JX75 transmission clicking when push forward

new to me 9 year old JX75, re and re the pinions (smooth work as should) but when i push the mower forward (without tranny engaged) I get a click/stall it seems at the same point with every wheel rotation. I've checked the spring attached to the clutch and the plastic clutch lever seems to move fine. I'm thinking it is internal but reluctant to open up the transmission. Looking for a manula/schematic of the transmission or ideas. Feels like a gear is not completely disengaged. When transmission is engaged running it works perfectly. Ideas? thanks

you should get a clicking sound when pushing forward w/o transmission engaged, that's the sound of the ratchets allowing the wheels to turn while the axle is not turning. perfectly normal