* 4L80E: This 4-speed automatic was a very popular choice.
* Allison 1000: This was also a common automatic transmission, particularly in heavier-duty applications. The Allison was known for its durability.
To know for sure which transmission is in a *specific* 1997 Chevy one-ton truck, you'd need to check the vehicle's identification number (VIN) or look at the transmission itself (it usually has identification markings). The owner's manual would also specify the transmission.