trx4 gearbox screech with axe 550

hello, i have a trx4 and put an axe 550 3300kv in it, ive noticed that recently its started making a screeching noise at walking speed, and its louder than usual, gear mesh is correct, gearbox had maintenance, so have the axles, my only guess would be that the pinion might be badly made, its not the stock one you get when buying the axe, so maybe buying the original axe?pinion might help? any ideas?