Numerous possibilities in the driveshaft. Most were mentioned, but get under the car and check out the tailshaft bushing play (side to side play). I've seen some REALLY bad ones--all owners complained about shudder upon starting from a complete stop.

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Chris Herbst
1992 945, 71k
Volvo shop tech

I just replaced the carrier bearing and related bushing on my driveshaft and it cured my car's vibration at high speed and partially cured the problem of the driveshaft bumping the bottom of the car when loaded and accelerating from a stop. However, I think it will take a little more fine tuning to completely solve this problem.

There was a lengthy discussion of this not too long ago. Apparently there's a TSB related to this problem that outlines a method for fine tuning the driveshaft alignment.

Read this:
http://www.brickboard.com/RWD/index.htm?id=449299

and this:
http://www.brickboard.com/RWD/index.htm?id=454730

and this:
http://www.brickboard.com/RWD/index.htm?id=451826

There may be more that are useful. Do a search for driveshaft shudder or vibration. Let us know how you fix it.

Don Tibbetts
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92 745T 93K mi

Look in the archives this forum at my post of March 24, 2002 titled "960 driveshaft shudder". There are a number of responses that will give you most of the information you're looking for. Ringlee responded with the following, which I'll repeat here. You can find more under my original posting:

"Make sure you check out this Volvo TSB:

Driveline Take-Off Vibration: Shimming May Be Required. From Volvo Technical Service Bulletin 45/102 Jan '91. [Symptom:] Take-off vibrations at low speed, especially with high acceleration and/or heavy load, can occur in some cases. [Solution:] The level of vibration can be reduced by changing the vertical position of the center support bearing. Best results differ from car to car. Start with a change of 6mm (1/4") upwards. If results are not acceptable, try positions from 5mm (3/16") downwards to 12mm (1/2") upwards from the original position. Note that clearance between drive shaft and fuel lines must be at least 20mm, and between drive shaft and the fuel tank at least 16mm. Shimming upwards should not exceed 12mm (1/2") and after re-positioning the center support bearing housing should not contact the floor pan. "

BTW, I adjusted my support bearing and solved the problem. FWIW, if you decide to remove the drive shaft for any reason, be sure to not only mark the relative positions of the shaft to the flanges it bolts to, but also keep track of which bolt goes in which hole. Volvo used bolts of differing lengths where the shaft flange bolts to the pinion flange in order to ensure a proper dynamic balance. If you swap the six bolts around, you may upset the balance.

Good luck...