This question comes up fairly often so I’m repeating a previous post for the newer folks. Also, the T-84 was used in the Studebaker Weasel.
The T-84 was not just used in the WW2 jeep. The jeep used the T-84J. Below are listed several (but not all) of the various vehicles that used a T-84. I didn’t bother to list them but there was at least one car, a Studebaker, that used a T-84 after the war.
(Information extracted from The Hollander.)
T-84A-1, 1A and T84B-1A
Continental Late ‘32-33 Flyer
Graham 36 80 Crusader
Continental ‘32 Beacon, Early Flyer
Mack ‘37-40 2M4A
Reo Truck ‘36-39 4-75, 3/4 ton
Willys ‘38-39 Pass.
Willys ‘39 Overland
Stude ‘39-40 Champion (over drive)
Nash ‘41-42 40
Am Bantam (Jeep) 40 BRC 1/4T 4×4
Willys 41-45 Army 1/4T
Ford Jeep ‘42-45 GPW 1/4 T 4×4
The T-84 gets a rap for being a bad and weak transmission. You have to wonder why it was used in some many cars (and trucks!) for so long a period of time, if better transmission were available.
If you need to work on a T-84, consider buying a copy of Trouble Shooting and Rebuilding the T-84J.