The spring PN for the fork is 16015, still readily available and all over eBay.
Fun fact - that PN is the original PN for that particular spring, going back to the first belt drive transmission in 1947. It is one of the very few items starting with 16xxx that remained through the last of the belt drives in the late 80's.
There was a brief period from 1959 thru 1964 where Whirlpool omitted the 16015 spring, in favor of the agitator shaft seal spring, 92815, and a revised fork that no longer interfaced with the lower section of the gear case. The updated agitator shaft spring was intended to replace the tension needed to hold the gear securely in place, but thankfully Whirlpool went back to the full length fork and the original 16015 spring paired with the new agitator shaft seal/spring assembly with the heavy duty gear case revisions in '64.
Ben
