I have a 644H will not pull its self in drive or spin wheels when pushing in first gear. Changed fluids and filter. Looking for pressure specs
Zf trans, that's the best people to talk to. There is a tag with a model # on trans. Google zf industrial, I can't think of name of out fit i've called before. Your problem sounds like torque converter.
As a Deere factory rep once told me, Deere was so impressed with the ZF transmissions they went out and bought Funk. I wish you better luck.