1985 Ford F-150 transmission

Check to see if brakes are locking up especially if sitting a while that may be the cause. If not going forward and brakes are not the problem then you have a clutch pak hanging up in trans.

There are three clutch paks inside trans that are applied at different times. If one is burnt up or locked it will cause the problem that you are having. It may or may not break loose if you try to push forward an dit's not brakes stopping you from going forward. The only thing I can suggest is two things. Remove driveshaft and or back off brake adjustment on rear brakes. It could be parking brake was applied and cable has locked it up from going forward. If you remove driveshaft and it still won't move forward then it is brakes holding you up.

You might try it with two screwdrivers to stop from buying a brake adjusting tool. You'll have to find the hole in back of brake drum then move the screwdriver so the wheel in pic goes against the lever. See pic. One side will go one way and the other side will go opposite way. If you use two screwdrivers one will push lever outward so wheel can spin freely.