Abstract: A well fluid pump assembly includes a rotary pump having a rotatable pump shaft. A motor is cooperatively engaged with the pump shaft for rotating the pump shaft. An upthrust module has an upthrust module housing having a lower end secured by a threaded engagement to an upper end of the pump. An upthrust module shaft is rotatably mounted in the housing and has a lower end in engagement with an upper end of the pump shaft for transferring upthrust on the pump shaft to the upthrust module shaft. An upthrust base is stationarily mounted in the housing. An upthrust runner is mounted to the upthrust module shaft for rotation therewith and located below the upthrust base. The upthrust runner engages the upthrust base to transfer to the housing upthrust applied to the upthrust module shaft from the pump shaft.