can anyone help me with a vibration in my 74 c3 350 Muncie 4 speed, at 3500 RPMs in each gear it vibrates badly through the transmission and through the car. I’ve had some people say it could be the half shaft joints, but I think that would increase with speed and continuously get worse the faster you go. My vibration is only around 3500 and up and in all 4 gears each . When I am sitting still and the car is in neutral and I raise the rpm slowly all the way up to 5500 rpm I have no vibration, any help would be great