I think the temperature of the t-case/oil would go up if your using 4-lo/offroading vs driving in the street in 2hi. I say this, because after driving on the street, I can the t-case doesn't get very hot, I can usually touch it with my bare hands.
Just a guesstimate...probably not more than 125F when offroading. I'm sure tjkj will chime in and give you an exact degree... +/- 2 or 3F!!
P.S. my t-case is up for service in the next 1-2K miles or so....I'm still contemplating if I should do this. What materials (fittings, hoses, etc...) are you looking at using.
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2002 Jeep KJ Sport 3.7L 4x4245/75-16 Mastercraft Courser HSX, 16x7 Cragar, 2" OME MD Lift, ARB Bumper
AEM Brute Force Cold Air Intake, Flowmaster Super 44 Muffler
Currently working on: Full service on transmission & bed-lining ARB bumper
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