Lull 644b hydraulic pump failure

[rmllarue91]

Hi hef looking for some insight. Rear pump section keeps cracking two different pumps appears to be over pressure problem. Inspected relief valve and lowered pressure slowly turned it up until pressure was at 2250 everything worked fine set other relief for front section machine opperated normal . Drove machine 50 feet and pump blew out same extact spot as old one. I can make one pump of the two the housing is the same for front and back g2020 but any ideas what to look for. Plugged return line from relief valve? but releif worked fine down below 1500 psi it would dump ? Didn't seem to have issue until I drove but was not watching gauge when driving thanks

 

[rmllarue91]

 

[rmllarue91]

Well didn't get back to machine yet this is a pic of same model as one i'm working on. According to this machine and hydraulic schematic they have front and rear section hoses backwards. And front section is bigger than back best I can tell fronts are 13 gallons a minute and rear 9 gallons so possibly releif valve can't flow the additional 4 gallons a minute. Working on uploading hyd. Schematic

 

[tractormech]

Is it control manifold or mid inlet hydraulics? the compensator valve in the control block will make it do that with control manifold. Is the steering hard? that's usually a clue also.