680 Won't start.
 

The 680 I got for my friend won't start today. I thought the battery was weak so charged it and came back and still no start.
The driveshaft is very hard to turn. Could one of the hydro relief valves be stuck?
I drove this tractor off the truck a week ago.

So I take it that i just won't turn over with the starter, even with a jump? If you suspect the hydro, quickly disconnect the driveshaft from the hydro charge pump end and see if cranking improves. If not, you could still have such a weak battery that even with a jump pack or cables, it won't crank the engine over. Could also be a weak starter.

I cannot turn the driveshaft by hand
Battery was charged and tested.

ALL, my Hydro Tractors are hard to roll the engine over, by hand.

Starter gear is prolly engaged on the flywheel, turn the shaft anti clockwise and it should let the gear retract from the flywheel, if not you may have a mouse nest in there.