In Reply to: Donaldson Air Cleaner Cup? posted by Del Huebner on June 10, 2017 at 13:48:49:
Yes, that is the Donaldson cup. The air cleaners were supplied by Donaldson and United and cups were different, but there is a note, more later. The United Service cup is round-bottomed. Now, in the March, 1940 MPC, the very first 9N parts catalog, on page 33 the section on AIR CLEANER lists 9N-9600-C1* as the Donaldson and 9N-9600-C2* as the United. The star symbol suffixes noted mean there's more info so flipping to the end, on page 47, lower right hand of page shows the star symbol and its use. The note says, "Used on all tractors after (s/n) 5677 EXCEPT those listed below. Your 9N-3662 would have the Donaldson but the note also means if air cleaner needed to be replaced, the United would be the one to order and you would swap out. Also the pipes are different too. According to the note, the cups and clamps can be interchanged. I never knew this but don't have a United air cleaner to test with my 9N-653I model with a Donaldson. Amazing how we can learn new stuff all the time, eh? BTW, do you have the correct Donaldson decals for yours?