Hmmm. The only thing I could think that would make your third run hotter would be if the lash in the gears weren't set right, as in the gears are running too close together. I don't know a lot about them, but I know that if the ring and pinion are set too close together it'll run hotter. They are supposed to be half check or just over...
Why is it you say the diff is running too hot?
My bet is that if you are still using the drum style e-brake that they are set too tight or seizing or something. I had a problem with my e-brakes seizing on or getting too tight from the self adjuster. It would roll forward fine, but it was a huge stress to roll it backwards, just like the brakes were engaged or something. Check the e-brakes cuz I never smelled anything burning either. Hammer the arms back in the drums and see if it loosens up. (They seize easy up here from all the salt they put on the road in the winter time.
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