Volvo Repair: 1989 240dl overdrive solenoid, mechanical skills, gearshift

Question
I have mechanical skills and there are over 200,000 miles on my 240 DL wagon.  The overdrive is engaged on the automatic transmission and I have already replaced the relay behind the glovebox to no avail.  How does one check the wiring and switch on and coming out of the shifter and can this be done without dropping the transmission?  Also, can the solenoid be replaced without removing the tranny as well if the switch and wiring appear to be ok?

Thanks!

Answer
Hello David,
           I'm not sure what your problem is...the O D stays engaged?..what does this mean?
         If you want to check operation at the O D put a hot feed to it...carefully routing wire...then road test.
          Wiring near the gearshift does fail.
           Good Luck,
                   Bilbo