I would start by pulling the shaft & moving the ujoints back & forth in their planes of movement & checking for roughness. First see if the straps are a slight bit loose/quick visual on the ujoints when you get under there. fluid level/freeplay on the yoke (not sure if that would produce noise but it'd take 5 seconds & then you'd have that info if others say it is critical). EDIT trans mount in good shape/bolts tight