Strange noise from 2000 Camaro LS1 A4 drivetrain.

[emarkay]

Have an unususal noise from the drivetrain. It starts at about 45 MPH and gets louder (but with no change in frequency) as MPH increases. It sounds like a dragging brake or a vacuum leak, but it is strictly MPH related (not RPM). The faster one goes, the louder it gets, and in coast or drive, and engine off or on; it stays the same.

The Tech used an acoustic noise finder and it provided no clues while driving. By putting the car on a lift, and running it in gear, the sound seems to come from THE MIDDLE OF THE DRIVESHAFT, and it is LOUD! The U-joints were inspected, and I just had the differential pinion bearing replaced due to it's failure, and a new axle and all other differential bearings were replaced at that time, but the noise started BEFORE this work was done.

There is some faint bearing noise at the tranny tailshaft, but a pan inspection showed normal wear debris and no bearing or bushing residue. What about the transmission oil pump? There are no codes being thrown, nor any shifting issues?

The car has 86K miles and is stock and has not abused. Tires have been rotated and pressures checked, and no evedence of dragging brakes or other related problems.

What about the propeller shaft? Could a balance weight have fallen off? Would rotating the shaft 180 degrees assist in diagnosis? Can the GM EVA tool pick up acoustic noise, as there is no apparent vibration?

What about this torsional rattle that is mentioned in the shop manual? Google does not offer much help on this.

Also Curious as to what could EFILive's BIDI or reflashing capabilities offer as a diagnostic tool to assist? (A real world problem here...)

Any other ideas?

THANKS!

MRK

[dissonance]

A easy way to see if it's the rear or related to the rear might be to pull the drive shaft off and see if you can hear anything while it's off, I do remember your car having TC so that might cause some problems, disabling it might keep everything working normal while the drive shaft is off.

I have not delta with a problem like this before, but I do know a little about the 4l60e -rebuilding one not to long ago

If your home tomorrow and would like to talk about it more I can give you a call, just PM me your number, “I still have it but I just moved and I don’t know it’s location at this time.

*Edit, thinking about it a little more... Could be the rear end tolerance problem, gears… maybe something else

[joecar]

Transmission pump is at front of trans and would make a RPM related noise, so that wouldn't be it.

If DS lost a weight it might flex like that and make a noise.

Grab yoke that fits into rear of transmission and see if it has any up-down or left-right movement.

[joecar]

Could your DS have gotten slightly bent in the wreck someone inflicted on you...?

[emarkay]

Yea, but it doesn't sound or feel like an out of balance condition. Dissonance, will call you later - you have my # now. I need to think a bit more on this one.

[Garry]

Got a similar problem - though, with mine it starts somewhere around 10mph or so ...
After replacing the rear wheel bearings, we got smart and ran it on the lift (if you do, remember to turn off TCS ) - the tech guy said it sound like it came from the differential housing, but the diff itself should be fine, when the bearings were replaced I took a look and didn't see any major sign of wear or tear ... so, at the moment, my guess is the bearing where the drive shaft goes into the differential ... there is a TSB out there about a problem with DS noise ... got the number (140801), can't get ahold of the actual TSB ...

[emarkay]

I seem to recall that one from 2001 and I believe it addresses the Torsen noise, and advised it is normal. All those bearings (pinion, 2 axle and 2 wheel) have been replaced. Did not notice and visual runout on DS. Will be looking at it today.

Thanks for suggestions - keep thinking!

[joecar]

... there is a TSB out there about a problem with DS noise ... got the number (140801), can't get ahold of the actual TSB ...

Garry, do you know the date of this TSB...?

[Garry]

Will this info help any?

http://www.carcomplaints.com/Chevrol...001/tsbs.shtml

[joecar]

Ok, good, NTHSA says AUGUST 14 2001...

I punched in 140801 in my SI service manual and it couldn't find the TSB, so I'll have to manually find it using the date (tonite).

Thanks.