* SM465 4-speed manual: This was a common heavy-duty manual transmission.
* Allison 5-speed automatic: This was a popular choice for heavier-duty applications.
* 4L80E 4-speed automatic: While less common in a K3500 than the Allison, it's possible, particularly with certain engine choices.
To know for sure which transmission is in *your* specific 1996 Chevy K3500, you need to check:
* The owner's manual: This should list the transmission type.
* The vehicle's identification number (VIN): A dealer or parts store can decode the VIN to determine the original equipment.
* The transmission itself: Look for markings on the transmission case.
Without more information about your specific truck, it's impossible to say definitively.