RealOEM does not show the A5S325Z in my 325ci as being compatible with a 330ci, but I don't know why that would be. I'm sure someone will chime in with why the 325 and the 330 do not appear to share the same part number.

 

Yes, the gearing and TC may be slightly different, but everything will work fine. I have done many B25 to B30 swaps with both the GM and ZF auto trans and never had a single issue. The B25 and B30 engines bolt up the same.

 

First and foremost, thank you for the info and the prompt replies!

1. Is the "Transmission Sub model" (A5S325Z) marked anywhere on the transmission case?
2. Do I have to swap anything besides the trans and the torque converter, like the transmission control unit ECU?
3. Is it best to reuse my torque converter (from the 325) into the new 330 zf trans? Or should I use the 330 torque converter in the matching transmission?

 

Just swap the B30 engine in and leave everything else there. Will be just fine.

 

The 330 ZF has a different TC with a different clutch lockup.
The 330 ZF C clutch pack and housing are also different. The 330 has four steels and the 325 has 3.
The main valve bodies are the same, but the upper front valve body has one bore and piston different.
See this post for the details.

https://www.e46fanatics.com/threads/1311922/

As mentioned above, it will all bolt up and run, but there are definitely differences. Don't run a 325 with a 330 engine.