Here is a pic where you can see the glue. Really not a problem once they are glued.
It's a simply fix and requires much less effort than keeping your 511 diffs clean. 511 fan-boys like to point this out as one of the design flaws of the 502, but really it is not as much of a problem as the 511's have with the completely exposed diffs and required custom gear box covers etc. I.E. you can use a cheap and readily available commercial off-the-shelf part to solve the problem on the TRF 502X.
Sorry about the ripped boots. If we ever meet face-to-face I owe you $2.99. Wish I had remembered the glue detail.