You could run and get some Carquest diff oil, change it, run it, than use the real stuff (MotorCraft) when you get your gears done. . . I dont know, I'd just wait til you got the gears done

 

I am planning on changing the fluid in both front and back differentials either tonight or tommorow, How long after you seal the rear cover off do you have to wait to drive the truck? Did you notice any difference in gears changing easier, or better gas milage?

 

I'd let it cure for a couple hours.

 

As I was finishing mine it was getting dark, so I let it sit overnight. No leaks or seepage in over a year.

Don't forget to let the bead skin over before replacing the cover. I think that takes ten or fifteen minutes. Anyone know for sure?

I didn't notice any difference in shifting or gas mileage after doing both diffs. I did notice that the fluid that came out of the front was *ugly*. Looked like gray paint that had been sitting in the paint can for years.

 

Thanks for the advice fellows I went ahead and changed the front and rear fluids plus the engine oil tonight while it was cool outside its been to hot around here lately to do it during the day, I put Royal Purple 75W-140 in the rear case and 75W-90 in the front case, like F150NJ said the fluid that came out of the front looked very gray and nasty but the back was real clear looking which supprised me, I did everything like yall said to do it and drove it about 1 hr after I finished and it did not leak any at all, it also seemed like the truck shifted a little better, I took it out on the interstate and starting at the top of the ramp it did 0-60 in 8 seconds that is what the edge was reading, I didnt think that was to bad for a lifted gas truck what do yall think? once again thanks for the help on changing the fluids I really appreciate it!!