My rear differential service - with pics

[TexasRebel]

Checking and changing the lash can be detrimental checking isn't going to hurt anything, but can be an alert to problems to come...

[EXv10]

Not really.

[wallz]

Nice write up.

When I did mine, I also found that jacking up under the back receiver hitch also gave me some more room under there especially when refilling. It made it easier to lift the bottles up to empty.

[Krewat]

Originally Posted by EXv10

Checking and changing the lash can be detrimental. The lash can vary with the gearset due to the original cutting of the teeth. What is more important is the contact area which can be checked with red lead, prussian blue, etc. Basically if it doesn't whine, don't touch it.

I can't agree MORE! Check the pattern. I almost always do it when I have the cover off of any diff.

If the pattern is perfect, leave it alone. Don't even check the backlash

If you checked it and changed it, not only is it a lot of work (pressing off and on the bearings), but you will change the point at where the gears meet, and you will either CREATE a whine, or worse if you're towing or hauling heavy, overheat the gear lube because of the resulting small contact pattern until they are broken in again.

[TexasRebel]

eh, I'd have to know...

and i brought it up because of the close up of the ring gear... First thing I saw were the lines on the teeth... probably just an illusion, though. Then again... you're talking to a guy who doesn't have "good enough" in his vocabulary...

[EXv10]

I'm pretty sure those lines are from the original cutting of the gear and the wear hasn't gone deep enough to eliminate them. Those teeth are actually meshing very well, the pattern covers a large swath and terminates perfectly at the toe and heel of the tooth. Teeth that aren't hitting right will have shiny areas with on obviously irregular pattern.

[figurhead]

Bill/bpounds, great writeup. I found a nice set of Mag Hytec covers (trans & Rear Diff) on Craigslist for $150. I didn't document the isntall quite like you have. I should've tho. They (Mag's) are so nice with the gasket, no silicone required, a nice o-ringed fill hex bolt, nice allen bolts for bolting it on, and places for temperature gauges, dual magnetic pieces for grabbing anything in there, etc. No leaks after a month of driving, the o-ring gasket only.

The rearend looks great. I've always liked the polished look, but I have come to enjoy the black/polished look as of late. Take care.......

[flatbeder]

thanks bill great write up!...gonna do my diff when i get home its leaking like a siff...also gonna inspect the pinion seal and repair accordingly. probly gonna buy that fancy diff cover aswell!!!

[bpounds]

Originally Posted by TexasRebel

eh, I'd have to know...

and i brought it up because of the close up of the ring gear... First thing I saw were the lines on the teeth... probably just an illusion, though.

I'm not an expert, but I've seen plenty of gears in my time, and I can say that nothing there alarmed me. I was suprised how much detail the picture showed. I think the flash affected it a little. It definitely highlighted the contact patch much more than the naked eye.

I was looking for any evidence of a streaked path, like where a bit of grit might have scratched the surface. I ran my fingernail across a tooth feeling for any bite or grab of my nail. The 2 or 3 teeth I touched were smooth as glass.

[EXv10]

They are in real good shape.

[smlford]

Great write up and it sure looks good too.
I have to ask though... why did you (and others) do this?
Has anyone had problems with their diffs?
I've seen several write ups on this but no one said that they were having any problems...
Thanks

[bpounds]

Originally Posted by smlford

I have to ask though... why did you (and others) do this?
Has anyone had problems with their diffs?

No problems. It's always been quiet, and my limited slip seems to work, at least equal to my expectations.

I bought the truck with 30k on the clock. Therefore there were some unknowns. The rear looked so good, I don't think I am going to bother opening the front diff.

I tow frequently. And even if I wasn't, the Ford recommendation of 100k between diff service doesn't set well with me.

As for the aluminum cover, I would not open a diff just to install that thing. But since I was doing the service anyway, spending $50 on an aluminum cover was a no-brainer. I would have spent a couple of hours cleaning and painting the old steel one. I'm sure it cools the lube better too.

[Krewat]

Bill, at least pull the fill plug on the front and make sure there's no water in it

[mcrespousa]

Great write up. In the 1st picture with the cover off, inside the round cutout, does that look like a crack?

[98SurplusExpy]

Originally Posted by bpounds

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

How 'bout the P/N for the actual Ford bolts used on the '08-up ??

EDIT:
The P/N for the "Ford" bolts is 6L1Z-4346-AA ... and they aint cheap either ... 12 will cost more than the cover!

McMaster-Carr has a 5/16-18 x 1-1/4 Stainless Steel Serrated Flange Hex Bolts (#97646A160) for $10.02/pk (Sold in packs of 10) ... these are probably closer to the Ford bolts and you won't need to add a lock washer.

There's also a mention of a 5R3Z-7860108-AA "Plug" going on the cover; but, I don't see such in the OP's pics.