Hello, I am of recent admission and I will give you my opinion: if the buzzing and falls of intensity when accelerating and decelerating but it does not present it being detained you are right are the outlets to the arrows in the differential considering that the transmission is not skipping or making wrong changes that could take us to the brake barks of the drums, the turbines are very rare that they do They work or the car has no traction, it can be diagnosed with an oil Teste de pressão de qualquer maneira a transmissão deve ser removida do caminhão e desarmar, antes disso, verifica se não será uma bulteria de roda