I have two transmissions that are similar to the 12a transmission out of my 1983 GSL but differ in these ways. 1. each has a vent on the bellhousing 2. one of them has ribs on the bellhousing and the other is basically smooth. Because these transmissions came from buying project leftovers the exact applications were never made available to me. I am pretty sure they are 13b parts but would like to be able to identify if they are first gen or second gen. Either way are they compatible with the 12a. Are there specific markings to look for or reference photos on the site that as a newbie I have not found yet? any help would be appreciated.

 

Post a pic. The one with a vent but no ribs is probably a 1984/1985 GSL-SE 13B trans. Will work great on a 1983. Both of these trans have a 225mm clutch disc. The 1983 trans is also a 225mm clutch disc. Verify with the flywheel on the engine. The flywheel will have a big number on it that will tell which version it is. The clutch disc needs to be match to the flywheel.

The shifter is a little of between the 1984/1985 and 1983.

The ribbed trans could be an early 13B that would also work and have the shifter in the correct location. A picture will tell us.

Verify Flywheel Here

 

Thank you for your response. I will use the information that you supplied and do some more homework. I am not very computer savvy but I will try to post some photographs.