Will a 1999 s10 blazer transmission fit Chevy s-10?

Not necessarily. While both are S-series trucks, the transmission compatibility depends on several factors, including the engine size, the type of transmission (automatic or manual), and the year of the S-10. A 1999 S10 Blazer's transmission *might* fit a Chevy S-10, but it's not guaranteed. You need to verify the specific transmission model numbers (found on a tag on the transmission itself) for both vehicles to ensure compatibility. Even with matching numbers, there might be minor differences that require modifications. It's best to consult a repair manual or a parts specialist for accurate compatibility information.