You may have come across the same problem I did - the last place that did my diff fluids used airtools to put the diff plugs back in and overtorqued the plugs. I stripped the rear fill plug trying to break it loose and (a few eeks later) Saltus helped me by welding an extension to the plug and then we used his airtools to get the plugs out. I needed the 200+ PSI line to get the front drain plug out.

The only plug I could get loose with a breaker bar was the front fill plug.