* TH350 (3-speed automatic): This is a very common transmission for that era and engine. It's a likely candidate if your truck had an automatic transmission.
* TH400 (3-speed automatic): Another strong possibility for an automatic, although perhaps slightly less common than the TH350. It's generally considered more durable.
* SM465 (4-speed manual): A popular manual transmission option.
* 700R4 (4-speed automatic overdrive): Becoming more common in later 1980s trucks, but it's possible your truck had one. This requires a different transmission control module and potentially some other modifications depending on the original setup.
* NV3500 (5-speed manual): Less likely for a 1985 model, but possible depending on the trim level and options.
To determine which transmission fits YOUR truck:
1. Check the truck's VIN: The Vehicle Identification Number often contains information that can help identify the original transmission.
2. Look under the truck: The transmission casing usually has markings indicating the transmission type.
3. Check the owner's manual (if you have it): The manual will specify the original transmission.
4. Consult a Chevrolet parts catalog: Use the VIN to identify the original specifications for your truck.
Once you know the original transmission, you can determine what other transmissions will fit. While some transmissions might be *bolt-on* compatible, others may require modifications to the driveshaft, crossmember, and possibly the engine mounts or wiring. Always check for compatibility before purchasing a used transmission. A mechanic specializing in classic trucks can be a valuable resource in this process.
