I am curious what you are looking for.
Just looking at the parts disgram it appears the shuttle valve is fed by a prority flow divider. The loader is on the excess circuit?
Dan
On these tractors when something is wrong / off it will cause you to lose either the loader / three point function and or PS function.
On my GST when the GST system has an flow issue you will lose PS use.
On a DT with a shuttle issue it will do the same things.
When it's a pump drive or suction issue you can lose both.
It's a simple diagnosis point on these systems to give you some path of what to check.