There are many different variations of the Borg Warner T10 four-speed manual transmission, because from 1957 to 1987, every American vehicle manufacturer has used the T10. The T10 is a reliable transmission that continues to be used in a variety of restoration and replacement applications. The two major classes of the T10 are the early cast-iron unit and the aluminium-cast Super-T10 -- all of which can have different gear ratios. Basic identification is simple. However, determining the different gear ratios of the T10 requires the transmission to be off the vehicle.
Look at the transmission from the driver's side of the vehicle by going under the vehicle at the driver's-side door. If the transmission is off the vehicle, it is on the left side, when looking from behind the unit and the input shaft is pointing forward. An aluminium cover where the shifter linkage attaches to the transmission is bolted to the side. Borg Warner T10 transmissions have a nine-bolt side cover.
Look for casting identification on the transmission casing. According to Drivetrain.com, the "T10" designation and the code, "13-04," is sometimes cast on the transmission housing.
Count the cross-grooves on the input shaft. The input shaft enters the engine at the front of the transmission. Since there are many gear-ratio variations of the T10, there are identifying grooves cut across the clutch spine of the input shaft. According to Drivetrain.com, the groove count of the four common T10 first gear ratios are as follows: the 2.43 first gear ratio has two grooves, the 2.64 first gear has three, the 3.42 has five and the 2.88 first gear ratio has six. The gear ratios ultimately identify the T10 in question.
The cast iron transmission housing is the early T10 used until 1966. Cast aluminium units are Super-T10 models, introduced in 1966. An extensive listing of vehicles using the T10 transmission is found on Drivetrain.com.