hello all to whom reads, been fighting this dozer for awhile now and i could really use some advice. first inital symtom/problem - dozer was grading steep incline (jump face on dirtbike track) as dozer was climbing the hill it lost all pressure and free wheeled backwards down the hill till it got to flat ground and stopped rolling. there was no external leaks, engine was running fine, working equiptment still functioned normally but there was no drive and no pressure to the powertrain system. drive train and all mechanically linakge was still connected. hooked pressure gauges up to testing ports for power train control system found minimal pressure there way below specification. tested pressure out of pump and that was also below specification. first thing we had repaired was our hydraulic tandum pump. powertrain side of pump tested bad and working equiptment pump tested okay. we had pump fully rebuilt anyway, re installed pump and re checked pressures. still pressures were below specification and we were not getting the pressure to drive the machine. next was the transmission modulation/pressure valve removed and inspected then rebuilt the unit and reinstalled same symtoms low pressure not enough to move machine. we started going through the entire powertrain system and rebuilt and resealed every valve on the transmission (prioty valve, shift control valve, all brake and clutch valves, steering ppc valve and replaced any cracked or damaged hydraulic lines) we also removed the transmission and gone through and found foraward clutch assembly was burnt up so we replaced all clutches and piston ring seals for each pack and rebuilt and resealed transmission. while we had everything out before moving onto installation we had a look in steering case and found worn out clutch and brake steering pads so we replaced those as well. as well as making sure trasnmission oil cooler was clear and cleaned of any sludge after doing all this work and reinstalling and adjusting of all components and mechanical linkages as neccessary the machine is now moving and functioning but the pressure is still below specification and the fluid is aerated and the pump hums like its cavitating. causing heat at powertrain pump and filter. new fluid. new hose on suction side and triple checked suction screen + seals multiple times. when running the pump outlet line feels like its pulsating and my pressure gauge needle bounces. all my transmission vents are clear and venting correctly. my vaccum pressure should not be between -3 to -5 psi, i have -5 psi vacucum on suction side of pump currently. i need advice on where to go with this, any opinons is apprectiated!
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