An axle driving apparatus includes a first housing having a plurality of cooling fins, an axle rotatably mounted in the first housing, a hydraulic stepless speed change assembly disposed within the first housing. The axle driving apparatus also includes a second housing having a plurality of cooling fins, an axle rotatably mounted in the second housing, a hydraulic stepless speed change assembly disposed within the second housing. A connecting means, such as a bar and/or plate connects the first and second housings. The plurality of cooling fins on the first housing has a different configuration that the plurality of cooling fins on the second housing.