My rear differential service - with pics
 

I serviced my rear differential today, and installed the Ford aluminum cover. I have 60k miles on the truck, and I tow frequently, submerge the axle occaisionally, and so I think it was due for service. I took a few photos and want to share them here. I used Guzzles guide found in the FTE tech folder, which is excellent and this is not intended to in any way take away from that, but there are a few tips I think I can add.

I bought the Ford aluminum cover, which is a great value at less than $50. Ford uses it on their '08 and above diesel SRW trucks, so if they think it is worth doing then so do I. It looks nice, and fits perfectly.

The cover does not come with bolts, and the original bolts are not long enough for the aluminum cover. You will need 5/16-18 x 1-1/4" long stainless steel bolts. I used hex head, you can use allen cap if you prefer. Quantity is 12, and add lock washers too. A good hardware store will have those for less than $10.

First tip, loosen your fill plug before you remove the cover. You don't want to get everything else done, and then find your plug is wallowed out. If it is it will be a problem either way, but I would want to know before I got started. The plug just uses a 3/8" square drive ratchet. Mine was in good shape. There is no drain plug on the Ford 10.50" diff. There is no fill plug in the aluminum cover.
http://www.billpounds.com/truck/rear...reardiff01.jpg

My OEM steel cover was pretty rusty, but it was structurally sound and would have cleaned up and painted fine. Note there are two metal tabs with info stamped on them. One has your ratio code, and the other has the gear oil specification. Don't loose them.
http://www.billpounds.com/truck/rear...reardiff02.jpg

I was pleased to find my gears in excellent condition, and there was no water or excess particles in my unit. This is nice to know, and the only way you know is to open it up and inspect. Note, I'm skipping the stuff that Guzzle does a great job of showing. Like removing the cover.
http://www.billpounds.com/truck/rear...reardiff03.jpg

In the bottom of the differential casting are two wells, which will not drain without some help. It's important to clean these out well. Not only will metal particles settle there, but if there is any water intrusion it will settle there as well. Reach in and scoop it all out, followed with towels to get it all cleaned out.
http://www.billpounds.com/truck/rear...reardiff04.jpg

Clean the sealing surface of all the old silicone sealant. Guzzle used emory cloth, but I prefer course Scotchbrite pads. I think it does a better job, and there is less chance of grains of sand getting where you don't want it. I used the red stainless steel pads, which are very abrasive. Next tip, chase the threads in the cast iron diff. They will be dirty and have old silicone. Since you are doing this on your own time, take a little extra time and clean the threads. You want at least 1" of good thread, but be careful not to cut the existing threads. Get it all spotless and clean all the oil off using solvent. Make sure the surface stays dry.
http://www.billpounds.com/truck/rear...reardiff05.jpg

Next tip. A couple of studs in the threads will help align the cover without smearing the silicone around while you fumble with it. A couple of set screws would be best, but I didn't have any so I cut the heads off of a couple of long bolts. Select the two holes where the metal tabs will be replaced.
http://www.billpounds.com/truck/rear...reardiff06.jpg

Here is the aluminum cover, and the gear lube I selected. This Mobil 1 full synthetic has the friction modifier in it already for the limited slip.
http://www.billpounds.com/truck/rear...reardiff07.jpg

Here is the RTV silicone I chose to use.
http://www.billpounds.com/truck/rear...reardiff08.jpg

Here is the silicone applied, and this brings up a point where I disagree with Guzzles writeup. I applied the silicone and immediately installed the cover on the differential. I don't know where the "let it skin over" thing came from, but I see it repeated often. I think that is a mistake. I want this cover glued in place and there is no point in letting the sealant partially cure before placement. I'm sure Ford doesn't do that. And I might add that the Permatex instructions don't say that either. So, suit yourself on that, but I've given my opinion. If it leaks, well we know who will be redoing it. I'm certain that it won't.
http://www.billpounds.com/truck/rear...reardiff09.jpg

Here I have inserted all the bolts hand tight, except for the two studs. Next I just removed the studs with pliers, and inserted those bolts with the stamped metal tags under the heads.
http://www.billpounds.com/truck/rear...reardiff10.jpg


http://www.billpounds.com/truck/rear...reardiff11.jpg

Here it is all torqued down and finished except for filling with gear oil. Let the cover sit a couple of hours before you fill with oil to let the sealant get a good start on curing.
http://www.billpounds.com/truck/rear...reardiff12.jpg

All that's left is to evaluate the Mobil 1 friction modifier. I drove around in a few circles, first one way, then the other, to try to distribute the new oil into the clutch packs. I don't know how much if anything that did. Time will tell, and if I get any clunking I can add some friction modifier later.

Nice job, Bill. Great info and pics!

Bill, great write up, lots of good details and pictures are excellent..

Nice job on the write up. Does anyone know if that dif cover will fit a 04, 5.4 with a 3.73 rearend? If it will does anyone have the part number? I've wire wheeled and painted mine but the salt in Michigan will take its toll.

I never let it "skin over" either and have done a diff a LOT of times. I think I understand why they say it, but I don't think it works any better. Some diffs have a gasket and you could consider that dry, so I think that's sort of where it comes from. But, when making your own gasket I think it's best to follow the "Permatex" directions. It's worked for me a dozen times or more with no hint of a leak.

I think all of the 99+ f250 and SRW f350's use the same rear end.

yup :-bigparty

Great write up, tips, and pics :-X22

Those are some good lookin' shocks too!

I'll try & remember to rep ya after spreadin it around some more.

All the single rear wheel Superduties use the same differential, up to at least 2010. You can find the part number for the aluminum cover here:

www.partsguyed.com

They are an FTE sponsor too.

Part number is 8C3Z4033A

Got him for you Jason.

Excellent job with the write-up and pics Bill! Thanks for posting it.

Any mods that see this.....I'm thinking maybe a sticky in the tech folder would be a great idea.

Those teeth couldn't mesh any better. Nice cover but I wish you would have shown how you filled it, I don't have a suction gun. I think Guzzle "squished too much out" and came up with the " let it skin over" theory but I don't use it either and I'm sure Ford is not going to look out the window while it "skins over" either. ;).....nice pics.

nice write up, that cover does wonders for reducing the temps. I too agree, you don't need to let the sealant "skin over" Other than that there is nothing I would have done differently.

I should have, but it was a couple hours later and I had put the camera away. But it wasn't any problem.

The gear oil bottles have a nozzle built into them, and you can just stick it in the hole and squeeze out all but about 1/4 of each bottle. Then I used a piece of 1/2" nylon polyflow tubing about a foot long, stuck it on the bottle nozzle, the other end in the hole, and squeezed the last little bit. That overfills it a little bit, so you just wait for it to drain back until level.

I don't think I needed the tubing though. I could have emptied the last bit of all the bottles into one, and just stuck the nozzle in the hole.

Either way, there is lots of room under there and it is not a problem.

Thanks for all the kind comments.

Thank you for that part number.

Excellent write-up w/ pics... REP's given! :-drink