My 94 slips out of first gear. will only stay in first if started in second then body put into first and held there under a load does anybody know what the problem is

 

I assume you are talking about a manual trans. If that is the case, then you have a bad 1st gear synchronizer. To replace this, you must pull the trans out of the truck and disassemble it. If you are going to do this yourself, many companies make inexpensive rebuild kits that include synchros, seals and bearings.