The WW2 jeep like any vehicle is made up of thousands of parts. The parts are not all made by the automobile manufacturer. Other companies produce the parts that are used in the vehicle. This was true with the Ford and the Willys WW2 jeep. One relatively small but impart part was the two Bristol screws used in the T-84 jeep transmission.
- According to Wikipedia: The Bristol screw drive is a spline with four or six splines, which are not necessarily tamper resistant. The grooves in the wrench are cut by a square-cornered broach, giving a slight undercut to the outer corners of the driver. The main advantage to this drive system is that almost all of the turning force is applied at right angles to the fastener spline face, which reduces the possibility of stripping the fastener. For this reason Bristol screw drives are often used in softer, non-ferrous metals. Compared to an Allen drive, Bristol drives are less likely to strip for the same amount of torque; however the Bristol drive is not much more strip resistant than a Torx drive. It was created by the Bristol Wrench Company.
The T-84J transmission is used in the WW2 jeep. It is a very basic transmission and relatively easy to work on. You only need a few tools and either the TM 9-1803B Power Train, Body, and Frame for Willys Overland Model MB and Ford Model GPW 1/4 Ton 4×4 Technical Manual or my own book, Trouble Shooting and Rebuilding the T-84J Transmission, that goes into much more detail.