Rear differential help

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Mar 7, 2017 | 07:48 AM

Taylor Doyle

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Rear differential help

OK, looking to the gods for help again. Trying to figure out what rear end I have on my 79 f150 custom 302 long bed, no tag can be found on the rear end...found #''s stamped as follows: D2SWZ668C also 6523 SF2, 6J8, and an upside down 25? It has 10 bolts around the outside.. trying to figure out what fluid to use to replace the old. Need your help thanks!

Mar 7, 2017 | 08:56 AM

Rollingscrapmetal

Tuned

Joined: Jul 2016

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Are the bolts to the front or rear of the vehicle

the 9 inch has a third member so their bolts face to the front the Dana 44 doesn't have a third member but it has a differential cover so bolts face to the rear

Mar 7, 2017 | 09:22 AM

78 PEB

Cargo Master

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From: Ideeho

Should be a 9" but pics would help identify it

Mar 7, 2017 | 09:40 AM

351Cleveland C4

Lead Driver

Joined: Jul 2011

Posts: 8,678

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From: On the Edge of the Desert

Gear oil. You use gear oil.....

I recommend regular 85-140

As far as the axle, it's Most likely a 9" with 3.00-3.25 gears. Not that it matters for what you need to know...

Mar 7, 2017 | 09:54 AM

Taylor Doyle

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Quote:

Originally Posted by 78 PEB

Should be a 9" but pics would help identify it

Mar 7, 2017 | 09:59 AM

good to doo

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From: british columbia, canada

That's a 9"

Mar 7, 2017 | 09:59 AM

78 PEB

Cargo Master

Joined: Oct 2010

Posts: 2,674

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From: Ideeho

That's a 9".......and as 351 Cleveland C4 said above......gear oil....I prefer 85W140.......

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Mar 7, 2017 | 10:07 AM

Ozzie H.

Laughing Gas

Joined: Nov 2013

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From: S.E. Louisiana;so far USA

Quote:

Originally Posted by Taylor Doyle

I can't provide any definitive answer. The Ford truck shop manuals have a lot of ID information in them (but I don't have the ones from '79). I'm guessing a bit, but it sounds like it "might" be a Ford axle with a 9" ring gear. The one in my '76 F-250 has a tag attached between two of the cover bolts on the driver's side, but it is a Dana.

The ratio there is 3.07:1.
If you're wondering about ratio, the surefire way is to remove the cover and count teeth (in case you're not the original owner).

As far as the lubricant goes, in '76, it was hypod gear lubricant with Ford part number C6AZ-19580-B or equivalent meeting Ford specification ESW-M2C105-A for a non-limited slip differential. For the "Traction-Lok" axles, the numbers changed to C9AZ-19580-A and ESW-M2C119-A. To tie it down a bit better for '79 you could look in a '79 Ford truck shop manual (vol.5?) or search the technical information portion of this forum.