[PbFut]

I am not familiar with what you choose. A little late to the party. I ran a Jerico dog box in a road race application about 12 years. Refreshed every 2 years and oil changed at about 3 to 5 hours use.. Should have been more often but $$ always an issue. I experimented with 4 different oils. All 75-90. Thicker will affect you shift speed and ease of engagement, very critical for my use. Royal Purple was black. I did not like the results and feel it is a marketing product over real world result. Red line has a product that claims it fights gear crash. I bit, given critical for dog ring syncos It was ****. Mobil One performed quite well and price is decent. Hands down the oil that performed the best was Valvoline. It comes out as gold as it goes in. I use 75-140 in the diff. I do not have a cooler on the diff. It is a clutch style with ramps for the spider gears to walk on and tighten as torque is applied. Great for loosening in a corner, slipping the 5 clutches and then tightening down on corner exit. This allowed rotation in the corner and lock the differential on excelleration down the straight away. Lots of heat. The Valvoline 75-140 would pour in gold and out nearly the same color. I ripped a bunch of teeth off, and twisted splines but never a oil or heat failure. So Valvoline is my go to brand in all 4 of my cars and truck.