Yup same thing happened to me about a month ago. It was the clutch master cylinder that crapped out on me. Now it could be the slave cylinder, but your experiencing what I did, and a new clutch master cylinder fixed it for me. They run around $50, more or less depending on where you get them. You can get a master cylinder/slave cylinder/line already pre bled, but I think they are pretty expensive. So go get yourself a new clutch master cylinder, DOT5 brake fluid (or whatever you master cylinder says to use). When you get it you are going to want to fill up the master cylinder before you put it in and bleed it by pushing in the rod thing a couple of times until a good amount of brake fluid comes out each time you push in the rod. The put it back in the truck and mount it. Next place the hydrolic line back in and secure it with the little thing that you hammer in there to keep it there. Next is the tricky part, you can either do it alone, or have somebody help you. If you have somebody help you get under the truck and loosen up the allen screw on top of the clutch slave cylinder (drivers side front of the tranny, the hydrolic line will go in it. If you have somebody help you I guess its just like bleeding brakes, have them push in the pedal and what not. Or you could do it with two people, except the extra person only fills the resevoir so it doesnt run out of brake fluid. First clean off the hydrolic line of all dirt so you can kinda see in it, trust me once you get going you will be able to see bubbles if cleaned good enough (I just used my hand and wiped off the dirt). Next loosen the allen screw and make sure you have a contaner ready to be placed where the brake fluid will land on the ground to catch it. Then push in the slave cylinder, like you would if you were to disengage the clutch, press it towards the back of the truck as far as you can and hold it there. It will be kinda hard to do, because you will only be able to use one hand to do it, because you will need the other hand to tighten up the allen screw on top of the slave cylinder when you get all the air out of the line. So just sit there with the slave cylinder in for a minute or tow, until you see no more bubbles going through the hydrolic line. Once you see no more, tighten up the allen screw, and all will be fixed. Just make sure you have an extra person filling up the master cylinder resevoir so it doesnt run out because you will have to do it all over again.
By the way it is not recomended to drive it, because it will hurt the syncros in the tranny.
