ok i have had this problem in 2 cars i have driven lately a R33 GTST type M and a VL turbo modded to about 300 RW HP in first and some times 2nd gear i get a weird very strong vibration like diff bounce the only weird thing is why would the cars start doing this when i have never noticed this befor under hard accelration?

Problems like that can be caused by bending of critical parts (under acceleration parts of the drivetrain might bend because of the high torque). When parts get older or reach the end of their lifetime bending can increase dramatically. So either some part just bends more because of fatigue and can live for ages this way or some part is about to fall apart and will soon die. I suspect the former.

Vain

what i meant is its feels just like the back end of the car is jumping of the ground as it trys to spin and comes back down again and then cause of the hard accelration it bounces again and again. i was thinking it has something to do with the LSD and the short hard springs in the 2 cars,ie maybe the diff's and suspension are going i know the LSD in my VL is going as its started doing 1 wheelers when drifting but the LSD in the skyline and VL are perficted under even weight to each rear wheel.

u sure its not wheelspin?

Yep, my old volvo 340 (ahem) was rear wheel drive and it skipped about loads at the rear when you spun the wheels up.

It was a combination of things such as the driveshaft, but it was mainly just due to the rear tyres and rear suspension skipping when wheel spinning. Leaf springs made it worse

Definitely sounds like wheel hop to me.

Best example of that is in Bullet when he missed the turn, and slams it in reverse...the wheel is hopping like Skippy then

A little offtopic, but my first car, a fwd Escort, sometimes jumped like hell when spinning wheels from the start (I don't call this a "burnout", because it would insult cars like this)

Yup, sounds like axel tramp to me. If you wanna solve the problem you can get panard rods which brace the axels longitudnally and stop the suspension moving backwards and forwards. Getting solid bushes may also stop it too as I'd imagine in your case you'll have the original rubber suspension bushes which are designed to filter out some of the smaller vibrations. They allow quite a lot of unwanted movement in high powered cars though so either getting poly bushes or just moving to metal bushes will reduce the tramping a lot

How cool is this! http://www.youtube.com/watch?v ... amp;search=saab%20burnout