CARRIER 3K4170 - Caterpillar

--------------- END SUPPLEMENT ---------------Description of Change: A pressure relief fitting has been added to the front hub (cover) of the 3N7846 Fan Drive Groups for the above model engines. The new fitting will let air out of the fan hub during lubrication, so the grease can flow through the front bearing. Formerly, the front of the hub was sealed, and it was possible for air pressure to keep grease out of the front bearing.Adaptable To: All earlier engines. One 4B4550 Fitting (Pressure Relief) is added to the 3N7846 Fan Drive Group. The fitting is installed in the center of the 1N5936 Fan Hub, which is the front cover for the 7F9949 Hub. The part number of the 1N5936 Fan Hub did not change, but later hubs have a hole for the fitting. For conversion of earlier engines, a hole can be added to the existing 1N5936 Fan Hub, and the 4B4550 Fitting installed. Remove the hub, drill an 8.74 mm (.344") diameter hole in the center of the hub, and tap 1/8-27 NPT.
Thoroughly clean the hub, then install the hub and the fitting. Grease can now be added to the fan hub until it comes out through the new pressure relief fitting. This will make sure the grease has come through the front bearing, so it has positive lubrication. Remove any grease that comes through the fitting so it will not get on the fan blades or belts, or be thrown into the radiator core if the engine has a blower fan.