I have a 1986 dresser 510 loader, great little machine. have had no issues since in my possession until now. Was shifting fine from forward to reverse day before, just moving around chips. Now wont engage in either. tries to move forward or reverse slightly, almost as if the tranny is deactivated by the switch on the second brake pedal but that system was deleted by previous owner. look for a direction to go to trouble shoot. dont think its the torque converter, had no indication of slip or anything the day before. PLease advise Thanks Lee
Typical power shift system oil flow is 1. supply oil to charge pump. 2. Charge pump to trans clutch (There is usually one speed clutch activated at any time)through clutch pressure regulator valve. 3. once required clutch pressure is achieved regulator valve shifts and sends oil to the converter, then system is set to go. If the charge pump cannot achieve clutch pressure no oil will get to the converter. If the clutch pressure regulator valve is stuck open oil will go directly to the converter which will try to make the machine move once fwd or rev is selected there won't be enough pressure at the clutches to move the machine other then friction between the clutch plates and the oil between them may give the feeling that the machine is trying to move. That's the way it is supposed to work, However if the trans oil level is way low or the charge pump has failed, or the converter drive from the engine to the converter has failed, or the charge pump drive is broken or stripped. first check would be oil level, next would be check clutch pressure, if it is normal or near normal, regulator valve may not have shifted or partially shifted so the converter can't get a full charge of oil, if it is low or way low could be there is a problem with the supply to the charge pump.
Wow, thank you for your post!!!! I checked the oil sight glasses and both are full and clean. The machine has no leaks, amazingly dry for the age. Its reacting like the clutch pressure regulator valve is stuck open, from your description. I need to locate that valve or the sensor that activates it. I was thinking electrical, the machine has always been reliable but had to chase the mice out, machine has been sitting more than usual but never longer than 2-3 weeks. The wiring was a bit of a mess from the previous owner but ive fixed most of it. There are a few sensors on the side of the transmission control housing. i know the one to the rear and lower is the solenoid that stops the drive to the drive train with the left brake pedal but it metered out 0 voltage and would have been 24-27 volts if it was being activated by a short and the previous owner deleted the activation switch on the left pedal for some reason. My 520 still has it and it works perfectly. Ill keep at it and thanks for your input. i have the manuals for my 520 and have be referencing them.
latest update, still working on it So the oil is not low and when i start it up and idle up the oil in the windows look as if it is getting foam or cavitation bubbles in it. Can you direct me to the clutch pressure regulator or how to check the pressures?
any advise out there?
Fixed! So it ended up being the pickup screen in the trans pan.. cleaned and resealed and presto, changed the hydraulic filter as well.