Hi, what is most likely the cause when the car vibrates BAD when accelrating, mostly in 4 or 5`th gear(automatic)71000 miles?
i have read this is a problem, but dont know the possibly cause, or what part that go bad.
thanks

Could be upper engine mount/stabalizer. The one that is in the ring, coming off of the fire wall. Look under your hood and see if there is any play in there or if the rubber is disentegrated.

Can you tell us if it's on the driver's or passenger's side? if it's one or the other, then it could be a bad axle shaft and not the above mentioned issue, or it could be out of balanced tire(s).

But then again, with your car being AWD (is it?), it could be the drive coupling that sends the acceleration to the rear wheels.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.

Hi thanks for reply, its not engine mounts, i had a bad upper engine mount on a 850 fwd before, but that was more like a noise, i didnt notice much while driving, other than a knocking noise, this viberation is real bad, it can be comperred with a bad axle shaft joint on a 300000miles volvo 240rwd, but even worse, this is a awd xc70, you mentioned drive coupling, i guess that is in the middle of the car somewhat, that can be the place to look, how about the 4wd coupling? i think the vibration is locationed from middle of car and back to rear driveshafts, i firsts thought about the transmission, but its futher back than that.
thanks

Yes, I mean the 4wd coupling. They changed the name of this. It was first bevel gear, then viscous coupling, etc. That's what I meant.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.