#Turbo 400 transmission serial number#

Additional Serial Number Info of the Turbo 350 and Turbo 400 Turbo 400 transmissions were partial VIN stamped either above the pan rail on the driver’s side (very difficult to see with the exhaust system installed) or on the driver’s side of the bell housing as indicated in the picture. The Turbo 475 was an extra-heavy-duty version and was found in larger trucks from 1971 on. It is identified easiest by its “375-THM” designation cast in the underside of the tail housing. The Turbo 375 was a version of the transmission used from 1972 through 1976, in small displacement cars. There are two significant variations of the Turbo 400. The 'kick down' switch locations for the Turbo 400 On ’72-’77 vehicles, the switch is located over the accelerator pedal. Generally, in ’68-’71 vehicles, the switch is located on the carburetor. Unlike the Turbo 350, instead of a “kick down” cable, it uses an electrical slide switch, which is controlled by the throttle linkage. The Turbo 400 is the largest of the GM auto transmissions, but still surprisingly compact in light of the immense power they can handle.Īnother quick way to identify a Turbo 400 is to look at the kick-down mechanism. It also uses the same vacuum modulator as the Turbo 350. The fluid pan shape is irregular, being likened to distorted Texas state borders. The 400 transmission has a main case of cast-aluminum alloy with a length of 24-3/8-inches long. The Turbo 400 has a very distinct fluid pan.