John Deere Mikanix

317/320 Skid Steer doesn't drive straight

Complaint:
The wheels on one side of the machine will not come back up to full speed after slowing them down to make a steering adjustment. This occurs most frequently when traveling down hill, but has also happened on level ground.
Problem or Situation:
John Deere has found that this was a typical situation on a 317 and 320 and is caused by the hot oil shuttle (flushing valve) moving to the reverse direction when slowing the wheels and sticking in that position. This allows some of the drive pressure oil to leak past the shuttle, reducing the forward wheel speed until the flushing valve shifts back to the forward direction.Solution:
The former flushing valve used 6-bar springs.  It has been determined that this pressure is too low.  A new 10-bar flushing valve assembly is now available to correct this problem.  The 10-bar flushing valve assemblies were being installed in all production motors as a running change.  Serial number breaks for this change were captured in the appropriate parts catalogs.
The part number for the 10-bar flushing valve assembly is T223651.  This shuttle valve replaces the 6-bar shuttle valve assembly T208293.
THIS IS VERY IMPORTANT:  The flushing valves must be matched side-to-side.  You cannot have a 6-bar flushing valve on one side and a 10-bar valve on the other side.  After the 10-bar shuttle valve is placed in production, all service part drive motors will be equipped with the 10-bar shuttle valve.  You will not be able to purchase a 6-bar shuttle valve motor.  Therefore, if you are replacing a drive motor that was built before the 10-bar shuttle valve was introduced, the shuttle valve in the remaining motor must be replaced with T223651 to ensure that both motors are equipped with 10-bar shuttle valves.
The flushing valve kits will be provided by your dealership but you have to order them.  If Installation Instructions are not included with the kits, use the procedure below to replace the flushing valve.
1.  Remove the plug (151Z0366), both springs (663X6251), spool (151Z0368), and lower guide (151Z0367) from the end plate of the motor. 
NOTE:  Be sure that the lower guide (151Z0367) is removed from the end plate.  Failure to remove the lower guide will prevent the spool from properly seating in the end plate and will cause plug leakage.
2.  Discard all of the parts removed in step 1.
3.  Install the springs (663X6253), plunger (151Z0424), and plug (151Z0422) into the end plate of the motor.  Torque the plug to 30 Nm (22 ft. lbs).
4. Repeat steps 1-3 for the remaining motor (if both motors are being worked).
5. Start the machine and check for leaks.

Courtesy of John Deere DTAC Solutions