External pump or tractor hydraulics for backhoe??

[BobG_in_VA]

Sorry to say BobG, but I think you may have a problem with your particular set up.
As I mentioned in a previous reply, independent systems don't benefit from the thermal mass of the tractor's rear axle, or a heat exchanger in the radiator (not ALL tractors have that, but many do).
I think Surplus Center (Burden Sales) has a heat exchanger for very small money, about $20 IIRC.
You could probably get something like that plumbed into your hydraulics and radiator coolant circuits for well under $100 with hoses and fittings.

Just a suggestion, I'm not trying for "sermon" status either (-:

No mistake in my setup....I'm sure you wouldn't know this unless you had a Mahindra 6000...yes, I have a rear hyd line plumbed in, BUT, that model only has a 3 gal or so hyd res. as the trans/and hyd resevoirs are separate, and as such don't draw from the trans/diff. sump...sooo, you may now understand why I have a 15 gal res/hyd PTO pump for my 511.....As a matter of fact when I bought it new, and told the Mahindra dealer that I wanted the PTO pump, he said "That's the way to go with this unit"...As far as putting a heat exchanger on it, it doesn't get hot enough that I can't touch it...but with the res breather only about 3ft away, its not hard to smell it when it gets warm. I appreciate your input none the less. Not a sermon, just the facts...BobG in VA