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A hydraulic motor assembly having a motor and gear reduction set mounted in a housing having a motor sump and a gear sump. The housing may be formed of separate components, including the external surface of the ring gear and the hydraulic motor port block. A case drain comprising multiple passages

A hydraulic motor assembly having a motor and gear reduction set mounted in a housing having a motor sump and a gear sump. The housing may be formed of separate components, including the external surface of the ring gear and the hydraulic motor port block. A case drain comprising multiple passages permits hydraulic fluid to pass from both the motor sump and from the gear sump to an external sump.

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We claim: 1. A hydraulic motor assembly having a casing, the motor assembly comprising: a motor housing forming an internal motor sump and having an external surface forming at least part of the casing; a case drain formed on the external surface of the motor housing; a hydraulic motor disposed in

We claim: 1. A hydraulic motor assembly having a casing, the motor assembly comprising: a motor housing forming an internal motor sump and having an external surface forming at least part of the casing; a case drain formed on the external surface of the motor housing; a hydraulic motor disposed in the motor sump and driving a motor shaft; a gear train located in a gear sump and engaged to the motor shaft; and a port block engaged to the motor housing, the port block comprising a motor running surface, hydraulic porting in communication with the hydraulic motor and a first drain passage in communication between the gear sump and the motor housing case drain to permit hydraulic fluid to be drained from the gear sump to an external sump. 2. A hydraulic motor assembly as set forth in claim 1, further comprising a ring gear having an external surface forming a part of the external casing and an internal surface having a gear surface formed thereon, wherein at least part of the gear train runs on the gear surface and the internal surface forms at least part of the gear sump. 3. A hydraulic motor assembly as set forth in claim 2, further comprising an axle housing having an output axle disposed therein, and the output axle is engaged to and driven by the gear train. 4. A hydraulic motor assembly as set forth in claim 2, wherein the ring gear is sandwiched between the axle housing and the port block. 5. A hydraulic motor assembly as set forth in claim 4, wherein the gear train comprises a first planetary gear reduction set driven by the motor shaft and running on the ring gear. 6. A hydraulic motor assembly as set forth in claim 5, further comprising a second planetary gear reduction set driven by the first planetary gear reduction set, and the second planetary gear reduction set engages the ring gear. 7. A hydraulic motor assembly as set forth in claim 1, wherein the hydraulic motor comprises an axial piston motor having pistons which move in a direction parallel to the motor shaft. 8. A hydraulic motor assembly as set forth in claim 1, further comprising a second drain passage formed in the port block to permit fluid communication between the motor sump and the gear sump. 9. A hydraulic motor assembly as set forth in claim 8, wherein the first drain passage and the second drain passage are in generally opposite sides of the port block. 10. A hydraulic motor assembly having an external casing and connected to an external sump, the motor assembly comprising: a motor housing having an internal motor sump; a hydraulic motor disposed in the motor sump and driving a motor shaft; a gear sump formed in the assembly and having a gear train located therein, wherein the gear train is drivingly engaged to the motor shaft; an axle housing having an axle mounted therein, wherein the axle is drivingly engaged to the gear train; a port block mounted between the motor housing and the axle housing; and a case drain comprising a first drain passage formed in the motor housing and in communication with an external sump and a second drain passage, wherein the second drain passage permits hydraulic fluid to pass from the gear sump to the first drain passage. 11. A hydraulic motor assembly as set forth in claim 10, wherein the gear train further comprises a ring gear having an external surface forming a part of the external casing and an internal surface having a gear surface formed thereon, wherein the ring gear forms at least part of the gear sump. 12. A hydraulic motor assembly as set forth in claim 11, wherein at least part of the gear train runs on the gear surface. 13. A hydraulic motor assembly as set forth in claim 12, wherein the gear train comprises a first planetary gear reduction set driven by the motor shaft. 14. A hydraulic motor assembly as set forth in claim 13, wherein the gear train further comprises a second planetary gear reduction set driven by the first planetary gear reduction set. 15. A hydraulic motor assembly as set forth in claim 14, where the first and second planetary gear reduction sets are both running on the gear surface of the ring gear. 16. A hydraulic motor assembly as set forth in claim 10, further comprising a third drain passage formed in the port block to permit fluid communication between the motor sump and the gear sump. 17. A hydraulic motor assembly as set forth in claim 16, wherein the second drain passage and the third drain passage are located in generally opposite sides of the port block. 18. A hydraulic motor assembly as set forth in claim 16, wherein the first drain passage and the second drain passage are generally collinear at the interface between the port block and the motor housing and extend in a direction generally parallel to the motor shaft. 19. A hydraulic motor assembly as set forth in claim 10, further comprising a third drain passage formed in the port block to permit fluid communication between the motor sump and the gear sump, and wherein the port block is adjacent the motor housing and the ring gear is adjacent the axle housing. 20. A hydraulic motor assembly as set forth in claim 19, wherein the second drain passage and the third drain passage are located in generally opposite sides of the port block. 21. A hydraulic motor assembly as set forth in claim 11, wherein the port block is adjacent the motor housing and the ring gear is adjacent the axle housing. 22. A hydraulic motor assembly having an external casing and connected to an external sump, the motor assembly comprising: a motor housing member and an axle housing member; an internal motor sump formed in the motor housing member; a first drain passage formed in the motor housing member and in communication with the internal motor sump and an external sump; a hydraulic motor disposed in the motor sump and driving a motor shaft; a gear train located in a gear sump and drivingly engaged to the motor shaft; an axle mounted in the axle housing member and drivingly engaged to the gear train; and a second drain passage to permit hydraulic fluid to pass from the gear sump to the first drain passage.