CYLINDER G 3K2370 - Caterpillar

Illustration 1. Location of identification is marked on front end of crankshaft.To find the top center of the crankshaft number one journal when the crankshaft is installed in the engine, it will be necessary to use a dial indicator to find the top dead center position of the number one piston. This will put the top dead center position of the crankshaft 30 degrees counterclockwise from the vertical centerline as shown in Illustration 1 and 30 degrees clockwise as shown in Illustration 2.
Illustration 2. Location of identification marks on rear end of crankshaft.The next two teeth counterclockwise (as seen from the front) have two punch marks along the length (top) of the teeth. These two teeth are used for alignment with the "R" mark on one tooth of the 4L3406 Idler Gear when the engine is changed to reverse rotation. There is only one marked tooth on the rear crankshaft gear. See Illustration 2. This tooth has four to six punch marks on the top. It has a location 30° counterclockwise (as seen from the rear) from the centerline of the last crankshaft journal. Since the teeth on the gear are 7.5° apart, one tooth will be in alignment with the center of a threaded hole in the crankshaft flange. The tooth with the four to six punch marks will be the fourth tooth.
This information permits a fast way to tell if the crankshaft is installed backwards, if the "FRT" mark was left off or put on the wrong end of the crankshaft. It does not tell if the teeth are marked correctly or in alignment when viewed with the damper or flywheel removed. It does permit a quick check to determine if the crankshaft is in backwards even if "FRT" isn't stamped on the crankshaft or is stamped on the wrong end. To check for correct tooth alignment of the gears, additional disassembly of the flywheel or front accessory housing is necessary.