunk

Wheel bearings are tight. Noise doesn't change when you swerve left to right.
and brakes would make noise all the time at speed. This noise goes away when in neutral or clutch pushed in/disengaged.

Mufflers are definitely tight as i have had the exhaust off and on. I have no exhaust leaks.

fuggles

If it is going away in neutral, as you suspected, I would also suspect tranny or diff. Maybe change the fluids to high quality synthetic and see what happens.

tlrskunk

I think I'm beyond a fluid change fix
and it's definitely going away in Neutral.

Pulling it back apart tonight.
Swapping with a known good diff. re-assembling and will test drive.,
If noise is gone will replace/rebuild diff.
If noise is still there i will be replacing trans.

Luckily a local friend races them and has a spare 3:42 diff I can borrow.

Supercharged111

Come on guys, you are really shooting from the hip here. RPM specific rules out wheel bearings and diffs. Since it wasn't the torque tube the only logical thing remaining is the trans. Drain the fluid and see how much metal comes out. I'm guessing if you rev it with the clutch in it doesn't do it?

MVR 155

^^^^^^This^^^^^^

If the noise ceases in neutral or when the clutch is depressed that leads me to certainly believe it's a trans related issue. I don't think I would waste your time on swapping the diff out.

bikeriderga

Once you added noise goes away in neutral or when clutch is engaged then yes, sounds like tranny or diff. Most likely in the transmission.

Other suggestions were to eliminate potential easy to fix issues. Hard to diagnose problems concerning a sound that I cannot hear!

tlrskunk

Thank you.
I probably should have included this to begin with about teh clutch and I really thought i had.

Yea i said **** on it and ordered a trans and diff. I figure if I've rebuilt the motor and the torque tube I might as well start all fresh drive train wise with the car.

oharal

I had something similar on mine. Terrible howling noise from the diff. When I had the trans (separate issue) and diff rebuilt, the guy found the outdrive bearings were so shot the carrier was dancing around inside and the ring/pinion gap was changing. It munched the whole diff and nothing was salvageable so I bought a new used diff.

tlrskunk

My new plan is just replace both and know it's all good. i'll pull diff cover when i get it all out and inspect since I have to drain both before shipping the cores back.

oharal

When you get the transaxle down, grab the little bit of the outdrive stub that protrudes from the side of the diff and try to wiggle it. Mine would move almost a millimeter in any direction. They should be pretty well rock-solid.

tlrskunk

i plan to pull the cover and take a look out of curiosity