did someone make axles or machine them down or worn down some how ? maybe measure OD if you can with calipers or micrometers
just to be safe you never know what a previous owner did ??
also agree with Steve, check and see if there are numbers on the seals. odd they would be loose as it seems the inner portion of the shaft is a larger OD then the outer !!
looking at TFS website did you buy the KIT
they list 2 kits one being AF-506SM which is kit for small axle ?? Small axle diameter at hub 1.275 with 3/4" nut, has it has 2 INNER seals AF-506 then 2 OUTER seals RW-41 shaft measures 1.033" plus two outer seal retainer gaskets (G-5547)
they also make the Large Axle KIT AF-506LG Large axle diameter at hub is 1.375, with 13/16" nut, it has 2 INNER seals AF-506 then 2 OUTER seals RW-41 shaft measures 1.127" plus two outer seal retainer gaskets (G-5547)
you can also order JUST the seals and gaskets individually if needed. looks like either axle uses the same inner seals and gaskets but different outer seals due to diametrical difference.