Power train mechanism including a surrounding member

An automatic transmission comprising:

• at least one rotating member, said rotating member including a clutch drum and a shaft, said clutch drum having a frictional engagement element being lubricated and cooled by oil;
• oil supply passages that supply oil to said rotating member, said oil supply passages being disposed in said shaft;
• an oil reservoir provided below said rotating member in a radial direction of the rotating member;
• an outer circumferential surface surrounding member that surrounds an outer circumferential surface of the rotating member, a first side of said outer circumferential surface surrounding member faces said outer circumferential surface with a clearance therebetween to such a degree as to avoid contact with said outer circumferential surface during rotation of said outer circumferential surface of said rotating member;
• and
• an end surface surrounding member provided continuously to said outer circumferential surface surrounding member, said end surface surrounding member axially surrounding one end surface of said rotating member,
• wherein a side of said outer circumferential surface surrounding member axially opposite to said end surface surrounding member is an open end, and
• wherein a bottom portion of said end surface surrounding member and a second side of said outer circumferential surface surrounding member, opposite said first side of said outer circumferential surface surrounding member, define the oil reservoir, said outer circumferential surface surrounding member is located closer to said rotating member relative to the bottom portion of said end surface surrounding member, and the open end of said outer circumferential surface surrounding member is located between the bottom portion of said end surface surrounding member and said rotating member.