JT2000WS6

Hello, all. I’m trying to pinpoint the source of a noise and need some help.

When I have the car in gear driving down the road and take my foot off the gas to coast there’s a sound that I can best describe as the that of paper being crumpled or sand being poured on a sheet of tin. The sound is there at any speed really but is easier to hear at moderate to high speeds. The noise is only there when in gear and coasting/foot off the gas. As soon as I tap/apply the gas pedal, even very lightly, the noise goes away. If I coast with the car in neutral there is also no noise to be heard.

Relevant specs (I think):
-M6 w/ LS7 clutch (rebuilt 35k – 50k miles ago. Not sure exactly but it’s not the original clutch)
-10 bolt posi w/ 4.11 gears. I changed the diff fluid about 2k miles ago and everything looked clean at that time.
-Long tube headers going into an ORY, no cats.

Anyone have any idea what this noise may be or how I can diagnose/track it down?

Thanks again!

wssix99

iTrader: (5)

Moving to Manual Transmission from General Maint. to get closer to some ideas. Given that the problem goes away in neutral, I'd expect this to be in the transmission or drive train.

tug686spd

iTrader: (11)

Most likely the noise is coming from the rear end. Especially since the gears have been changed.

JT2000WS6

Is that a common sound for a rear to make? I was hoping for something cheaper, like possibly u-joints

Any other possibilities other than the diff?

conan

iTrader: (5)

Did you check the U joints ? Usually failing joints will make noise when they are un-loaded and can "float" then quiet down when the load hits them again.

tug686spd

iTrader: (11)

Its a fairly common problem if its what it turns out to be. Its possible to be u-joint but they usual just squeak or squeal under load. Your noise isnt present when there is no load at all on it and onky there when a negative load while decelerating. Ive been trying to think of the terminology for the gears all day but drawling a blank. Depending on if its making noise with acceleration or deceleration tells you whats out of spec in the rear. Someone with more experience will be able to answer this for you.

On a side note most people who drive these cars the way they were meant to have this noise and it goes un noticed do to the exhaust and stereo until it gets really bad. When you changed fluid what did you use and did you put any additives in whith it?

tug686spd

iTrader: (11)

Couldnt take it anymore and had to google what I was trying to say heres a good read with all the terminology and what conditions cause each.
https://www.google.com/url?sa=t&sour...TylJmIgu68kDNw

JT2000WS6

I changed the diff fluid because I was hearing noises (separate from the noise I'm posting about) when making turns after it warmed up. When I changed the fluid there were no shavings present, the gears looked clean, and I added the proper additive. The noise I changed it for went away immediately.

The noise I started this post for has been present for the last 2+ years I've owned the car. It's always been there and I have not noticed it getting any worse over time. I need to address it and figure out where it's coming from though.

R6cowboy

iTrader: (3)

I'm thinking the noise you're describing is coming from the diff, especially since it has been there for the past 2+ years since you've owned the car and is not getting worse. My guess is the gears were not shimmed perfectly when the 4.10's were installed and that's what is causing the noise. I won't say this is a very rare instance, I've heard of this type of thing many many times, and it could make the noise for a very long time without causing failure or any real damage. The bright side is, if that's the actual corporate, it shouldn't be a really expensive fix. It shouldn't take an experienced mechanic more than about 3 hours to re-shim a 10-bolt.
But if I were you, I'd start by spending the $20-30 replacing both U-joints just for peace-of-mind.

JT2000WS6

Just checked the u-joints. They're tight. There is some play/slack from the engine to the rear but I think that would be normal.