This is the best information you will find on truck steering boxes, it is for a newer box, but they all adjust the same way.
https://www.flickr.com/photos/advance-design_parts_co/sets/72157632210242370/The '41 gear box is designed just like the '42 - '46 box with roller balls and a cage, very much like the ones in the link above. The '41 differs slightly from '42-'46 with different size roller balls. This makes the cage and worm gear different size also. I say this, because most assume the '41-'46 are the same and buying parts can get you in trouble.
Good thing about these boxes is the 1/2 ton to 5 ton all use the same basic box with the difference being the steering shaft length. So if you need parts, don't limit the search to 3/4 ton only.
If you take some time and shop e-bay, you can find NOS parts. I rebuilt my '41 box with all NOS parts. Jim Carters Truck parts is now selling new worm shaft and cage for these, so thats an option as well. The cage nut and sector are the two wear items. The lower ball bearing on the worm shaft should also be checked closely, this is where water collects over time.
