Hi,
My GMT400 is 1998 C3500 SRW 6.5TD, I'm pretty sure it's fitted with a GM 14 bolt with a 4.1:1 ratio.
Its currently has an open diff and I'm looking to fit a TrueTrac but there are three available for the 14 bolt.
1. How can I tell (ideally without pulling the rear end apart) if it is a...