[SSedan64]

What type 8.5" Posi is this? Auburn? Eaton?

[ericnova72]

Do you have any more views of it?? Can't tell for sure from this angle but doesn't look like an Eaton to me, looks more like an Auburn.

[SSedan64]

No mo Pics, it's for sale on another forum. I asked the seller a few days ago but He hasn't answered. Looks more like an Auburn to me also.

[cobalt327]

Looks like an Eaton to me. No? Maybe a cone type Auburn? Just used to seeing yellow springs and a bigger scallop cut out of the spring plate if it's an Auburn.

Prolly why I don't make a living at this.


That is one HIGH gear!


EATON DIFF (got yellow springs! lol)


AUBURN DIFF

[SSedan64]

That's what I thought, seller said 3.42 gears Pinion looks like 15th, if Ring is 41th = 2.73

[SSedan64]

I was wrong, Ad didn't say 3.42.
Don't the 8.5" Carriers fit all gear ratios?

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This is a ?? about a different 8.5" from above one.
Does a small amount of pitting on Spider gears weaken them enough to matter?

[big gear head]

That's an early Auburn with the bolt together case. Keep in mind that these are not rebuildable. The 8.5 uses the 3 series for 2.73 to 5.13 and a 2 series for 2.56 and 2.43 gears.

[cobalt327]

big gear head, what was the bolted together diff used in? What years? Thanks in advance.

[big gear head]

I've only seen them in early '70s Camaros. Most of the 8.5 rear ends got the Traction Lock.

[SSedan64]

Originally Posted by big gear head

That's an early Auburn with the bolt together case. Keep in mind that these are not rebuildable. The 8.5 uses the 3 series for 2.73 to 5.13 and a 2 series for 2.56 and 2.43 gears.

Thanks BGH,
I don't want an Auburn, I looked through your Diff Pics but didn't see one like it.
There's a 8.5" Traction Lock w/3.42 gears for sale also. Seller said, "out of a rear with about 50k on it. gears look great. the spider gears have a small amout of pitting on them. other than that its a great diff. clutches are nice and tight".

Does a small amount of pitting on Spider gears weaken them enough to matter?

[cobalt327]

I'd be cautious of "pitting". If it's actually the surface flaking and not slight pitting from rust, I'd be worried that a failure was around the corner.

I have personally seen this on a 12-bolt A-body car peg leg diff that had too many burnouts on it. I suppose the same thing could happen to a LSD if the tires were different diameters or if there was a lot of excessive tire spin on one side or if the posi was weak.

I suppose you could replace them, to be on the safe side, along w/the shaft. And the bearings if you are a worrying type (like me).

Hopefully BGH will have a brighter forecast for you.

OT- BGH, I appreciate your info here as I'm sure many also are. Why don't you put in for moderator? More HERE.

[SSedan64]

Most likely from rust while sitting, people hoard those 8.5" rears.
In another thread BGH said those Spider kits are about impossible to find, the good GM gears anyway and very pricey.

[cobalt327]

Originally Posted by SSedan64

Most likely from rust while sitting, people hoard those 8.5" rears.
In another thread BGH said those Spider kits are about impossible to find, the good GM gears anyway and very pricey.

Bummer. I suppose a matched set from a good diff could be used, but hopefully it's just minor rust pitting like you say and not a loss of the hardening.

I think of all the diffs I just tossed back when. But they'd have been sitting for YEARS and might have the same rust you are seeing! Oh well...

[big gear head]

If the surface is flaking then the gears are starting to come apart. They might last a lont time like that, but who knows. None of the parts are available for the 8.5 Traction Lock now except the cross shaft and the retaining bolt, so good used parts are all that's left. There are a lot of 2 series Traction Locks out there that can be had cheaper than the 3 series. All of the internal parts from the 2 series will swap into the 3 series. I'm getting a 3 series in a week or two and I'm going to see if I can do some parts swapping with some other differentials and find something that will work.