Odd driveline vibration in 1st/2nd when torque hits

[JCviggen]

Since my gearbox was rebuilt last year, the car has a strange vibration when going from a stop or slow speed in 1st or 2nd gear. It only lasts for a very short time, half a second in 1st and maybe a second in 2nd gear tops. It occurs when the turbos start producing torque and you get that initial kick in the back. It's almost a crunching sound, but dull and there's not really a metallic sound to it. But I can feel it through the seat, feels like it's coming from the center of the car but it's hard to pinpoint.

It seems to be more pronounced when the car is well warmed up after a bit of driving, and it's much worse if I happen to have some steering lock on / not going in a straight line.

In a straight line, i'll only get it very briefly in 1st gear and not at all in second. When turning, it will do it pretty bad even in 2nd (e.g. at a junction rolling in 2nd gear into the turn and getting on it before the car is straight)

It's been doing this for over a year now, and it hasn't gotten any worse, no change in behavior as far as i can tell. But it didn't do it before the rebuild (had the usual TC clutch failure)

ESP/TC on or off makes no difference.

I've asked around and nobody I've talked to has any ideas....so I figured I'd ask here where there are quite a few people with these cars.

Here's a video (was not tuned yet) you can hear it (barely) just past the 3 second mark just before 4000rpm in 1st) http://www.greenringer.net/various/shudder.mp4

[JSRS6]

Check your trans mounts and your prop(center) shaft carrier bearing.

[Elevens]

When was the last time your CV Joints were replaced? I had all kiinds of noise and Vibration issues with my Allroad a while ago. I could not pinpoint the source. So as a first resort I replaced the front shafts and joints. Instantly all noises and Vibrations were gone. May not be your issue, but it's a fix that has been known to solve a lot of driveline noises........................

[JCviggen]

Thanks!

No idea on the joints, may never have been replaced (car's at 77k now)
I don't have any unusual noise or vibration when turning (aside from full lock but it's always had that a little bit) only in high torque conditions.

[TozoM8]

Sounds like front axles or the front diff.

[JCviggen]

Knowing my luck (and this car) it's going to be expensive!