Join Date: Jan 2006
Location: Northern California
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Just for sake of information... My differential temps are generally around 175*-185*, driving on the freeway. Speed has a huge determination of running temperature over weight. Meaning, if I'm doing 75 mph for 30 miles or so on a cool day the temps will be in the 150*-160* range. On a warm day I'd expect diff temps to be around 185* or so. Towing heavy in triple digits doing no more than 60 mph the temps might climb to the 190*195* range. Towing up long grades the temp hasnt climbed over 210* and once I crest the grade they quickly drop back to the 195* range.
I've been running 75-140 for the past 5-6 years or so and have been told by a few oil manufactures that I may see a 10* reduction in running temperatures if I used a 75-90. But...I'm not willing to give up the high temp protection during towing for the reduction in thermal buildup from viscosity friction.
And just in case anyone doesnt know... lower range differential ratios will always run hotter due to the increased hypoid action.
'01 2500 Sport 4x4 5spd w/Fastcoolers, Mag-Hytec, EZ, RV275's, 4" w/o muffler, South Bend, Steering brace, aFe, 2 lo kit, Isspro Boost, FP, and EGT on pillar, Westach Trans/Diff temp gauge in dash pod, Raptor 100 w/ 1/2" line, Pac Brake, Rancho 9000, 285's