ProZach

Here's the stuff you'll need
3 quarts of 75w-140
4-8 ounces of Friction modifier- if you have a LS
3/8" bare wrench
funnel
high temp red RTV silicone
some flat head screw drivers
steel wool
razor
drainage pan
1. Remove the fill plug using your socket wrench without a socket. The fill plug can be found on the opposite side of the differential cover on the driver's side. The bolt looks like a square peg should fit in it. You'll want to make sure this can be removed so you don't hit any obstacles when you're trying to refill.


2. Loosen all bolts on the differential cover and remove the lower six bolts. slide a flat head screwdriver between the cover and the diff and pry it open so that the fluid can drain.

3. Let all the fluid drain into the drainage pan. Remove the cover and clean off all old gear lube. I used simple green and some paper towels to clean it to a shine. Scrape off all the old RTV around the diff and around the cover using the razor.
4. Wipe off all the remaining gear oil that you can in the diff using rags and a paper towel.
5. Apply the high temp RTV silicone in a decent sized bead around the inner part of the cover so that it is the primary sealant for the fluid. Next trace a secondary line around the entire part of the cover making sure to surround the bolt holes to make sure that absolutely no fluid gets out.
6. Carefully put the cover back on making sure not to get any RTV on the gears as you're putting it on.
7. Lightly tighten the cover down in a pattern of jumping across the cover as you tighten the bolts. It should look like this.

8. Wait an hour and tighten the bolts about half a turn to a fourth more in order to ensure a sealed diff.
9. Fill the diff with the fluid and friction modifier until it is level with the fill whole.
10. Clean off whatever might have collected on the fill plug and tighten it back down.

ZaBree

Nice Post,
Mine was solid and then in the past 2 months I have noticed oil on it so it's about time to re-place it....

Where's the Craftsman Rachet....lol

ghostrider24

What are the parameters for changing the diff fluid? I have a 04 fx4 with 98,462 mile. Original fluid.

ProZach

do you mean you changed it and then it leaked later? or its just the original?
what's wrong with cheap no name brands?

your manual will say 75w-90 fluid but it actually should be 75w-150 you'll need three quarts and one 4 oz bottle of friction modifier.

intervals are every 100k miles or whenever the axle is submerged in water or if you notice a leak

techrep

iTrader: (1)

Step 1...remove the drain plug ??? Thats the fill plug...there is no drain plug.

bradseabridge

and not all diff's require friction modifier!

ProZach

Fixed, sorry about that, little bit of a brain fart.

Fixed- you'll find its now noted in the beginning steps of what you'll need

bradseabridge

Looks good!

bobkyle2

be sure to add friction modifier first... Inspect all gears and the ring for the speed sensor(thats what failed in my rear end).. Be sure to wipe out the bottom of the punkin..and theres a little cutout on the bottom thers a magnet in there clean it good with brake cleaner.. i actually spray everything down with parts cleaner.. in side there.. then wipe clean with a rag...


Good write up zach!!

ghostrider24

How often should this be done? I hear lots of ideas and I plan on using amsoil on mine. There's is 500,000 mile

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