Volvo: AWD driveshaft problem, rear axle shafts, rear drive shaft

Question
I there,

I had a similar problem as the case below and my mechanic told me your front to rear driveshaft was broken... and it,s 1500$ to repair. So I was wondering how hard could it be to ask a shop to refurbish the driveshaft and change it myself. (Me and my buddy are actually working on a motor swap. So we do have knowledge in mechanic.) As the case below explain: vibration (very rough) occur only between 32 mph to 37 mph. After that it's a very small vibration, more like a hummmmmm. There's the problem. Thanks for the answer.

Antoine   
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Question
Thanks.  Only vibration is when moving and only at those speeds though as it gets worse it expands more. Seems if the problem were the rear drive shaft (connects rear differential to trans) that something would have been different when it was changed or balanced.  Therefore I think it may be in front or rear axle shafts or CV joints.  Could one of them be dry and binding or out of balance?  Or could it be a front or rear motor mount that is soft or collapsed so that under just the right combination of speed, motor angle and so forth that this hard but small vibration sets up?
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Followup To
Question -
My 98 V-70 AWD with 166,000 has been developing a dull vibration (like a frozen U-joint in an ordinary rear wheel drive car) during the last 30,000 miles and recently gotten much worse. Ocurrs at 32-35mph and 63-68, at times more pronounced than others.  During this time I have run three different sets of tires, always same vibration. The drive shaft was replaced with a used one (bad center bearing) but no change in vibration.  Volvo mechanic replaced "drive shaft balance bolt", no change.  A different Volvo mechanic at another shop replaced the right motor mount - no change.  He thought it was not the bevel gear because there was little noise. There is no clicking in CV joints.  There is however a swishing or sloshing noise when the car is in gear at idle, but transmission works perfectly, always has, no repairs ever to engine, transmission or driveline except above.  Original suspension parts, struts and self-leveling shocks.
Stumped!
Answer -
Well the only thing I could think left is the main engine mounts.  The right side one is for balance only.  I have had several XC90's and XC70's where the car runs great but has this vibration that you can't seem to pinpoint.  It has usually been the front and rear engine mounts.  Kinda of a pain to change, even with a lift because of the subframe design on this car.  Usually you can feel it at idle with this problem though.  Is your problem only when driving?  It could also be the driveshaft itself.  I have had several go out of balance and it is ALWASYS the hardest type of vibration to locate because there is almost no way of telling it is the right or left side.  If it is an axle though it will feel fine at idle or coasting but will start vibrating again once you get into the gas.  Hope that helps.

James

Answer
Antoine,
It appears that the problem is in the front driveshaft, so if it were replaced using a new or manufactured one the problem would be fixed. Now where do you a shaft made, that would mean finding a shop that can make a driveshaft and fit it to your car... Can't see why that would not work.