I have a 240 station wagon from 1991. it has 260 000 miles and ran like a champ until last week.
It is now running all the time as a 3 speed instead of a 4.
By reading some of the posts, I understand it is a common problem, but I am very new to the whole thing and need some clear indications on where to find the OD relay and solenoid (some description of what they look like would also be appreciated)

Thanks a lot.