Well, got some progress...
Thanks to all who provided your inputs, it certainly narrowed down some choices.
I was able to source a replacement chain shaft coupling hub (that's the official name
) to change the shaft size input from 9/16". I grabbed a 5/8" shaft at Brown's Bearing in Spokane and went home last Friday to start shopping for a pump but it turned out that I really needed a 1/2" because the pump size I needed only provides the 1/2" shaft in the SAE AA 2 bolt configuration that the B7100 requires.
Looking into it deeper, I wanted to really find out what the original pump size is and I found the formula to calculate it "in reverse" so to speak. It involved taking apart the pump and taking 3 measurements inside. After calculations, I found that the pump displacement is 0.275. Pretty stoked now that I can source the right pump and found one that would fit the bill, only a smidgen bigger with a 0.31 displacement. I'm wondering if going to the next size up at 0.37 would bog down the engine. The max RPM is 4,000 (rated for 2,000) and from what I understand, the B7100 with it's D750 engine puts out 2,900 RPM.
It's here:
http://www.surpluscenter.com/Hydrau...cu-in-DYNAMIC-GPF1051PA-HYD-PUMP-9-7767-D.axd
The gear itself is a "4012" gear, I have one with a 1/2" shaft keyway coming from Brown's bearing and I'll be returning the 5/8" for it. Cost is only $11.75 plus $9 ish for shipping. The chain isn't proprietary as a quick search on the internet shows many various chain combination.
The only question that remains is if the shaft length combination will still be ok as the new sprocket is a little longer than the original and the pump shaft is shorter. I may need to get "squiggly" with it so I should know once the two arrives.
Pics will follow, plus a write up that includes all the parts I used for it.
It should be interesting how the loader & tractor will react with the pump that's slightly bigger than the original.
Think I'm wise in picking the 0.31 pump size?