even with stock subframe bushings, many 4.10 converts have gear whine to varying degrees. How many miles were on your diff at the time of the ring/pinion swap ? Drive (safely) at a speed between 60 and 70 mph, then report back whether or not you hear any gear whine. This is where it will likely show up if you have any. If you don't have any noise...on acceleration, deceleration, or at cruise, maybe that shop knows something that many others don't....and I need to send mine to them.