BOLT 4578758 - Caterpillar

In addition, some confusion exists as to the location of the front timing gears in different applications, such as adding attachments or changing the direction of rotation of an engine. Use the illustrations as a guide for correct location of the front timing gears.
The accessory drive gears and the auxiliary drive gears must always rotate in the same direction, regardless of the direction of rotation of the engine.Use Chart B for identification and application of gears shown in the illustration.
Illustration 1. Front timing gears, high speed, SAE Standard Rotation.
Illustration 2. Front timing gears, high speed, SAE Opposite Rotation.
Illustration 3. Front timing gears, slow speed, SAE Standard Rotation.
Illustration 4. Front timing gears, slow speed, SAE Opposite Rotation.