Jim, first thing. Can you share a bit more about your '48 GMC, What is the particular model, 3 speed or 4 speed.
RonR
Added in edit; ok, a search showed you've been working on the problem already. There are some very knowledgeable folks here, I'd continue to seek out advise and not give up to quick. One thing about today's shops is they don't have the generational knowledge to work on our trucks with any certainty. You need to find one with old geezers, lots of gray hair, possibly a pair of overalls or two and it doesn't hurt if there's a good bit of old oil soaked concrete in a lot of the shop.
Good Luck
RonR
Last edited by moparguy; 09/20/2019 1:27 PM.
