Patent ID: 8668612

Claim:
A lubrication structure of a differential gear unit that i) includes a differential case that houses a differential gear unit therein and is rotatably supported via a bearing by a hollow supporting portion of a case of a power transmitting apparatus, and a ring gear that is fixed by a bolt to the differential case, and that ii) lubricates the bearing with hydraulic fluid, comprising: a through-hole that is provided in an upper portion of the hollow supporting portion and extends in a vertical direction; and a guide rib that axially extends over a certain area with respect to a rotation path of a head of the bolt when the ring gear rotates, and that protrudes out from the case toward the head of the bolt such that contact between the guide rib and the bolt head maintains a clamping force of the bolt, wherein the guide rib has a guide portion positioned above the through-hole with respect to the rotation path of the head of the bolt for guiding lubricant to the through hole.