peerless 739 transmission problems : advice needed

hey i need a bit of help with a transmission . its a 739, 5 speed peerless gearbox . when in any gear it "lugs" . i took it apart and overhauled it , but there was only a worn bushing. I replaced all of the steel-alloy (it was off of a john deere 68) bushings with brass oiled ones and re-filled it with 80-w90 gear oil put it back on and it still lugs . what i mean by "lugs" is it pulses in speed when my engine is running constant rpms but i do not hear any grinding of gears ,and i know what that sounds like because i have went thru 1 other gearbox when the bearings went out . . idlers are all good and just put on a very good belt . if y'all have any ideas please share them !!

it acts like it poping in and out of gear but no noises? I have one doing that. I havnt torn into it yet so i cant help... but id like to know if you fix it what you did.

so i replaced a clutch pulley just to see what that would do and i havent noticed any pulsing so far, but ive only driven it for like 10 minutes since i did that . i hope i fixed it though!!