Noise in 4th and 6th gear Help!

[gcamp]

This is making me want to pull my hair out.
I have had this noise for about a year. It sounds alot like a hydraulic valve chatter more than a grinding.
When I got the tractor it had transmission damage and I have replaced bearings, drive shaft, secondary shaft, main shaft and the 1st & 3rd gear.
The shafts and gears were the obvious damage.
Now, it made the noise when I re-assembled, so I split the tractor, gutted the transmission and checked for problems. Found a metal chip and bad PTO output shaft bearing (up front). Replaced that bearing (again) and the noise is still here!! It only shows up in 4th or 6th and usually between 12 and 1500 rpms with a small load (incline, acceleration or trailer), and sounds like it's under me.
Has anyone else had this? Any suggestions?

Thanks,
Gene

[GERRY]

hi dont know if this will be of any help but i had adexta which would make a noise when
going downhill , never did find out what it was , but was informed that
fordsons could make noise even from new in this area , there is a post on the old site.
i think it is called funny enough noise in gear box Gerry