The 9n9600-A&B were Donaldson air cleaners with the non-removable tops.These were used prior to serial number 5678.The 9n9600-C-1 was also Donaldson with removable top.The diff between the A&B was that the "A" had only one intake hole and the "B" had two intake holes in the non-removable top cover.Both had flat bottom cups and both used the 9n18215-A air intake tubes,due to the angle of the outlet pipe on the air cleaner. There was a vacuum port located on the lower back side of the 9N18215 "B" tube.The 9n9600 C-1[Donaldson] and the 9n9600 C-2 [United] had the screened removable top.The 9n9600 C-1 [Donaldson] used the flat bottom cup and the 9n9600 C-2 [United] used the round bottom cup. and the angle on the air cleaner outlet pipe was changed to use the 9n18215 B&C air tube.The "C" tube was then used thru 1952 8n tractors.Others may have more info than what I have,so like like all other 9n info,this info could change. don b

Thats interesting stuff. My early 40 had the B tube , never knew what that fitting was for on the back side.

Doug

Good to see you posting again, Don. I am just now printing off your post and this weekend I intend to go over the collection and see what variations I have on my collection of '39's and '40's. The oldest '39 that I own is 9N2158, the newest '39 is 77?? (I forget). I also have a fairly early '40 and a mid year '40. I do recall that I passed up a chance to buy 9N9??? (I forget again - senior moments here) about a year ago and it had the round bottom screen top air cleaner.

Bob

Good info! I've never seen a 9N9600-A or B. Now I'll know what it is if I ever run across one. This should be moved to the history page.

Jim, Here's a picture of one.