Here's a breakdown:
Direct Bolt-On (or Relatively Easy Swaps):
* TH350 (Automatic): This is the most likely original transmission and the easiest swap. Finding one in good condition is relatively straightforward.
* TH400 (Automatic): A stronger automatic option, but might require a different flexplate (the part connecting the engine to the torque converter).
* 700R4 (Automatic): A four-speed overdrive automatic, popular for improved fuel economy. This usually requires a custom adapter or modifications to the bellhousing.
More Involved Swaps (requiring adapters or significant modifications):
* SM465 (Manual): A strong, durable manual transmission, but will require an adapter plate to mate to the 350's bellhousing.
* NV4500 (Manual): Another strong manual option, also requiring an adapter.
* T56 (Manual): A six-speed manual found in many GM cars, popular for performance upgrades. Requires an adapter and likely other modifications.
* Many other transmissions: Virtually any transmission can be made to work with enough custom fabrication, but this is a significantly more involved and expensive project.
Crucial Considerations:
* Bellhousing: The bellhousing on the engine dictates which transmission can directly bolt on. The bellhousing from the original transmission is likely still correct for a TH350 or Muncie, but you'll need a different one for many other transmissions.
* Adapter Plates: Many aftermarket companies make adapter plates to mate different transmissions to small-block Chevy bellhousings (which your 350 likely uses).
* Driveshaft: You'll likely need a new or modified driveshaft to match the transmission's output length.
* Computer Control (if applicable): If your 350 is using a computer, the transmission choice will influence the control system requirements. An automatic transmission requires a compatible controller.
Before you purchase a transmission, carefully check the bellhousing pattern of your 350 engine and the input shaft specifications of the transmission you're considering. Consulting a transmission specialist or a mechanic experienced with classic muscle cars is strongly recommended to avoid costly mistakes and ensure a proper fit.
