I have wheeled excavator Case IH Poclain 888BP 1994 model. There was a problem with switching to high speed, before it turned on from the first time, then from the tenth, now it stopped altogether. Although when high speed was turned on, the excavator drove normally, but it was difficult to turn on. This is a problem with the solenoid valves that switch the hydraulics, and the question is where they are located and what they are controlled by and can something interfere with the switching?