A little different point of view.
The over heating you see is due to the sliding action of the pinion on the ring gear. A spur gear is said to lose 1% power at each mesh point. A helical gear will lose 2% or more, depending on the helix angle. The pinion/ring combination will lose 4% and more, due to the large helix angle and amount of sliding action.
A variety of techniques has been developed to decrease the the friction loss at each mesh point. F1 and other competition cars have been using these techniques for some years, and it is becoming popular enough so that some of them are commercially available at reasonable prices. One process is called REM and is a post production finishing process.
http://www.evansperformance.com/rem.html
On a race car, if you consider the cost and effort to install and plumb a pump, oil lines, and radiator, the cost of the REM process is less, with the side benefit of getting a small increase in power at the rear wheels.
The effect of using this is to obtain a substantial decrease in oil temperature, since less power is being lost to friction.
Studies I have seen seem to indicate a reduction in friction of around 50%, with lesser decreases being observed at light loads and greater decreases being observed at higher loads, just where you want it.
The REM process is licensed to third party shops, so is available from multiple sources, both in the US and Continet.
Remember, there are multiple sagas of magic treatments pushed by various classes of snake oil salesmen. Some race teams believe in one treatment, some in another, some in none. Do suitable due diligence to see whose lies you believe.
David
1968 36/7988