I only have trouble with heat when I am above 50 miles an hour for more than an hour in the hotter parts of the year...in the dead of winter, I dont think I have ever seen the gauge get over 150.
The diff pump and other pumps used in industry for heavy oils, can be gotten for a bit of cash...then theres a cooler and lines and whatever you need to run it and hopefully a thermostat so you dont try pumping gear oil when its -20 degrees outside and the stuff couldnt overheat if it wanted too...the whole drivetrain is noticeably held back by the heavy stuff in all the gear boxs and diffs at temps below 0...I run 75W-90 Eaton synthetic lube. Since many have reported that they have run 60 MPH or more for hours at a time, it seems that the expense and work that go into doing a cooler would be better directed to correcting the discrepency in the case that causes it to overheat...less to screw up in the long run and less to haul around...plus it would be stock, if that matters, instead of modified to try to band aid a problem...then also there is the long term viability of using a pump/cooler instead of removing the problem causing the heat...will to tight bearing clearances or other problem(s) in long term use cause problems that will eventualy cause the t-case to need a rebuild or a change to a different case, like a 205 or something...if it is rebuilt correctly, as has been shown by several members, the cooler/pump would be unnecessary...if a 205 or other was used, same story...
Like in Apollo 13....Lets work the problem people!!
brute4c