Transmission issues? on 1993 Nissan Pickup (D21)

Hearing gravely noise when driving in all gears except fourth and only stops completely when clutch in. Had transmission bearings replaced last year, same noise as before just not as bad!!???

If a transmission makes noise in all gears except 4th the problem is in the lay shaft bearings (usually rear lower bearing in the case. The reason why the noise goes away in 4th is power gets transmitted through the input shaft straight through the out put shaft when in 4th and does not pass through the lower shaft in the transmission. Ensure oil is in the transmission, perhaps drain and refill the gear box but damage is done!