零件： 136-8869 vibratory piston motor for Caterpillar soil compactors, listed by Caterpillar as a Vibratory Piston Motor. Cross-references 0R-7784 and Bosch Rexroth R986110004.

What it drives: the eccentric shaft in the drum that generates compaction force. It is not a cooling fan motor, and it is listed in a compaction category for that reason.

Cat published dimensions: length 10.78 in, height 7.92 in, ductile iron construction.