Originally Posted By: tdi-rick
Originally Posted By: Jim Allen
BTW, another way to be able to run a thinner oil for more efficiency without overheating the oil is to run a fined cover. More capacity doesn't by itself reduce oil temp (though it does dampen temp spikes and slow the rate of temp rise) but a finned, high capacity cover has more surface area for cooling. In my own case, such a cover reduced max oil temps by ~15-20F and that's one reason why I can run 90 grade and still tow 10K pounds while staying under 220F. I occasionally see some spikes higher but in the areas I go that is very seldom, of short duration and never over 240.
I went the other way (xW-90 to 80W-140) purely as the rear diff now sports an 8mm nodular iron cover and so won't dissipate heat near as effectively as the original tin cover.
I'm not sure I really want to know how hot the diff gets now, it would take skin off my thermally calibrated finger when it was still only using a tin cover.
Remember also that the more heavily hypoid a crown wheel is the more heat generated.
A centreline spiral bevel design runs significantly cooler than something like a Dana 60 or Ford 9".
Steve, what car ?
Ford and Holden spec 80W-140 as the Dana diffs are smallish with lots of torque going through them.
They also seem prone to bearing wear too.
BA Falcon wagon with complete new rear end. Went from a M78 3.23 stocker to an M80 3.46 4-pinion LSD all brand new. Oil is VP Fuels 85W140 which is supposedly full syn and obsolete product. Very interested in diff temp guage, just need to see who sells 'em.