You have to use a block of wood under the oil pan and jack it up only a couple of inches. If you jack it too much you can hurt the seal between the engine and tranny, not to mention your axle joints. Anyway, jack it up and inspect the different mounts shown here: http://www.fcpgroton.com/volvo850mounts.htm
The two big (non-round mounts) for tranny and under the timing belt area on the passenger's side are usually the ones that go first. I wouldn't worry about the circular subframe mounts. They're a bear to get to anyway and rarely go.
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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.