Changing Differential Gear Oil

[MountainMan]

I have a 2006 F-350 4x4 with 26,000 miles on the clock. Last week I switched to Schaeffer's fully synthetic 5w-40 CJ-4 motor oil and am now thinking of changing over to fully synthetic gear oil in both front and rear differentials as well as the transfer case. Is it too early to switch with only 26,000 miles? When do most of you change your gear oils?

[tuckman]

25k sounds about right for diffs and t-case.
Don't forget some friction modifier for the rear if you got a lsd, some say you don't need it using syn oils. My experience says you still need to add some...just not as much as you do using dino oil.

[6.0ops]

The factory oil is synthetic and supposed to be "lifetime" lube. I just changed my rear diff at 110000 miles with Valvoline 75w140 synthetic, and I didn't add any friction modifier (05 F-350 4x4 w/lsd). I'll change the front soon but I've never been in deep water so I'm not to worried about it. I changed my transfer case at 90k with Mobil 1 atf.

[LHMissions]

Dumb question here - but how do you fill the T-case after you drain it? I've never drained it much less looked at it so just looking at it could answer my own question but since its 40 miles away from me right now - well - is it like with the differentials - a little fill plug?

[Evil Eye]

Originally Posted by LHMissions

Dumb question here - but how do you fill the T-case after you drain it? I've never drained it much less looked at it so just looking at it could answer my own question but since its 40 miles away from me right now - well - is it like with the differentials - a little fill plug?

Yes. There's a little fill plug.