Aftermarket/Non-Factory Transmission Options
Here are a few other transmissions that have worked pretty well before with a 3800.
Keep in mind if you're doing a swap, especially with a manual trans, that there are quite a few different flywheel/flexplate options that you could have on your 3800.
More information can be found about that here: Flexplate and Flywheel Options
Front Wheel Drive:
4T80e (4 speed automatic)
Getrag 282/284 (5 speed manual)
Getrag F23 (5 speed manual)
Getrag F40 (6 speed manual)
Muncie 4 speed (Fiero) (4 speed manual)
Rear Wheel Drive:
Tremec T56 (6 speed manual)
THM250/THM350/THM400 (3 speed automatic)
Other Potential Transmissions
These are transmissions that are not as well documented or have not been attempted yet but look promising
Rear Wheel Drive:
Disclaimer:
Use this information at your own risk, this may be incomplete or lacking in some areas. This has all been compiled with information gathered from many different sources across different forums. The information here is only as good as its source.