I was wondering if any one knew tha RPM or the front of the crank i am trying to find a hyd pump to mount i think that i want about 30 to 40 gpm but not sure. i will takw any input that i can get thanks. I was lookong in the parts book that i have and on the front pto it looks like there is some kind of a gear mec i was wondering what that was for ?

Will you be running the original CAT cylinders or modern cylinders? The old CAT ones were large low pressure designs where you can use smaller bore higher pressure cylinders if your pump can make the pressure. Of course the larger cylinders are physically stronger (larger rods etc) so they are very durable.

Just for comparison the standard CAT #44 control on a D2 turns 1525 rpm and makes 27GPM @1000psi. Max pressure is set to 1200 I believe, but operating pressure is lower. You could easily use a pump that made twice that pressure if you wanted and then you wouldn't need that much flow IF you had the smaller cylinders to match. If not, you better have the GPM!

I do not have the cylinders yet i am trying to gather info on what i should use on the project thanks Vern

30 - 40 GPM on a D2 is alot of oil for a d2 in my opinion. Back in the 1930's and 40's when hydraulics were using leather seals, and packing for rod seals and the max pressure was around 500 psi, you needed large bore cylinders to get the force needed. And because of the large cylinder size if you wanted any kind of speed out of it you needed the high GPM flow.

Not knowing what your project is, I am assuming you are putting a dozer onto a D2. One of the problems with dozing with a D2 is it is hard to grade with them because of the weight being too far foward for the amount of footprint you actually have, large cylinders add more weight due to both size and oil capacity.

Also another thing to consider is jerky operation caused by too much hydraulic flow for the size of cylinders on the dozer. Many times people will be dozing with a small dozer and either run out of power or traction and they will want to raise the blade, and even with the slightest touch of the hydraulics the blade has now raised 3 -4 inches dumping dirt, before you know it you have nothing but washboard.

Hydraulics are a little more complacated than just saying X amount of flow will work on your project. You need to first start with how heavy an object you are trying to raise, and then figure how much force is being applied to the cylinder at what angle, you also must figure how fast you need to raise this load, then work back to the pump.

I just finished building a tilt blade for my D46U, I started with copying the toolbar blade that is on my D47U and moved it back 6" and dropped the max height about 8" to allow for clearence with the radiator. I worked a lot of the articulation of the joints and angles out on proE cad modeling software.
I ended up with 3" Bore X 8" stroke cylinders with a pump that produces about 12GPM at 2/3 throttle. My pump was rated at 2500 Psi max and 2200 continous, but I have the relief set at 1800 psi, and I have more than enough pressure to lift the front of the tractor off the ground. This is using just cheep off the shelf hydraulics, nothing fancy.

According to my vintage Caterpillar product guide it says a D2 with a rear mount #41 hydraulic control would pump 28 GPM with a maximum working pressure of 800 psi.

Here is the info on the rear mount #41, and the front mount #41 totally different units, just same model #.

I'm guessing this is a front mounted #41 control on this one.
cgi.ebay.com/D2-Caterpillar-Dozer-Parts_...QQrdZ1QQcmdZViewItem

Yep CC that is the #41 front mount, the #41 rear mount looks like a BeGe pump, I can post pics if you need them.