IMO, running 51/20 is over geared with UE Diffs. You should be at 16 or 17 pinion with mod 1. You will find your sytem much much happier. The temps calculations is an estimate only, and not ALWAYS the case. Another problem could be a connection somewhere as well. Also, you are running a ubec correct?
"if you've got something to say, say it peacefully"