Are the guts interchangeable among all 5 Speed casings, 77-83?
My situation: My 78’s transmission was overhauled over 20 years ago using a ZX trans. All indications externally point toward an 81-83 ZX doner that was used. I’ve been able to identify it, but the revs in 5th don’t add up to a close ratio when I plug in the numbers to an online simulator. The original 3.54 differential is still in the car. I’m wondering if the shop used a rebuild kit for a 78 and only the casing was intact from the later transmission. Is this possible? At 60mph the car’s tach reads around 2500 which sounds like the gear ratio of the 77-79 transmissions at .864, as opposed to .745 for the close ratio. I’m baffled what’s really inside my transmission without tearing it open and counting teeth. Pictured is the simulator that does the math. It lines up to what my car’s tach reads.
I had the same transmission rebuilt three years ago and I’m still not sure if it’s a close ratio. Recently, I installed the proper shifter from an 82 with new bushings, which made a huge difference. Anyway, I know this all sounds confusing, but the question is simple.
Thanks!