I have a Marcotte redrive and it was mentioned a while back that the Marcotte redrive needed an external tank for cooling as the sump has 80 hypoid lube in it.  I'm not sure that a tank would help much for cooling.  Does anyone have the knowledge that I may need to install an oil cooler of the automatic transmission type to keep the gear box temperatures under control.  I am of the opinion that the oil will thermo siphon thru a cooler, is this correct.  Thank you in advance.  JohnD