So I bought this 59 half ton with a 327 of questionable origin and ancestry. The kid said he thought it was from a 68 Impala and he couldn’t remember where the transmission came from. I don’t know anything about how to tell what type of transmission I’ve got, plus it’s covered with about an inch of grease and crud all around. It’s a truck 4 speed and it pops out of 2nd gear. I’m looking for advice on the transmission. Should I try to find someone to rebuild it? Should I go to my local bone yard and see if they can give me something that will work? What kind of interchangeability do manual transmissions of the possible vintage of this thing have? I haven’t really done any serious mechanic work other than a VW Beetle for about 25 years so any advice or insight will be greatly appreciated. Stan
What you most likely have is an SM420 4 speed. It has what is known as a Compound low ( 1st) gear which is usless for everything except crawling up the sides of buildings, or pulling stumps out of the ground. It's a GREAT truck trans, but leaves a lot to be desired when it comes to cruising for gas milage. From how you describe your experience, I'd recommend that you look into having the trans rebuilt/repaired. Popping out of second is a classic sign of a bad syncro. Other than it weighing about as much as the V8 engine that's in there, removal and installation is an easy job for a good trans shop. ( That place that has two A's in their name is not the first that comes to mind.) Be prepared to replace the clutch and pressure plate and throwout bearing. With the trans out, NOW is the time to do that ! Val
