89 f150 will not go all way into rev when using shifter take cover off and removed shifter and forks and can manually push it into rev and it stays in put shifter back and same issue

The trans should be in neutral , if you look down inside the shifter tower the shift fork lands should look like this [ ] not like [
].

If this is a manual box then the problems can be loose gear box bolts, incorrectly tensioned bell housing bolts, spigot gearing failure in the input/ out put shafts or bearing failure for both shafts. After removing the shifter turret check the operation of the shifter rails as it may be a faulty selector fork ( both gears are controlled by the same fork)

insufficient battery power to stay running. replace battery or alternator.

MANUAL OR AUTO?

possible worn shift fork or shifter you can take the top a part and see if the plastic ball inside is not worn but thats all its a big job to remove trans for internal repair try to remove inside cover and shifter then 4 bolts holding cover shifter to trans and pull it out you have shifter in hand now look at the trans shift forks are they worn or ok and the teflon bushing on the end of shifter is it worn or cracked

Remove the rubber mat or carpet from the floor around the shift tower. This will expose a stamped steel plate that you can remove to get access to the top plate of the transmission. Place the transmission in neutral and remove the bolts securing the top cover to the tranny. After removing the bolts you may need to use a rubber mallot to bump loose the cover. Pick the cover straight up and out. After removal cover the hole with a rag or better yet fabricate a cover from a thin piece of plywood that you can bolt back in place with a couple of bolts to prevent dirt and foreign particle from entering the tranny. When you remove the top cover and see the forks hanging from the underside don't worry. When you place the cover back onto the tranny just line up the shift forks to the slots they drop into on the gears. Piece of cake.

tran out of gear,pull back floormat,remove bolts on large cover.remove gear selector bolts.pull straight up and out.check the forks and see if damaged.you can move the gears around and find the trouble.This is the last year 89 that you can do this.

You have a broken retaining clip in side the transmission .These hold the shifting forks as well as the gears in the correct positions . Drain the oil from the transmission you will see the broken clip

I guess what you have is a 5 speed trans. you'll need to remove trans, remove stick, drive shaft, linkage, after you have trans out, remove top cover on trans, fork will be connected on cover, remove slide pin that holds fork and install new one, refill with manual transmission fluid.takes 1.75 qts.hope this was very helpful, good luck. Not as bad as it sounds.

make sure shifter forks are lining up were they go? they fit into slots on the synchro/gear housing? and the cover has dowl pins to line it up ? autodoc