Gear pump rebuild questions

[IH3444]

Gear Pump - Working Principle, What Is Backlash?

As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to

mechanicalportal.com

The gear backlash on my 1971 IH3444 Industrial TLB were pass 0.020 of an inch, so I had to also replace the gears. $150 for two gears back in 1987. After warm up oil can be squeezed backwards through too much clearance on gears backlash. I did all mentioned here also. Flatten plates, re-shimmed pressure relief. The clearance around the housing that supported the gears was acceptable. Had to purchase gears from IH dealer. No one else had them.
Push gears together clean and dry in direction of pumping. Take a feeler gauge and measure clearance between gears on back side. I think 0.008 was minimal acceptable, mine were shot at 0.020.

 

[LD1]

Most people dont rebuild pumps anymore because the machining cost and labor dont make it very cost effective. And most of the pumps people are dealing with are <$500...so they just replace.

However you are in a unique situation with the time and ability to do the job and not pay a shop ~$100/hr to do said work.

I would try and contact the manufacture....or even a case industrial dealer and see if they can dust off an old book somewhere because I am sure there is a spec.

I do agree with oldnslo that if practical, disassemble and find a spot that isnt worn and measure it and the gear and use that as a baseline.

Two clearances to worry about, which is gear to case as well as gear to end plate.

My gut says 0.002" is too tight for a pump. I was thinking more like 0.005" or a tad more. 0.002 is knocking on engine main bearing clearance tolerances.

Curious.....does RPM have an effect on your pressures? Usually a big symptom of a worn pump is inability to make pressure at lower RPM.

Let us know what you decide to do or what you find when you take it apart