We leave from Taos headed to Amarillo tomorrow. I will pay more attention to the temperatures. On the drive axles, I would think that if it was an oil issue it would show up on both sides. If it was a bearing issue, I would think that some of the heat would migrate to the outer dual. I know that the outer dual probably has more airflow / cooling but surely it would not be the same temp as the drivers side when the inside dual is warmer? I would think that a dragging brake or other issue would create much more than a 20 degree delta.

Is your TPMS internal or screwed onto the stem? If the latter, can you swap sensors and see if there is a calibration issue?

Has this 20 degree delta been constant, did it just show up?