So I've been off roading quite a bit lately, ever since I put new coilovers and shocks along with lift on the truck (2022 3.5 EB). I do a lot of 4x4 mode in 4H and I've read that after about 500 miles of front diff being active is to do a fluid change. Hell, my rear end probably could use a fluid change too, I have almost 20k on the truck. My front diff seems to be easy to access after putting the lift on it (see pics below). Would I just take the cover off to drain the fluid, same as on the rear, and then put a new gasket on, then fill it up at the fill hole? If so, which gasket is the go to?

Also, what about the transfer case and do I need to change that fluid as well?

 

You wont hurt anything by changing the fluid and if you want a maintenance task to perform then go for it. Working on stuff is fun usually. But its not necessary. I would put it at low priority. Tons of trucks may see 1 change in their lifetime and probably only because a seal leaked eventually. My opinion its a maintenance item but not necessary at 20 unless theres a concern about water in the diff.

500 miles in 4H isn't excessive. In some parts of north america people may keep it in 4H for a few months at a time. I dont know why it would cause gear oil to break down or be consumed or damage anything or any other reason it would need changed at such short intervals. Maybe there is but that doesnt make much sense to me.

 

Agree that the interval is early, although much like early engine oil changes, it won’t hurt a thing. If you do proceed, I’d change the transfer case oil as well so they’re all on the same interval.

 

Front Diff:

Rear Diff:

Transfer Case:

 

Why don't all differentials have drain plugs? I get that 90% of the population would never use them, but it would make things much easier for the 10% of us that would.

 

It is a money thing just like the trans pan doesn’t have one. Ridiculous if you ask me because it would also make easier for the mechanics.

 

I would change the fluid. I had my 3.5 eco, 9.75, 3.55 changed at about 7k only because my '01 F 150 bearings start to burn up at 30K. I could smell them every time I opened up the tailgate, and eventually had to replace the bearings.
Assuming you have a 9.75 Ford makes a gasket for it, part number HL3Z-4036-A. Although you might be able to reuse yours. My '21 3.5 eco has a 9.75 and it came with a gasket installed from the factory.
If you have a Super 8.8 Mag Hytec sells a gasket made by Lube Locker. Lube Locker makes a gasket for the 8.8 which looks like is what's on your front axle. 75-85 Synthetic Hypoid Fluid is what your axles should take.
You could also use a vacuum pump, catch can setup without removing the cover.

 

the gasket on the front diff seems to be that liquid resin or however you would describe it, that dries up after you apply it. so i would have to clean that off and put a gasket on. just not sure which is the recommended brand. come to think of it, its the same on the rear diff. i'll check out the mag hytec brand.

 

In the Marine Industry it's pretty common to use an oil pump to change oil. There's often times no room or no way to get to the lowest part of the motor so you pump the oil out. Easy enough to do with differentials too. If the gasket is still good, why not just leave it alone and pump out the oil. One can always add a little oil and pump again if you're worried about getting all of the old stuff out and 'flushing' it a bit. I've done this with great success in older 4x4's where there was no front cover on the front differential.

 

What size rear axle do you have, 9.75 or Super 8.8?
Super 8.8 is a 12 bolt like the 9.75 but has two notches/ indents on the right.
Check it, if it's a 9.75 there is probably a gasket installed.
Make sure all mating surfaces are clean, no old Silicone.
Ford sells a Silicone Sealant, TA-29. One hour dry time.
Permatex also sells a Silicone Sealant for Gear Oil, 81182. 24 hour dry time.
Changing the front diff fluid on your truck looks to be a mess with that hunk of metal under it. I would probably use a gasket on that. You should not smear the wet silicone as you put the cover on.
If you do Silicone the front you might want to get (2) 10 x 1.5 mm short stems to help guide the cover on. Then remove them after you hand tighten the other bolts and the install those two bolts.