Zen of Volvo 240 Wiper Linkage:

http://www.jimjmorris.com/cvcoa/wipers.htm

The wiper shaft comes out of the mount/bushing from the inside but you have to remove the linkage and cable. I don't recommend doing it as I had a hell of a time getting it back together. The linkage comes apart by loosening the little cable locknut on the drivers side. Installing requires a small screw driver into the slot in the end of the cable while tightening the locknut. All this while sitting upside down with head under dash and between peddles.

Try lubricating the wiper shaft from outside after removing the wiper arm and rubber seal. The motor gears are plastic so don't stress them too much.