Well lets see here, number one your lucky the trans is one of the simplest built but with that said you definitely have something going on inside there that is not correct. Your lubricant in the trans was up to the correct level when you started having these issues? I would go under the truck and just look for anything that looks like it could be a problem or out of the ordinary, if all looks good you going to have to pull the tower off the trans (the top where your shift lever sticks out from) this will give you a pretty decent view of at least the top gear line and shaft also the shift forks they will be hanging down from the tower when you lift it off the trans. They should be straight and NOT bent or deformed THIS is going to be your first main thing to look over well. Then I would drain all the lubricant from the trans and start looking at the top set of gears and the shaft they ride on, again you looking for things that just dont look right or are broken, rough or possibly corroded. If you have a set of manuals read up on this procedure before you do it and if you dont I believe the TMs can be found on this site. If the shift forks are messed up they can be replaced with just the tower off the trans, if you find something deeper like broken or severely chipped teeth etc. your going to need to pull the trans to conduct those repairs, they are not hard to do but you cannot do them with the trans in the truck. This is your starting point you need to figure out just what is going on inside there, once that is done just get the correct replacement parts and fix it. Do not be intimidated by pulling the trans its easy to do but you will need a trans jack of some sort to lift it both out and back into the truck and have the TMs with you and read them before you get into this job. Feel free to PM me with questions. Karl
