Never did any tranny work on it. Remember, the 3/4 ton has a closed drive shaft 1/2 way back and ends at the carrier bearing. From that point to the differential, it is open. Interestingly, once I let off the gas and the noise starts, it will stop abruptly as I slow down. I've had pinion problems before and this doesn't sound like it. Typically, when you have a pinion problem, it is consistent. This isn't. It does happen about 3/4 of the time.
Never had the lid off. Only changed the fluid.
