I think Dynamating just masks the problem. PBR had the whining gears problem (like many of us do) because of bad gears, bearings, etc. He had all that replaced and now no whine. I believe I have the same problem, but have elected to try changing the gear oil. Least expensive procedure first. I have a feeling this won't work at all because I've had a similar situation happen before with another vehicle I own and the whining problem just became worse as I went along until eventually I had to replace bearing, gears, etc.
By the way, does anyone know what kind of an axle we have? It doesn't look like a GM axle, but more like a Ford 9 inch rear end. Of course I've only seen about 1 or 2 before anyway. (GM guy usually)