So, I had my clutch, torque tube and rear diff recently replaced. I needed the clutch and the torque should be rebuilt while it's apart, but since it would be apart anyway...why not swap the gear (and the C6 Z06 internals), right? Anyway, I got it back from the shop and everything was great. The clutch was like butter, no noise from the rear - the drive-line felt fresh/new. I followed the break in procedure for the diff and literally on my way back to the shop for the diff flush after 500 miles I heard a faint whine on light load from 3rd gear on up. The tech at the shop said the fluid looked typical for a post diff service flush. The shop is well know and reputable locally. They do a bunch of C5/C6 work and support lots of local guys that autocross their cars. However, they subbed out the diff work to a guy the owner knows/trusts/uses.

Anyway - I don't think there's much I can do immediately besides keep an ear on it to see if it get louder, but I figured I'd put it out there for any thoughts/suggestions. Thanks.

 

How many miles? The whine could also be your wheel bearing(s) Might just be a coincidence on the diff replacement. If the shop checked it out and said it was fine look into the bearings.

 

From 3rd gear on up...so is it dependent on vehicle speed or engine speed? Engine speed might be trans related...vehicle speed might be the diff or wheel bearings, etc. A bit more description of the sound and conditions would be helpful.

I had 4.10's swapped into my diff with C6Z guts by DTS in Warren. It's silent except for faint whine at part throttle between 75 and 85 mph. I've yet to take it back to them because it's really faint and hasn't gotten worse. I've heard the gears just make a bit more noise, and that might be what's going on.

 

The noise is related to vehicle speed not engine speed. No noise on acceleration or deceleration, just a light load - say holding a constant speed. Yes, 3rd gear through 5th for sure. It just started the other day and I haven't been on the freeway yet. I read your build post - did the same C6Z06 guts with a 3.90 Motive gear. It's faint, that's for sure. Wheel bearings would be a relief.

 

65,000 miles. I'll look into the wheel bearings.

 

Yep, sounds just like what mine does. It's entirely possible that's just what gears do.

I think I'm going to take it to DTS next week and have them listen to it and let me know what they think and report back. Since you're local, we can also meet up and compare noises if you'd like. I live right off Woodward in Ferndale, so if you're down at all for the dream cruise next week, let me know.

 

We should compare. Curious what DTS says about yours. I heard the same - a little noise is not uncommon. It's odd it was whisper quite for the first 500 miles??? I'm going to miss the cruise (family vacation in the U.P.). There's a car show/event at M1 Wednesday evening I plan on attending. Looking forward the checking out the track.

 

Since mine only makes noise above ~75 mph, it didn't show up during break-in (supposed to stay under 55mph during break-in). It's silent otherwise that I can tell, and has been since break-in.

One thought is oil. DTS highly recommended running NON Synthetic gear oil. They said that when synthetic gets hot, it's a bit thinner than non-synthetic and non-synthetic helps keep things quieter and the diff healthier (as long as you run friction modifier for the clutches). I've heard of this for engines, so I've heeded their suggestion for both break-in and after 500 miles. It seems to have kept it quiet (at least outside of 75-85 mph).

Anyway, I'll let you know what they say when I bring it by. I didn't know there was an event at M1 Concourse...I haven't been there yet and I've been curious to check it out. Have fun! Oh, and I'd much rather be in the U.P this weekend too! Dream cruise has just become a traffic jam to me.

 

Any new developments here? What did DTS say about it? Did the noise get better/worse??

 

Still haven't had a chance to get it to them (which is kind of ridiculous since they're 4 miles from my office), but work has been hectic, blah, blah excuse, excuse.

Anyway, I've put a few thousand miles on the diff now, which includes getting it dyno tuned (443 WHP!) and the noise hasn't gotten better or worse. Still nothing below 75 mph, and nothing above 85 mph. And it's only faint on part throttle. Might just be how it is?

 

wouldnt worry about it

 

Ok, finally got the car to DTS. I described the condition to the tech (whine only part throttle between 75-85 mph). He took it for a spin and came back and confirmed. He said it's just the nature of aftermarket gears. He described the condition on mine as "float" where the pinion teeth are barely making contact with the ring gear teeth...he said it's quite common for aftermarket gears to make noise under this condition, and it's nothing to worry about as long as it's within a 5-10mph range. He confirmed mine above 75 and thought it was just fine (though did suggest not to drive much above 80mph due to something called "speeding").

He said a sign of a bad setup or gears would have whine over a wider range of speed OR noise on accel or decel.

BTW @Time for a C-5, the guys at DTS in Warren are super friendly and helpful. If you want a second opinion on your gears, I bet they'd be willing to check it out for you.

