Got a Funky, Barely Audible Drivetrain Noise

[rand49er]

After I had my UUC flywheel installed a couple of week ago, I've been driving around really listening hard to any abnormal sounds in the drivetrain, ESPECIALLY when I heard a horrible grinding noise while in 6th gear at 35 MPH with virtually no throttle being applied. Very nasty sound that I've never heard before.

Now, when I drive, I'm hearing a very subtle sound coming from somewhere in the drivetrain while the vehicle is moving whether the clutch is in or out, doesn't matter. I first suspected my new Hendrix Engineering axles and PM'd a few guys about it, and they all said they had no such noise, and their axles were performing just fine, so I've ruled out the axles. Mind you, I've crawled under the car several times, grabbed the driveshaft and exhaust and you name it and wiggled it all trying to duplicate the sound, all to no avail ... everything is bolted down nice and secure with no abnormal movement.

So, then I'm thinking it might be the diff itself. To complicate matters, I'm waiting to get my pinion seal replaced since it's leaking, and I was worried that it might be the source, but that just doesn't seem right. With the Specter bushings and the KARS kit, it whines like crazy but that sound and the one I'm talking about don't seem to coexist; they seem independent of each other for the most part.

A description of the sound is difficult. It's almost like a flag snapping in a stiff breeze only very muffled, or it's like a shaft or tube spinning in an opening that's slightly bigger in diameter, but again muffled. Frankly, I'm starting to worry about my tranny. One PM I got back during all this mentioned that Black Sunshine (Gene) had a tranny problem they thought was related to low speed, high gear operation, something I'm guilty as heck of. Maybe he'll chime in here.

Anybody else have any ideas? Thanks!

[smashn808]

Does it get louder with the AC on? When i had the UUC flyweel on my old M3 it made a slight rattle. Throwout bearing?

[CadiBlk]

You supercharge, tighten down the suspension like a lead pipe lock and make changes to the drivetrain and then think it's odd when a barely audible sound comes up. That's a tough one.

[CTSV_510]

Originally Posted by rand49er

Frankly, I'm starting to worry about my tranny. One PM I got back during all this mentioned that Black Sunshine (Gene) had a tranny problem they thought was related to low speed, high gear operation, something I'm guilty as heck of. Maybe he'll chime in here.

Anybody else have any ideas? Thanks!

I told ya, I don't see 6th gear until at least 40 mph, usually not til about 44.

Whether or not that has any bearing of what you're hearing, I have no idea.

[perfect]

Your V1 is mad at you for cheating on it with ORD's V2....

lol, my car is like a symphony of funky noises, snaps, crackles, and pops

[rand49er]

Originally Posted by smashn808

Does it get louder with the AC on? When i had the UUC flyweel on my old M3 it made a slight rattle. Throwout bearing?

Haven't turned the AC off, so don't know. Throwout bearing was just changed; besides, clutching has no effect on the sound.

Originally Posted by CadiBlk

You supercharge, tighten down the suspension like a lead pipe lock and make changes to the drivetrain and then think it's odd when a barely audible sound comes up. That's a tough one.

You have a point. But, I'd stack my car up against 99% of the CTS-Vs out there as far as being babied. My car rarely sees anything over 2k RPM, goes over RR tracks at < 7 MPH, and has had an occupied baby seat, now an occupied booster seat in it 99% of its life. Yeah, I admit it: Modding, in my case, is a hobby and is primarily for bragging purposes.

Originally Posted by CTSV_510

I told ya, I don't see 6th gear until at least 40 mph, usually not til about 44.

Whether or not that has any bearing of what you're hearing, I have no idea.

I'm hearing from a couple of guys, now, that my 6th gear may be worn out. Whether or not that has anything to do with the way I drive is unclear. Nevertheless, I called Luke to get pricing on a new one. Plus, I'm hearing that occasionally when someone has an issue with their tranny (unrelated to 6th gear), 6th gear gets replaced because it is sometimes found to show abnormal wear.

I could surmise at this point, that the stock FW may have dampened this sound before, but the UUC FW is allowing it to be transmitted as audible energy and into and above the threshold of my hearing. It's just a theory, mind you.

[Slithering_Joe]

Not sure about grinding but the last few times I was in a car with a lightweight flywheel it made quite of bit of rattling noise. The last car I was in was a BMW with a ultra-light flywheel and I swore I thought the noise was from the throwout bearing ready to rip through the bell housing.

[rand49er]

Really! Was the BMW driver alarmed at the noise ... I mean, was he going to get it taken care of?

Before the UUC FW install, my OEM throwout bearing was still fine, but I thought as long as it was opened up, I'd plunk down the buck$ and slap a new one in. Car had, like, 45.8k miles on it at the time; now has 46.1k.

[Kmajecki]

Originally Posted by perfect

lol, my car is like a symphony of funky noises, snaps, crackles, and pops

I've been running with my cutouts only open about 20% lately and have certainly heard many "new" sounds coming from many places. Awww a good excuse to leave them all the way open!


good luck with this Rand, sorry i couldn't be of much help. The only thing i've been feeling lately is when i start the car first thing in the AM and back out of the parking spot, i feel a little thump just before the car starts moving backwards, then i get another slight thump when i start moving forward. I back in 95% of the time I park though, so that is likely more of the reason i've never notice this before the axles

[darkman]

Originally Posted by rand49er

Really! Was the BMW driver alarmed at the noise ... I mean, was he going to get it taken care of?

Before the UUC FW install, my OEM throwout bearing was still fine, but I thought as long as it was opened up, I'd plunk down the buck$ and slap a new one in. Car had, like, 45.8k miles on it at the time; now has 46.1k.

I don't have constructive ideas yet but I am watching this thread.

