Make sure that the front and rear sections of the driveshaft are aligned - there's an alignment arrow stamped on each, near the center bearing. If the misalignment is large, you'll get a driveline vibration at road speed. A small misalignment (like one spline tooth) can sometimes cause a low-speed vibration such as you describe.

U-joints, torque rod bushings and maybe tailshaft bushing are all possibilities, like the others said. But after changing your trans mount you may have changed some geometry of the driveline and now you need to shim the driveshaft. There was actually a Volvo TSB about this but I can find it. You need to sandwhich some washers between the center bearing crossmember and the bearing holder. Start with shimming 1/2" and then remove washers one at a time until the vibration is gone. good luck, I sure a well-titled post could give you some info on the actual TSB procedure.

Matt

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'82 DL - 153k, '93 945 - 102k

What about the two or three U-joints in/on the driveshaft? I'd second the opinion it might be the bushings. If you don't know when they were last replaced, you might as well.. as they're at least ten years old by now. But.. I suspect that a launch would alter the geometry of the driveshaft, and if the u-joints are cranky.. this could cause problems.

- alex

'85 244 Turbo
'84 245 Turbo

torque rod bushings are an inexpensive and easy fix. if your present trailing arm bushings have over 100k they probably need replacement.
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