During 1939-40 Door window breakage on truck cabs became a problem. As the cloth fabric in the door window channel became worn, the large and now loose fitting side windows were susceptible to cracking when the door was slammed. Complaints from dealers resulted in an improvement on 1941-46 doors. A one piece metal frame was placed around the edges of the top and sides of the glass and the breakage was greatly reduced. To make room for these new metal frames, the glass on the 1941-46 doors was now slightly smaller.
Therefore, the 1939-40 door glass and 1941-46 with metal frame will interchange in total in all 1939-46 doors. The smaller 1941-46 door glass can not be used without it’s frame or it will not seal into the cloth channel at the top of the window opening.