Chevrolet Repair: manual trany problem 4x4, chevy truck, synchros

Question
i lost 3d and 4th gear in my 5 speed 4x4 1500 chevy truck any help would be nice

Answer
Unless you have major knowledge in manual trannys, then I would strongly advise against repairing yourself.  There are alot of gears and synchros  and special tools you will need for this repair.  If you have lost 3rd and 4th, chances are the gears are stripped off the shaft inside the trans, and are just free spinning.  Repairing a manual trans is not an easy task to say the least, and even harder to explain in full detail how to repair, and exactly what tools you will need
Im sorry  I can't be of further assistance
Jimmy