Ok guys, first I have to give credit where credit is due. Quintin wrote an excellent article on how to change your axle bearings and seals for his 04.

https://www.f150online.com/forums/ar...lots-pics.html

I consider myself a pretty good shadetree mechanic but am no ASE certified tech like I assume Quintin is. I replaced mine on my 03 in the driveway. So here’s another “how to” to help.

SAFETY: Make sure you shock your front tires. Then jack up your truck securing it with jack stands. You have to have your trans in neutral so you can spin your gears later on, so I went ahead and did so after it was secure on the jack stands.

Remove your wheels. (sidenote: Quintin advised that the wheels are 21mm. My 03 is not as I even went to the parts store and bought a 21mm socket as I couldn’t find mine. Mine must be a 22mm. I didn’t have that either so I just used a 7/8 and was fine.

Remove your calipers by removing the 2 10mm bolts. I tied my calipers up with some rope to prevent any strain on the brake lines.

Here’s my diff leak



Here’s my passenger side with bad bearings and seal leak.



Driver’s side



More diff leak





Close up of passenger side leak



Close up of driver’s side



Remove rotors (passenger side)





Driver’s side







Remove the 12 13mm bolts holding the diff cover on. (For 9.75 rear end) It is best to remove most of the bolts leaving 2 or 3 at the top so most of the gear oil can drain and prevent a big mess. Make sure you have a pan underneath to catch the oil. I cut down a Rubbermaid container I had and it worked perfectly!



Note the “373” indicating my 3.73 gears



Inside the diff





Rotate the gears around so you can remove the pinion shaft and pinion shaft retaining bolt.



Remove the C-clips and then slide each axle out. Put the pinion shaft and bolt back in to prevent the spyder gears from moving without the axles in!!
Now you are ready to use the slide hammer and bearing removal tool. I borrowed one from Advance Auto but it did not have the big washer and nut to tighten up against the bearing. So, I had to take a trip to Autozone and borrow theirs. I actually chose one adapter that was too big. I was slamming away and the bearing wasn’t moving. I removed and noticed that I had actually gouged the inside of the axle housing some. I went to the next size adapter down and eventually got the bearing out.

Passenger side



Notice the burrs



Driver’s side

 

Now you may be wondering why the axle deal is on the slide hammer with the bearing. It’s because the seal removal tool was cutting through the rusted seal like a can of tuna and I had to hammer both the bearing and seal together.

I did the only thing I knew to do on the passenger side to get the burrs out. I put a clean rag inside the axle housing past the burrs. Then I turned the air compressor down to like 25 PSI and took a die grinder to it taking the edge off and smoothing them out. I then took another clean rag and kept wiping until I didn’t get any more metal shavings; as I didn’t want them ending up in my gears!







I also scrubbed my diff cover with a scotch brite pad, razor scraper and brake cleaner. Then I painted her black.



I was also tired of the surface rust on my rotor hats. So I painted them as well since I had them off.





Now it’s time to put it all back together. The parts:





I did not have a race driver set, so I did as Quintin advised and just used an old bearing. I also used a block of wood that seem to help as well.

Driver’s side



Passenger side



Now you need to clean you diff cover and get all the old sealant off as well as the axle housing it mates to. I cleaned my diff cover bolts as well with brake cleaner.



Now you need to remove the pinion shaft and retaining bolt you put back in (You did put it back in didn’t you?!!!!)

Slide the axles back in and remember to put the C-clips back in. I had a little trouble on the passenger C-clip for some reason. I fiddle with it and eventually got it. Now pull your axles straight out on both sides. Now you reinstall the pinion shaft and pinion shaft retaining bolt.





Put RTV sealant on your diff cover and bolt it up. Some have recommended waiting an hour before adding the gear oil while others advised you could put in right in. I decided to wait an hour as it couldn’t hurt; and it ended up being like 2+ hours as a neighbor came over and we started talking.

My hats look good!



Now just put your rotors back on, then you calipers.

Passenger side installed





With wheels on





Now I will say that the owner’s manual and Haynes manual LIE about fluid capacity. Quintin advised it takes a little over 3 Qts. I thought with his truck being an 04 and mine an 03 something was different. I went by the owner’s manual/Haynes manual. After you convert their PINTS to QUARTS, it is 2.75 Quarts for the rear diff. I put in 3 Qts of Royal Purple 75w140 Synthetic gear oil and it is still not full. It is not coming out of the fill hole and I don’t see it either. I even had to transfer the 3 bottle into one after I got most of it in so I could squeeze more into the diff. That horizontal fill hole SUCKS!!! I went and bought another quart today (1 for the rear and went ahead and bought another one for the front diff I plan on changing today). SO another lesson learned: TRUST Quintin!!!

Another tip: Don’t do this with a 105 heat index like I did yesterday. I got sick at one point and had to take more breaks. Overall it took me about 8-9 hours with trips to the parts store, about an hour lunch break, numerous water/cool down breaks, taking pictures, doing other tasks like painting my rotor hats and diff cover, and clean up.

So I hope this helps-----DirtySCREW

 

Thanks for the write-up. I'm jumping into this project in a week or two, and your tips and tricks will come in handy.

 

i cant belive tht he has the FX4 offroad package and he has a open differential.

 

I'm no expert on diffs, but according to the all the Ford dealers I give my VIN and diff tag to they say I have Limited Slip. I believe I have LS from driving as if I'm on a dirt/rock road and gun it, it leaves two "burnout" marks and not one. Can you elaborate? How can I knwo for sure?---DirtySCREW

 

I'm wondering what makes him think you don't have LS.

 

Theres not a big "s" spring in the middle of the spider gears, so i always thought that means its a open differential. Heres a pictire of what i thought a lsd was suppose to look like. please corect me if im wrong.
http://image.carcraft.com/f/9256030+...mited_slip.jpg

 

Easy enough to test - put it in neutral and jack up one rear wheel and try to turn it. If it turns easily and the driveshaft turns, it's an open rear. Make sure the ebrake is off.

 

yea it is easy to test but sorry if im wrong. Thats just what i always thought they are suppose to look like and i also read something one time that before 2004 the trac lock differential or LSD was a option on all the trucks including the FX4 but it didnt come standard untill 2005 or later.

 

My 07 did have a LS diff before I put in a Detroit Tru-Trac and it did not have the spring in it, just the friction discs behind the side gears.

 

Thanks for the reply im glad you said that cause i dont want yall to think im a know it all cause im not im wrong alot and im glad to learn im only 15 and hope to become a mechanic one day.

 

Take it to the bank,,,ONLY the 8.8 uses that S spring on posi units. 9.75 diffs uses friction as Sam has mentioned.

 

Something else I forgot to mention guys:

Ford recommends a bottle of Friction Modifier for those that has Limited Slips (like me). Royal Purple & Amsoil say they have friction modifier already in their fluid.

Now this is the debate of the century as far as whether or not you still need to add the Ford modifier or not.
FOR ME----I plan on driving the truck awhile to see if she feels any different---all-be-it minus the parasitic drag I was feeling from the bad bearing (that I can tell is already gone). If I think I need it, it can easily be added by removing the abs sensor on top of the diff---DirtySCREW

 

If it doesn't chatter, you don't need modifier.

Add it through the fill plug.