A vibratory roller or soil compactor densifies material with an eccentric shaft driven by a dedicated hydraulic piston motor, not by the engine. That motor is the part that decides amplitude and frequency, and it runs in the dirtiest, hottest oil on the machine because the drum bearing seals eventually let fines through.This section covers replacement vibratory piston motors for Caterpillar CP and CS compactors, including the 136-8869 used across the CP-54, CP-56, CS-54, CS-56, CS-531, CS-533 and CS-563 families. These are compaction motors, not cooling fan motors, and we list them separately so a buyer searching for a fan part is never sent here. Send the number cast on your motor and the machine serial prefix so we can confirm the correct shaft, flange and displacement before shipping.