I have a 90 Silverado with a 350 5sp. Whever I pu it into 4th, it pops out of gear. Does this mean the synchro for that gear is bad? Does this mean the transmission might be on its last leg? If I pull the transmission out can just that synchro be replaced without too much effort?

 

manual trans are easy to work on if you pull it a part you will be able to see wht the problem is