So I have a 04 fx4 and I wanted change the fluids in the truck so I went to the dealer and got the fluids there. They gave me Mercon V to do the transfer case even though the manual stated mercon, and also they gave me 75w-140 for the front and rear diffs. Are thoughs there right fluids. Also what do you guys use for the seal in the diffs just rvt or do you get a gasket and use rvt. Thanks.

 

heres how you change the rear fluid:

i just got changing my fluid (8.8). I spent a long time on it because i worry a lot. I did this:

-took the cover off, covered the gears up with a plastic bag
-scraped all the sealent off the cover and the rear end, i even used a wire brush and got every little bit of sealent off
-made sure there was no oil anywhere on the mating services
-put a small bead of permatex gasket maker on both sides of the gasket, i circled the bolt holes
-put the cover on and snugged the bolts just so a tad bit of sealent popped out
-i waited 1.5 hours and then snugged the bolts a little more and filled her up
-waited a little longer and torqued the bolts to 33 ft pounds.
-cut the excess sealent that oozed out
-cleaned the back of the lid and surrounding areas with degreaser (to make it real easy to tell if i had a leak)
-NO LEAKS SO FAR

I think the trick is to put the sealent on, snug it down and leave the truck alone for a while to let the permatex seal.

EDIT: I used the red permatex, so different then the black except 150 degrees toleration.

As for the right fluids, check your owners manual. If you have limited slip then you will need friction modifier for the rear

 

Front Axle takes 2.114 quarts (2 liters) of SAE 80W-90 Premium Rear Axle Lubricant.


Transfer case takes 2 quarts (1.9 liter) of MERCON® V Automatic Transmission and Power Steering Fluid.

Motorcraft® MERCON® V is a premium-quality automatic transmission fluid designed, engineered and recommended by Ford Motor Company for use in Ford, Lincoln and Mercury vehicles that require either MERCON® V or MERCON® type fluid. This product also provides excellent performance in electronically controlled automatic transmissions.

 

Just changed oil in my 9.75 last week.
1) took out bottom bolt
2) took drill with a 1/4 inch bit.
3) drilled all the way thru housing.
4) let oil drain.
5) put silicone on threads of bolt and screwed back in.
6) pulled out plug on pumpkin
7) put three quarts of Royale Purple 75/140.
8) cleaned plug and resilicone it, tighten plug.

took less than 1/2 hour to do this!

 

Mercon V is for the transmission. Even the newer owners manuals, 08 and 09 say to use other than Mercon V for the transfer case.