850 is 5cyl FWD.

940 is 4cyl RWD

960 is 6cyl RWD - same engine as S80 (but very differently configured)

Late model 960s (97-98, 98 was renamed S/V90) are extremely desireable if you like RWD. By 96, all the goodies that were in the 850's finally arrived in the 960: factory fogs, cd players, winter package, tracs, restyled interior, lower profile headlights. All these were added to what was always there: best (heated) seats in the automotive world, power moonroof, vast interior, heated mirrors.

(900's originated as 700's, and the renumbering was never sufficiently explained. In 1993, Volvo was making 240's, 700's, 900's and 850's. A marketing muddle.)

The old 86 240 rusted off its frame at 269K. My 88 745T went 278K before I sold it (no rust). My 94 945T went 170k before I sold it (spotless, utterly reliable, what a car). My 940GLT is running strong at 165k and showing few signs of age. My S70 is a baby at a mere 85K miles.
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)