Just for example, my JD 210C is somewhat of a less common model machine, yet many of the parts interchange with other deere machines, transaxle is same as 310 and early 410, axle housings I was able to get from a 60s vintage ag tractor. So even tho model numbers may change often times the basic machines are the same or the parts to make the change are used on other machines too. Despite all this I had a great deal of trouble finding used axle housings for my machine since while they rarely failed on a 210 model the larger 410 model destroyed them regularly thus eating up a lot of the salvage market supply