I rebuilt mine on my 1942 2-1/2T firetruck and it was basically just like the one I have in my newer (early) '47. it is a lever type on left of tranny and linkaged to rear at a relay lever by rods, and again to the back and pulled another linkage that just actuated the secondary brake pads via cable and spring. . So if this sounds like yours, check all relay connections starting from frame rail next to gear box and follow back and continue checking for movement. I had to fully remove my lever assembly and rebuild sepperately for smooth movement before I put it back in. Even rebuilt, it takes a lot to hold one of these big fore trucks or simular when loaded. I would hold foot brake in hard while pulling on hand brake to make sure it held.