On the worm shaft end play, this is controlled by steel balls in each bearing block. I have never seen them missing or with wear on them, but you might check. I think the important thing is that end play does not allow the worm wheels on the axles to get in to an area on the worm shaft where the worm is not fully cut.
I have seen bearing blocks that had visible flat spots worn into those steel balls. Unfortunately, I do not know of any way to remove / replace the balls. I don't even think they can be turned.
I guess the question is whether they are worn enough for the end of the shaft (the part not cut down) to rub against the face of the bearing block.
If anybody has a technique to replace those balls, I'd like to read about it.
If the end of the shaft was rubbing on the face of the bearing block, I think I'd try to find replacements, or perhaps put a thin nylon washer between the shaft end and the bearing block.
Another suggestion: Check whether your side rods binding in reverse.
I think it is possible for them to be OK going forward, but binding backwards due to slop in the drive train.
Factory spec on the brush: .4687 inches, including stepped portion
Factory spec on the brush spring: approx 1.000 inch.