Does this noise only occur in 6th gear? if not is it in all other gears? If yes, do you know another V owner in your area with a lightweight flywheel that you could test drive - just to see if it is simply the sound affects associated the flywheel that you are hearing. (My UUC, when "lugged" in almost any gear except 1&2, sounds a lot like engine pre-ignition/detonation except it clearly comes from the gear box rather than the power plant. Early manual Vettes sounded like this.)

[rand49er]

Originally Posted by Kmajecki

... i feel a little thump just before the car starts moving backwards, then i get another slight thump when i start moving forward ...

Yeah, I'm feeling that one, too. My thinking is that my drivetrain is getting so there's only one place for there to be slack: the diff. And I'm hearing and feeling it with every shift and also very noticeably when trying to hold a slow speed (say, 25 MPH) in my neighborhood while in third or fourth gear. If I back off a little bit or accel very slightly, the slack (or lash) in the drivetrain gives a heavy click or clunk sound. I think all of that is in the differential.

Making me think that CadiBlk and The Tony Show have very valid arguments that a lot of engineering went into these cars and by changing things we uncover problematic symptoms that we keep chasing and end up going in circles and never curing them. Doesn't mean it isn't fun, does it?

[rand49er]

Originally Posted by darkman

I don't have constructive ideas yet but I am watching this thread.

Does this noise only occur in 6th gear? if not is it in all other gears? If yes, do you know another V owner in your area with a lightweight flywheel that you could test drive - just to see if it is simply the sound affects associated the flywheel that you are hearing. (My UUC, when "lugged" in almost any gear except 1&2, sounds a lot like engine pre-ignition/detonation except it clearly comes from the gear box rather than the power plant. Early manual Vettes sounded like this.)

Glad you're tuned in!

I first noticed the really loud, bad sound after I was leaving my mechanic's house from having the FW installed. I was in 6th gear at about 35 MPH, something I've done numerous times. With just a bare minimum of throttle, the sound of preignition/detonation is very close to what I'd describe ... it comes right out of the transmission and is the sound of gear teeth not meshing well or not liking to be meshing. Seems like I've heard it in 5th, too, but not too sure about that. Since the shifter fork works between 5th and 6th gears, they may be both involved and transmit sounds together.

Darkman, it sounds very much like you've experienced this, too, from your description. Mine might be just a bit more pronounced than yours hence my whining here in this thread.

[darkman]

I think there is a real possibility that you don't actually have a problem, other than the noise itself.

As you say the noise level you have may just be more pronouced. That could be because of the Kars kit and the fact you may be have more aftermarket bushings that others. (I have the Specter Werkes cradle bushings but not the UUC differential bushing, transmission mount or motor mount yet).

6th gear in this car is actually a 2nd over drive since 4th gear is a 1-to-1 ratio which used to be considered "top gear." 5th gear is a 0.84-to-1 ratio, which is an overdrive ratio and 6th is a 0.56-to-1 ratio which is why I call it a "second" over drive.

I think gear noise from these ultra high gear ratios was the main reason GM went with the dual mass flywheel in the first place. Additionally, this gear noise is no different than that particular to the muscle cars of the 1960s and 1970s. It was not such a problem then because everything had 4-speed gear boxes with a 1-to-1 4th gear being the tallest gear.

Finally, I have read that Tremec blames 6th gear failures particular to the Tremec T-56 on drivers over using 6th gear in low speed situations which overloads the smaller components associated with that gear.

[Slithering_Joe]

Originally Posted by rand49er

Really! Was the BMW driver alarmed at the noise ... I mean, was he going to get it taken care of?...

No, they new what they were getting into when purchasing a lightweight flywheel. A heavy flywheel smooths out the rotation of the engine. Any oscillations will be heard in backlash of the drivetrain. In the cases I meantioned earlier, the most noise is heard in neutral at low RPM (idle).

[rand49er]

Originally Posted by darkman

I think there is a real possibility that you don't actually have a problem, other than the noise itself.

As you say the noise level you have may just be more pronouced. That could be because of the Kars kit and the fact you may be have more aftermarket bushings that others. (I have the Specter Werkes cradle bushings but not the UUC differential bushing, transmission mount or motor mount yet).

6th gear in this car is actually a 2nd over drive since 4th gear is a 1-to-1 ratio which used to be considered "top gear." 5th gear is a 0.84-to-1 ratio, which is an overdrive ratio and 6th is a 0.56-to-1 ratio which is why I call it a "second" over drive.

I think gear noise from these ultra high gear ratios was the main reason GM went with the dual mass flywheel in the first place. Additionally, this gear noise is no different than that particular to the muscle cars of the 1960s and 1970s. It was not such a problem then because everything had 4-speed gear boxes with a 1-to-1 4th gear being the tallest gear.

Finally, I have read that Tremec blames 6th gear failures particular to the Tremec T-56 on drivers over using 6th gear in low speed situations which overloads the smaller components associated with that gear.

This may indeed not be a "problem" other than the noise. The noise is horrible, though. But, like you say, it may just be a manifestation of the steepness of the overdrive ratio and the cut of the gear teeth and the less-forgiving nature of a lightweight FW.

If there are a number of 6th gear failures in Tremec trannys with drivers who drive like I do, then that is actually comforting, if you can believe it. Now, I have to decide if I want to spend the buck$ to put a new 6th gear in it, or just put up with the muffled sound. I intend to consult my mechanic.

Originally Posted by Slithering_Joe

... A heavy flywheel smooths out the rotation of the engine. Any oscillations will be heard in backlash of the drivetrain ...

That could explain why I hear so much more of the heavy click or clunk sounds from mine. Still, I do not hear that portion of the clunking attributable to the OEM dual-mass FW, and I definitely like that about the UUC FW.