Volvo: overdrive, 1989 volvo 240, volvo 240

Question
My 1989 Volvo 240 on occasion goes into or starts in overdrive which i cannot disengage and then after about 20 miles it goes into 4th pretty quickly and drives normally after that.
any ideas would be appreciated thanks,
Patti  

Answer
There are several wires running from the over drive solenoid and the 4th gear sensor up through the hole where the shifter is.  Sometimes, those wires can flake and short together, causing random symtoms like engagements at the wrong time.  I would take a look at those wires, and replace them if necessary.  Good luck!