Volvo Repair: 89 240 DL auto overdrive slow to engage, gas milage, solonoid

Question
Hi.  I recently acquired a 1989 240 DL sedan, automatic transmission and encountered problems with the overdrive.  At first the Overdrive Disengaged light (up arrow on dash) would go on and off at random, or just stay on.  I replaced the relay behind the dash and now the light turns on and off with the switch on the shifter.  That being fixed, I've encountered a seperate problem.  The overdrive won't engage until you've driven the car at least 20 to 30 minutes.  I've driven the car enough to discover it has nothing to do with speed or driving conditions (i.e. driving around town then on the highway versus all highway driving), after 20 or 30 mins when you reach highway speed the overdrive kicks in.  I've not driven the car when it was functioning correctly, and this is my first Volvo, so I'm not really sure what "normal" is for this car.  As such, I have two seperate questions:  1)  What might the issue be, and how to repair?  2)  Will it hurt the transmission to drive the car?  I drive about 50 miles/day combined city and highway (45/55% respectively).  I would keep the speed to 55mph highway.

Thanks for your help, Steve.

Answer
Steve, You can get another Solonoid and try it and see if that helps but in my experience, It turned out to be an internal problem with the transmission.  How bad is the trans fluid?  You may want to try a drain and fill a few  times to get it nice and red again.  It wont hurt the car to drive it but gas milage will suffer. Roger