Howdy First post. Been reading any thread I can find of intermittent drive on one side, one direction only. Reverse on left side is quirky. Sometimes it will not start driving until the stick is pulled back much farther than it should have to be, for initial drive, and then it jerks in hard (both wheels move in unison, don't think it is chain problem). Sometimes it stops working at all, again only left side reverse (usually under lower throttle settings). When it does stop working if I push left stick full forward quickly, then back to reverse quickly, reverse starts working again. Sometimes it seems to work normal. Have full power and normal drive in fwd left, fwd and rev on right. Checked linkages and centering plate mechanisms, all seem OK. No leaks that I can see, hydraulic resrv. is full, not overheating. Many threads talk of checking/swapping around replenishing valves. I found a thread with a serial number (mine is 511351589) that was higher than mine and the poster was instructed the replenishing valves were on the front and back (not top and bottom). Just curious if this applies to me also? If they are top/bottom, assume you have to pull the whole assembly to get to bottom one's?? Found another thread that claims there are shuttle valves inside the hydrostatic pumps. Is this yet another control valve, or is it just another name/description for the replenishing valve? Also, is there any chance the charge relief valve (valves??) could cause a problem like this? I assume there is only one and that it would affect all drive (or none) if it was hanging up? Thanks in advance
Help Support SkidSteer Forum:
The shuttle valve is in the drive motor, not the pump.
If you swap drive motors, see if the problem moves. If it does, the motor is to blame, if not it is the pump. That is where i would start before moving on to more detailed things.
The relief valves for the motors are behind allen headed bolts, or part of them to be exact. Naturally two are on the top, two are on the bottom. They are under the centering plate.
If you swap drive motors, see if the problem moves. If it does, the motor is to blame, if not it is the pump. That is where i would start before moving on to more detailed things.
The relief valves for the motors are behind allen headed bolts, or part of them to be exact. Naturally two are on the top, two are on the bottom. They are under the centering plate.
OK, thanks. What do the shuttle valves do, redirect high pressure to either side of the motor to reverse flow (direction)?
To be honest, I'm not exactly sure why it is needed. From what i understand, to reverse direction of the motor, the oil flow reverses from the pump. This means that each change the high pressure side of the motor changes. The shuttle valve as i understand it allows some of the oil from the lower pressure side of the motor to flow back to the tank so fresh cooler oil is drawn back into the system to assist in cooling. You don't want the high pressure side trying to escape through the case drain port when it is meant to be making the motor work.
As i said, this is how i understood how it worked, if it's different, hopefully someone that knows better will give us a lesson
After further digging, it appears the shuttle valve and relief valve (in the motor) meter fluid back to the cooler so the motor does not overheat. I don't see how the shuttle valve in the motor could cause intermitant problems with drive in only one diection. See page 5 here. http://www.eaton.com/ecm/idcplg?IdcService=GET_FILE&allowInterrupt=1&RevisionSelectionMethod=LatestReleased&Rendition=Primary&dDocName=DEV_216715 Shuttle valve is in center (symetrically) on motor and does not appear to operate differently for either direction the motor is running. So In my case, where fwd on that site operates flawlessly, I have to think it is in the hydrostastic pump/replenish valves. Thing that has me confused is I have read a ton on here and I seem to recall some suggestions that drive loss in only one direction (one side) did turn out to be something wrong with the motor in some cases. Anyway, when I get time, will swap motors and see what happens. If the problem does move with the motor, I would at that point be completely baffled about what I think I know about the motor (and it's shuttle valve). Do you know of a internal schematic of the hydrostatic pump/replenishing valves similar to the motor PDF I listed above?To be honest, I'm not exactly sure why it is needed. From what i understand, to reverse direction of the motor, the oil flow reverses from the pump. This means that each change the high pressure side of the motor changes. The shuttle valve as i understand it allows some of the oil from the lower pressure side of the motor to flow back to the tank so fresh cooler oil is drawn back into the system to assist in cooling. You don't want the high pressure side trying to escape through the case drain port when it is meant to be making the motor work.
As i said, this is how i understood how it worked, if it's different, hopefully someone that knows better will give us a lesson
It is always possible it's the valves in the pump, but go with the motor first, it's easier.
