6400 starting issue

Thought it was the battery, replaced with oem battery. still only getting buzzing, intermittent drained cranking. Replaced starter with oem starter. Still same result, have moved ground around via jumper wire, have gone hot to the starter with ground to starter housing and still the same. Ground to the block good although have not checked that the cable itself is 100% but both ends look great. Do get some clicking from the fuse box.
What am I missing???

Tractor is late model 6400 cab, less THAN 1000 hours on it.