Robert, have you read thru the Service Manual for the overdrive transmission? It has some troubleshooting steps, and an explanation on how it's supposed to work, as well as some adjustments of the relay, which might be part of your problem with the fuses blowing. The solenoid has a pull-in winding and a hold-in winding with internal switches. If those are not working correctly it could cause high current for long enough to blow the fuse.
Here's the section on the Overdrive Transmission from the 55.2 Truck Service Manual.
Hope that helps. The circuiting is a little complicated to figure out without some explanation, which the manual has.
