F250 Overdrive problem

I have a 91 f-250 4 x 4 auto with electric overdrive. I have a problem with the trans and overdrive. I have lost all power with the trans when the OD is on, but if I switch the OD off, it runs fine as a 3 speed. I heard that it might be the shift body and probaly a seal for the OD line which is different from the 3 speed line. Anyony able to shed some light on my problem..

Thanks