Since there was plenty of snow forecast for the local pass during the holiday weekend, I decided to load the family up in the 4Runner for our annual trip over the mountains to grandma's house. As we neared the pass and the snow began to fall, I took an exit and stopped briefly to lock the hubs (I left the transfer case in 2WD). After driving on the freeway for a mile or two, I could hear an intermittent howling/whirring noise from the right front. The noise quieted with a reduction in speed and was mostly silent as I came to a stop to investigate. I found the passenger-side output flange on the front differential seemed to wiggle much more than expected when compared to the driver's-side. It seemed to be fully seated in the differential and did not slide in and out, only side-to-side perpendicular to the axis of the shaft. With the hubs again unlocked, the noise was gone. I later re-locked the hubs and engaged 4WD for some very slow going on compact ice and snow while driving around the summit without any problem. I did not try any more driving at speed with the hubs locked. Is there a bushing in the differential housing which may be worn or a likely problem with the flange? Any other ideas?

Thanks,
Isaac