TRANSMISSION LUBRICATION 1P4790 - Caterpillar

3400 Series EnginesDescription of Change: Wider, taper-type connecting rods are now used in the the piston groups for all 3400 Series Engines. The wider connecting rods have a piston pin bearing with more area and can operate under higher cylinder pressure than the former rods. The new parts give longer service life.Adaptable To: The new, wider, taper-type connecting rods are a direct replacement for the former, wider, straight connecting rods as shown in the chart. However, pistons with narrow, taper-type connecting rods are still serviced with the narrow, taper-type rods. The location of the part number on the rod can be found on top of the connecting rod eye. Positive identification of the connecting rods by this number will prevent the narrow and wide taper-type rods from being mixed during installation. No changes have been made to the 3408 P.C. Engines, which have a 7N3517 Rod and Piston Group. The new taper-type connecting rod is not adaptable to the 3408 P.C. Engine pistons because of possible interference with the piston skirt.