A friend of mine brought me his early 4-lug 850 because his car has neutral for all his gears. My first thought was maybe the slave is stuck, but who has ever heard of that. I've never worked on an 850 before, so who knows. Turns out that the slave overextended, blew the seal, damaged the seal and the clutch was stuck disengaged. After some reading online (I couldn't find any Volvo specific issues) it seems that an improperly setup clutch fork can cause this, but most of the time that happens the first time you go to use it. Last year this car had the clutch slave replaced (it got stuck at a shop that closed down and then went across the street to another shop who didn't specialize in Volvos, but they did the work). When it was replaced, the mechanic said something like it's probably going to need replacing or somethings stiff not right. I wasn't involved, so I don't know exactly. But from my arm chair, it sounds like the clutch fork is probably to blame. Maybe it's work badly, or a clip fell off. Just looking at it I couldn't tell. It looks like the fork is too large to slip out the hole so the transmission probably needs to come out. I figured I'd see what you guys know fixing the fork.