Noizemaker

Earlier this month, pulling out in to traffic the S started moving and let off this horrible BOOM and then started grinding while not putting power down any time I was in gear.

Pushed the car, got it towed home. Trouble shot the problem, determined it was the diff had failed. Replaced diff. Put the car down tonight, and tried to pull it out of the garage... whereupon it started making the exact same sound again!

What the hell's broken? Here was my troubleshooting procedure.

Clutch out. In Neutral. No noise.
Clutch in. In Neutral. No Noise.
Clutch in, in gear, No Noise.
Clutch out, in gear. NOISE NOISE NOISE.
Rear of car in air, clutch out, in first gear. No noise, wheels move freely.
Rear in air, clutch in, in neutral. No noise.
Rear in air, Clutch in, in gear. No noise.

Based on it only being while I was in gear, we eliminated the transmission from contention. Figured the trans would make noise loaded or unloaded if it was an input shaft, etc... plus i distinctly hear teeth. Car starts fine, no wierd noises at startup, etc.

... so all that, new 20k mile differential. Still no motion, still massive noise. Ideas? Video clip in the AM so I don't wake my neighbors now.

Slows2k

It's got a broken CV joint.

Noizemaker

Really? That's the oddest sound ever... and sunuvabitch, i'ma be angry if i replaced a differential instead of an axle. I'll check it out. Any idea how to tell which one's bad? they both looked fine from under the car.

krikke_s2000

Rear of car in air, clutch out, in first gear,pull handbrake
and see witch parts are moving

grtz kristof

Noizemaker

I'll try that, Kristof!

For now, here's 2 videos of what it sounds like. For a sense of volume scale, the car is idling in both of them. Thats engine, not wind noise. It makes this sound in ANY gear i'm in, as long as i'm in gear.

http://www.youtube.com/watch?v=w7xgMds9bRU
http://www.youtube.com/watch?v=A1MYm83rdQk

Noizemaker

So with it in the air if you dump the clutch too quick, it makes the noise. If you slowly let it out, no noise, tires spin.

If you put your foot on a tire and add load. GRIIIIIND.

If you put the ebrake on. GRIOIIIIND.

I can't put the brake on and go check the rear of the car; I would need a second set of eyes as the revs/load climb faster than i'm comfortable with.

Videos incoming.

Noizemaker

http://www.youtube.com/watch?v=8-wuYbPacwQ
http://www.youtube.com/watch?v=hwQeI0tsofE
http://www.youtube.com/watch?v=Xi1UDK2ib8Y
http://www.youtube.com/watch?v=ys_4240ek2U

krikke_s2000

put the camera under the car when the handbrake is on then you can do it on your own and look to the fragment to see wath the problem is

grtz kristof

Noizemaker

I can only record fifteen second snippets, or that'd be an awesome idea.

.... hrm. maybe if my old camera is still floating around. Time to do some investigating.

Got under the car per a suggestion in the NW forum.

Car in 1st, ebrake off, one side at a time in the air. Moving wheel by hand.

RR in air:
wheel moves
Axle moves.
Driveshaft DOES NOT move.
Noise is made.

LR in air:
wheel moves
Axle moves
Driveshaft DOES NOT move
Noise is made.

I feel play in the driver's rear axle though. Wierd.

SgtB

You need to see if the output hub on the diff keeps spinning when you hold the wheel. If it is your cv shaft is toast. My bet is on the driver side joint.