The post below on putting a hydraulic pump on a M and some answers brings up a question I would like to ask. Seems to be a lot of different answers as to when the increased strength camshaft gear 6760 DA started being used in farmalls. Does anyone know exactly when 6760 DA was first used in a production farmall. I think there should be a bulliten that IH sent out to dealers or parts depots anouncing the change of gears somewhere around if someone has some. I do have one anoucing the change to 6760 DB but haven't located one for change from 6760 D to 6760 DA. Any comments or help is welcome. From what information I have I think the change was made to the stronger gear from sometime in later 53 to later 54. Can't find proof that any M tractors came with gear 6760 DA.

Dave:
I'm assuming the DA gear was stronger than the D, and the DB gear was even stronger than the DA version?
When was the DB gear introduced?
mike

Mike this is what the bulletin S-7964 says.
Camshaft gear C 248 and C 264 engines. Camshaft gear # 6760 DA currently specified for production and/or service use in C-248 and C-264 engines is revised to provide a tighter and improved fit on the camshaft. Part # is advanced to DB to identify change. Reason to overcome field complaints of gear loosening on camshaft.
Effective F 400# 21314 Engine # 155941. Effect on service parts: Furnish new soon as available for farmall 400 400HC and international 400 tractors and when old stock is exhausted in all other applications. Note to prevent damage to camshaft while pressing on new tighter fit gear, support camshaft from rear face of front bearing journal. Sent to all district offices, transfers and parts depots. This is dated 10-12-1955, but I think the production tractor was assembled in july 55. DB went on to 450 tractors also
Mike hope someone has one of these bulletins for change from D to DA. Have thought about contacting the WHS to see if they could check or let a person look if in the area. Mike D is not as thick in hub as DA. Change in DA and DB covered above. Last print parts books and CIH site will only show updated parts if they fit earlier tractors, not when changes were made. My guess is SM tractors hydraulic system was easier on gear than 400 tractors and that lead to change above. I suspect IH didn't install the DA gear in tractors until after live hydraulic was offered. My opinion only though. Hard to say with a lot of gears changed out in last 50 or 60 years. I have torn very few of the engines down that the cam nut lock wasn't bent ( if used wasn't needed if cam was replaced with left hand thread type also production in some 450) more than once, indicating previous removal. Dave

Thanks, Dave. That is very interesting information.
mike