Last week I had the u-joints replaced by a local mechanic that used a driveline shop to install them and balance the driveshaft. While in for an oil change at the dealer I had the rear differential fluid changed, as well as the transmission fluid. Since that time I have heard a "grumbling" sound from the rear end, even when going straight and a rubbing sound when I make turns. I also get popping sounds from the underbody at low speeds, e.g. backing up and down the driveway. I am taking it back to the dealer tomorrow. Could this sound be a result of the fluid change?

The CRV has 87,300 miles on it. The first fluid change was at 63,000.