 

Thanks. I need to get over to see them. It's quite on acceleration and deceleration but is present over a wide range of speeds.

Do you know if adjustments can be made with the pumpkin in the car or does it need to be pulled?

 

I highly doubt anything can be done to the diff without pulling it. BUT, I think it's probably worth having someone check it out to know for sure.

 

Well, I got over to DTS this am and Don took it for a ride. He didn't like what he heard. His best guess is that it wasn't heat cycled properly. The shop that did the work didn't mention the procedure to me and it wasn't done. Grrr! They said $600 in labor to r and r the gear. I still have my 3.42 ring and pinion and I know that would be whisper quiet. I'm thinking about just putting that back in.

I did enjoy the 3.90. I also though I should have gone to the 4.10. Where's your RPMs on the freeway at say 70 mph?

 

Oh, gah! Break-in is critical. When I picked up my diff, DTS was very detailed with break-in procedure. There's also some good guides out there to follow, like this:

http://www.zip-corvette.com/download...structions.pdf

$600 to drop the diff and fix isn't bad. I brought them my diff off the car, so I can't speak to the overall quality of their work, but my diff has been solid.

I LOVE my 4.10's. Best mod I've done to the car. The RPM change really isn't that bad...it's a bit under 2k RPM at 70. I'll have to pay attention next time I drive it to get the actual number.

BTW, if you want a ride in my car before you decide, let me know. IIRC, our mods are very similar. Traction is horrible in this cold weather so acceleration runs are futile, but you can hear the diff and experience the cruising RPMs on the highway. I'm in Ferndale and would be happy to meet up.

 

This is the one mod I gave serious consideration to when I was doing my Grand Sport project that I didn't do. Gear whine was my hesitation. Had gears put gears in my Cutlass many years ago and they whine...not that you can really hear them over the flowmasters

Nonetheless, the Vette is much quieter than my Cutlass and whining gears would drive me insane.

But, I continue to think about it...agree that from a bang for the buck perspective, a move to 4.10's would be hard to beat.

Would love to hook up with you guys sometime!

 

Yes, for sure. I've meant to get to the Lingenfelter cars and coffee but it never happened over the summer. I believe I've seen pics of your Cutlass there. Your GS stripes would be easy to spot. The cars and coffee at the M-1 concourse has developed into a nice event too. Definitely worth checking out next summer.

 

When I had the clutch replaced I had a set of RPM 4.10s installed. RPM and the shop (Futral Motorsports) that did the work were even more specific than the zip-corvette pdf.-- they didn't seem to prefer a type of oil-- synthetic vs non-synthetic, but they were emphatic that I keep the speed below 50mph for the first 500 miles and that I not keep a steady speed for longer than ~7-10 minutes.

I was told to vary the speed according to that time limit, and stop every 20-30 miles to let the oil "completely cool down". It was as bad a sin to keep a constant speed as it was to go over 50mph in the first 500 miles.

Ideally, I suppose I should have had the car towed home; I drove it the ~200 miles. It took me almost 15 hours; when I picked up the car, I didn't know I had to let the oil cool down, I only knew about the <50 mph and 'vary the speed'. I thought I could do that all the way home, so my ride to the shop drove home. After I paid for the work, they detailed the break-in procedure (including 'let the oil cool completely') and I was "stuck". I used the DIC to show me the engine oil temperature, and when it dropped to ~90*, I'd start up again and drive ~30 miles and stop, repeat, etc. (I can't remember the source--one of the two said later that I should have "let the oil cool overnight" so obviously, these break-in runs are supposed to happen with 'home' as a starting point.)

I followed their directions "within limits"--the limit being, I wouldn't wait for the diff oil to get cooler than 90*. (Ambient temps were 75*+ all day.) The good news is, there's no whine--at least, there isn't one that I can hear above the exhaust and engine noise.

The engine RPMs are just barely under 2100 at 70mph, and ~2350 at 79mph.

I dropped the differential oil at 500 miles and replaced it with Amsoil Severe Gear 75w-90 and the LS additive; then I replaced that all again at 1,000 miles just to be sure. I've since replaced it a 3rd time at 15,000 miles' use, and the oil looks pretty damn clean. The first change looked like glitter.

 

I made it to Corvette day (or one of them?) at Lingenfelter and was one of only a few C5's. I need to hit up M-1 next summer. The usual cars and coffee at Pasteiner's in Royal Oak is always crazy too.

Would be neat to meet up and actually ride around in cars. Though warning: once you experience 4.10's, it'll be hard to go back.