History and Identification of the T-90
The T-90 was used by Jeep from '46-'71 and has a legendary reputation as a compact tranny (the case is only 9 inches long) capable of withstanding a lot of abuse behind V-8 power. It is an updated version of the T-84 used in WWII jeeps and has a synchronized Second and Third gear; First and Reverse are nonsynchronized spur gears. The tranny is best identified by a six-bolt top cover, the "T-90" cast in the iron case, and a prominent bulge on the driver side (these serve as the location for the actuators on column-shift models).
There were three main versions of the T-90; the T-90A1 was used behind L- and F-head four-cylinder engines from '46 to '62. The T-90C was used from '63 to '71 and uses an "A" case with a different input-gear length and tooth count. The T-90J was used from '52 to '65 behind six-cylinder truck engines and had a longer 11-inch input shaft with both column and top-shifting varieties.
It appears as though the transmission used in this article was original to the Jeep but had a later six-cylinder input shaft installed (a popular trick back in the day) as part of an ancient conversion to an early-bolt-pattern Ford 289. Though many parts are interchangeable among the three versions, there are differences. Bottom line: Even the newest T-90 is very old with a good chance that it's not original to the vehicle, so consult Novak's Web site for proper identification of your tranny before ordering your rebuild kit.