caterpillar 515 diff lock

4lr578 winch machine diff locks haven't worked in awhile. A few wiring issues and got the solenoids working. Could'nt build pressure on front or back circuit. oil levels were right 50 weight oil about 30 degree air temp. Rear circuit filter bypass stuck. Front circuit front section of pump inoperable housing scored from front rear failure in the past. Install new pump and filter housing pressure looks good rear pressure hose has slight vibration but thought might of been acceptable. Diff locks work for short time and quit. No flow out off pump. Disassembled new pump back section welded gears to shaft and ground housing down. Looks like heat damage and when back section locked up broke and front section broke a gear. So built a used pump from the two. Installed and back section pressure hose between filter and pump vibrates pretty bad. Got new suction hose and seems a little better but not enough good oil flow from suction fitting at bottom of rear. Both front and back section of pump seem to be getting warm really fast. And fluid at filter housing seems airated. Both pressures stay at 375psi right at pump out let and on lines going in to the rears. Any ideas welcome

caterpillar 515 diff lock