The OD system could have an electrical problem which will lock it out of reverse. The last one that I ran into that did that the owner accidently bumped the terminal on the govenor and grounded it out. Take out the inline fuse and take it out of OD. If it works you will need to trouble shoot the OD electrical components.
Fred

Note: This unit is designed to prevent the trans from being shifted into reverse while the OD is engaged. The solenoid may also be jammed into the pawl which engages into the blocker ring. You may need to remove the solenoid and check it out.

Last edited by rfs56trk; 02/13/2008 5:46 PM.

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine