Rear Clunking Sound after new gears and Driveshaft

[JM10]

Car is making a weird clunking noise (metal) after new diff with 3.91 gears, diff bushings and DSS aluminum shaft.
it happens mostly on 1st and 2nd gear also when pressing and releasing the gas pedal.
I know M6s have a "normal" slack in gears, but this sound is way more louder...:(

Help please

Video:
http://youtu.be/-thkw1qO0PE

[Doc]

Check to see if the flange bolts at the rear of the driveshaft are hitting the top of the cradle frame just above them. With the amount of horsepower you're pumping out the rear moves quite a bit when you apply power. You may need different bolts/nuts if they're making contact and/or heavy duty differential bushings to cut down the amount of flex and movement.

[JM10]

Originally Posted by Doc

Check to see if the flange bolts at the rear of the driveshaft are hitting the top of the cradle frame just above them. With the amount of horsepower you're pumping out the rear moves quite a bit when you apply power. You may need different bolts/nuts if they're making contact and/or heavy duty differential bushings to cut down the amount of flex and movement.

It sounds like there is a play somewhere between the driveshaft and the differential. It only happens when the trans is not under load.
Even when slowly taking off from a stop you can hear the "clunk" ...

In the video I was short shifting on purpose ..

[Doc]

Again, check the bolts. If they're sticking out too far the clearance is VERY small so even a small amount of flex can cause the bolts to contact the top of the crossmember. I've been one of Frank's testers when he's been developing these driveshafts and this was a problem.

If there's contact you'll see it on the bolts and the top of the crossmember will be shiny where they've been contacting. The sound is tricky because it transmits through the shaft and makes it hard to isolate where it's coming from but the video sure sounds like bolt contact. It's not constant; it's on and off like the sound on your video.

Look for contact marks of any kind on the driveshaft and the bolts near the differential.

[JM10]

Thanks,

I will follow your advice and let you know.

JM

[JM10]

You were right!

The bolts were loose (not touching the cradle) ......one of them I was able to move it with my hand

Now after tightening all of them everything is perfect, thank you very much!

JM

[Doc]

Originally Posted by JM10

You were right!

The bolts were loose (not touching the cradle) ......one of them I was able to move it with my hand

Now after tightening all of them everything is perfect, thank you very much!

JM

Cool, glad to hear the problem is fixed.