have they ever been replaced? see the post from Don above for a bit more information.

if they've never been replaced, you're definitely due in. having an engine sitting too low is bad for a bunch of components in your car, including your drive axle and your exhaust.

for my 90 740, i picked up the mounts for about $68 a piece (you need 2) i believe fcpgroton has it for even cheaper than that. i think you need the hydraulic ones. don't get the wrong kind (solid rubber)

if that doesn't help the vibration, that's okay, you didn't really 'waste' any money since it's a 95% chance that you were due in for a change anyway. :-)

i had my mechanic due it for about an hours worth of labor, which isn't too bad.

another way to check to see if you do need to replace it is to look at the position of your engine's fan relative to the fan shroud (the surrounding plastic thing that it sits in) if it's not roughly in the center (too low) then you need to replace the mounts

if it's rubbing or there are rub marks on the bottom of the shroud, then you definitely need to replace it (the mounts)
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'