01 Ford F-250 SuperDuty 4x4, lifted on 35's. Rear end has 4.56's in it (new) need to change oil since break in. Tow pig, work truck, gets beat on a lot. In the Texas Panhandle, gets pretty warm, and pretty cold. Anyone know the ins and outs regarding differential/gear oil? I think factory weight is 75w-140. Should I stick with that? Go a little heavier in the front, maybe 75w-110? Trying to find out what my best bet would be. Any knowledge is appreciated.