A turbodrill is disclosed which is connected to a string of drill pipe as a rotating shaft for driving a drill bit which may be a rotary bit or a high speed solid head diamond bit. The turbine section of the turbodrill has rotor and stator blades which are cresent shaped in cross section and are operated by drilling mud flowing therethrough to rotate the shaft. The shaft is provided with radial bearings which carry radial loads and thrust bearings which carry vertical or longitudinal loads. The thrust bearings, which carry the entire thrust load, consist of a pair of annular bearing plates each of which supports a plurality of friction bearing members, highly resistant to wear by the drilling mud flowing through the drill, consisting of cylindrical studs having flat faces with flat disc-shaped diamond bearing members supported thereon. There are preferably one more of the diamond bearing members on one of the annular bearing plates than on the other. This bearing arrangement can be used with sealed or unsealed constructions, since the bearings are lubricated by the flow of mud therethrough. The diamond bearings may be used with other types of downhole motor driven drills such as drills driven by positive displacement motors, and for other applications.