Need Info

That 9V serial number is mentioned in an old post as a #41 control. I think on a D4 it is 12.5 gpm and the relief is set pretty low, like 750 psi. There are some parts diagrams for other series #41s posted so you might find something useful there. The D2 turns at a little higher rpm, so the gpm is a little higher on both the #44 and the #41.

Do the cylinders retract to lower the doze or extend? If they retract, I could see the level of the oil in the reservoir rising by the volume of the cylinder rods, so if it was filled chock full, the oil displaced by the rods would overflow. If it only does it with the pump not turning it seems like it must have some trapped air in the system somewhere. I know some newer Caterpillar machines are designed with a pressure relief and a sealed cap so the hydraulic reservoir builds pressure as it heats up, presumably to lessen the chance of cavitation in the pump. Not sure on the old ones.

Does your oil seem to have air entrained in it?

There is also a 9W series of #44 controls if there could be a mistake reading the number stamping.

[quote="ccjersey"]That 9V serial number is mentioned in an old post as a #41 control. I think on a D4 it is 12.5 gpm and the relief is set pretty low, like 750 psi. There are some parts diagrams for other series #41s posted so you might find something useful there. The D2 turns at a little higher rpm, so the gpm is a little higher on both the #44 and the #41.

Do the cylinders retract to lower the doze or extend? If they retract, I could see the level of the oil in the reservoir rising by the volume of the cylinder rods, so if it was filled chock full, the oil displaced by the rods would overflow. If it only does it with the pump not turning it seems like it must have some trapped air in the system somewhere. I know some newer Caterpillar machines are designed with a pressure relief and a sealed cap so the hydraulic reservoir builds pressure as it heats up, presumably to lessen the chance of cavitation in the pump. Not sure on the old ones.

Does your oil seem to have air entrained in it?

There is also a 9W series of #44 controls if there could be a mistake reading the number stamping.[/quote]

The cylinders retract when lowered. There seems to be no bubbles or foaming of the oil. It doesn't dump oil if I engage the pump so that's what I do. I will research the #41 to see if I can find a cap. Thanks for the help

if in fact they are low pressure, older Rams , try rebuilding them. not many things are simpler or cheaper.
if necessary, clean up the bores with a universal cylinder hone.

take the seals and packing to any hydraulic shop, mine cost $50.00 per side. mine looked bad, but after new seals, still no leaks 1 year later.

[quote="TOGNOT"]if in fact they are low pressure, older Rams , try rebuilding them. not many things are simpler or cheaper.
if necessary, clean up the bores with a universal cylinder hone.

take the seals and packing to any hydraulic shop, mine cost $50.00 per side. mine looked bad, but after new seals, still no leaks 1 year later.[/quote]

I sanded out some pretty bad rust spots on two large old low pressure cylinders off a D7 and with no chrome left in large areas of the rods I got many hours of service out of them using them hard on a log splitter with no leaks to date. Modern seals obtained from my local hydraulic shop fitted in the end cap work very well.