They are making changes to the 55cc, 75cc and 100cc fixed displacement motor and 55cc/75cc variable displacement motors. Right now it has an indented seat in the endcap. It gave it a more wearable area for the charge pressure relief valve poppet. Now it has been machined to sit right into the surface that it has been caste for. There will be new end cap part numbers for the updated design. With the new endcap, it is interchangeable with older endcaps and if you have an adjustable charge pressure relief valve parts. The older endcap will no longer be available for service parts. You can see the difference in the diagram below.
If you need further questions answer about this unit, call us at 662-871-8403
tupelohydraulics@gmail.com