Just bought a 1994 Toyota Pickup. The owner said one time it popped out of gear. Whenever I try to put it in 4th it feels like it goes in but when I release the clutch it just grinds like it's not all the way in but I can't push it any further.
Any ideas what's wrong?

 

The dog clutch teeth are probably worn on the syncro or the main drive gear itself.

 

Yea, it certainly sounds like that gear is gone.

 

Not sure if this will change anything but I did just notice today that it's not going all the way in. It's as if it's hitting something.

Also the truck is lowered 3 inches