Friends truck, 2019 Ram 2500 with the 6.7 Cummins, bone stock with 45k miles. Its either hooked up to a gooseneck hauling stuff or pulling his 5th wheel camper that weighs around 17k loaded, 95% of the time. I change the oil every 8k with Delvac 15W40 and a Napa Gold filter, fuel filters every 15k, and air every 30k. I told him we should start changing the tranny fluid and rear diff fluid every 50k and he agreed. I know it calls for 75W85, I was thinking of using either Redline 75W90 or 75W110, or should I stick to the 75W85? Im not sure if he has the AAM 11.5 or 12.0 axle, Ill find out. Also Id like to find the torque specs for the cover. I think its 30 lbs but some have reported bolts snapping at that torque.