* Bellhousing Bolt Pattern: The 350 small-block Chevy engine has a specific bolt pattern on its bellhousing. The transmission you choose must have a matching bellhousing. You might need an adapter if the transmission's bellhousing doesn't match.
* Input Shaft Diameter: The input shaft of the transmission must be the correct diameter to fit the crankshaft pilot bushing of the 350.
* Gear Ratios: Consider what you want the truck to do. A lower gear ratio will give you better acceleration, while a higher gear ratio will be better for fuel economy at highway speeds. Think about the intended use of the vehicle - off-roading, towing, daily driving, etc.
* Transmission Length/Tunneling: Some transmissions are physically longer than others. You might need to modify the transmission tunnel in your S-10's floor to accommodate a longer transmission.
* Clutch: You'll need a clutch that's compatible with both the engine and transmission. This includes the correct diameter, pressure plate, and throwout bearing.
Popular Choices (but require research for specific application):
* SM465: A strong, durable four-speed manual transmission commonly used in heavier-duty applications. It's often a popular choice for swaps like this but can be quite physically large. Requires adapter housing often.
* NV3500/NV4500: These are five-speed transmissions from GM trucks that are relatively common and readily available. NV4500 would be more durable but heavier. They might require adapter housing depending on the year and model.
Before you buy anything:
You absolutely need to do your research to ensure the specific transmission you choose is compatible with your 350 small-block engine and your year/model S-10. Transmission swap details can be model-year and even engine-variant specific. Look for information specific to your truck's year and the particular 350 engine you're using. Online forums dedicated to S-10s and Chevy small-block swaps are an invaluable resource.
Failing to account for these compatibilities can result in a significant amount of extra work, expense, and potentially frustration.
