CarbonSteel
Well-Known Member
I would up the viscosity in the rear to 75W-140 and the front to 75W-110 (which was the upper viscosity that 75W-90 used to be before the SAE J306 tables were updated some time back). The CRAZY thing (at least on my axles) is that I have the towing package on my Rubicon and an M220 rear axle, yet it was filled from the factory with 75W-90. I also added temp gauges for the front and rear and have seen 202°F in the rear axle driving at 75ish in 90 degree weather. Because lower gear ratios (higher numbers) generate more heat than higher gear ratios (e.g. 4.88 creates more heat than 4.10), larger tires increase the load on the axle as does towing, and considering the small capacity of the M220 (1.6QTs) and M200 (1.3QTS), I would not use anything other than synthetic oil.i just passed 13k on my 2018 JLUS. didnt realize i should have done a break in change for the diff oil. i did for the engine oil.
i have the LSD/M220 rear. should i use the factory spec of 75w-80 or jump to a 140. i do offroad it and am on 35s. took it out this past weekend.
i see 4wp around the corner from me has Dana Friction Modifier in stock. from what ive read online, theyre pretty much all the same. sound accurate?
https://www.4wheelparts.com/p/dana-...iction-modifier-additive-43161/_/R-FSGR-43161
I recommend Amsoil Severe Gear oil as it has the LSD additive already in it and is arguably the best gear oil on the market today--but with that said, there are plenty of oils out there that give great service life. I would not hesitate to use Castrol, M1, Valvoline, Red Line, Royal Purple and the list goes on...
Hope this helps!
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