In article <email@example.com>,
> My Volvo will not go into overdrive. The overdrive light does go on and
> off so I think the switch works. I am assuming that the solenoid is bad
> or the relay is bad. What would be the proper way to diagnose this
> problem. Thanks for any help.
Look for a round single wire plug under the car, on the passenger side
at the rear of the transmission. With it unplugged the transmission
should shift into overdrive normally. The odds are about 3 in 10 that
the solenoid is at fault. The other 70% of the time there is a problem
in the valve body in the transmission, especially if the fluid hasn't
been changed regularly or has gotten low. There are several nylon check
balls the float up against the separator plate in the valve body that
can erode away to nothing over time when the fluid is carrying a lot of
The goal when driving is to miss the maximum number of objects.