Working on a 630 with a gear noise under load. Removed 1st reduction cover, sliding gear shaft and countershaft. Didnt see any bearings out or loose. The noise seems to be coming from the 1st reduction gear cover, but the bushing and outer bearing seem in good shape. We bought used belt pulley gear and 1st reduction gear, same noise. When going up hill it just screams, but coasting down hill quiet. We put the tractor on jack stands and ran it, applying the brakes to simulate a load, same loudness in each gear, but different noise or pitch. Reverse is quiet, could it be the countershaft pinion? Thanks