12 bolt Axl questions

I have a 3.73 truck 12 bolt with an Eaton "HD" posi that was in $500 area 15 years ago it was run low on gear oil and the spider gears gauled and cannot remove cross pin with out cutting it, a pin spider kit for it is $250! Is that aftermarket Eaton posi unit the same as the old oem eaton posi units, I've seen spider/pin kits for OEM 12 bolt posis for less than $100 are they interchangable or am I stuck paying top dollar for specific parts for my Eaton. I've tossed the idea of replacing the whole works carrier gears ect but it's to expensive at moment at moment it's patch up the 12 bolt or run the 3.08 10 bolt which sucks the life out of my performance from my big cam open intake 2500 stall setup. Any imput would help thanks

Keep the 12B!
I`ve been messing with 10 & 12 bolt Eaton LSD`s for (*cough*) a l-o-n-g time & I`ve never heard of an `HD` 12B Eaton. Not saying they don`t exist, just not aware.
My `70 BBC Nova SS has a factory 12B, & if any vehicle needs an HD unit, that one sure does.
Because I spent a bunch of time & effort dialing it in on the stiffness of it`s operation, whenever I needed parts, (spiders, clutches, springs & plates) I just bought parts for an Eaton 12 bolt Limited-Slip carrier. Never designated whether it was an `HD`or not. None of the parts guys ever asked for that clarification.
Could be that the carrier in there now has the stiffest springs (IIRC, there`s 3 variants. They`re ID`d by color) & a Severe-duty clutch pack. Clutch packs are available in different materials & disc counts, which effects how stiff the unit runs.

I`d measure the O.D. + the length of that center pin. More than likely, it`s the same as the OEM. Which would also allow for the use of an OEM set of spiders.

Ahhh I dunno my uncle initially purchased the unit before I bought that truck off him he said that's what it was called, I just did some looking to see if there was a HD designation and I didn't see one either BUT I did see a bunch of descriptions saying HD posi unit so I'm assuming he thought it was the model vs it just being a sales pitch description. I didn't assume it was a special version I just figured it was what Eaton called it. But I'll check the dimensions and take a look see,wasn't even tho GM used them for OEM I wasn't sure if new ones bought from Eaton were the same or just similar units

As far as I know and I could be wrong. But I am pretty sure that the oem Eaton or a aftermarket one are the same.

They've changed very little over the years. Mostly with the replaceable internals. Carbon Fiber clutches were myths back when I last had a 12B apart.
3.73's. Mmmm...
3.08's. Ewww!

A 12 bolt in a GMT400?

Acw73 said:

Ahhh I dunno my uncle initially purchased the unit before I bought that truck off him he said that's what it was called, I just did some looking to see if there was a HD designation and I didn't see one either BUT I did see a bunch of descriptions saying HD posi unit so I'm assuming he thought it was the model vs it just being a sales pitch description. I didn't assume it was a special version I just figured it was what Eaton called it. But I'll check the dimensions and take a look see,wasn't even tho GM used them for OEM I wasn't sure if new ones bought from Eaton were the same or just similar units

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Could be that the unit has the stiffest springs installed. That'll make the inside tire bark/chirp/shudder around tight corners, say in a parking lot or when making slow left/right turns at intersections. "Heavy Duty"

Acw73 said:

I have a 3.73 truck 12 bolt with an Eaton "HD" posi that was in $500 area 15 years ago it was run low on gear oil and the spider gears gauled and cannot remove cross pin with out cutting it, a pin spider kit for it is $250! Is that aftermarket Eaton posi unit the same as the old oem eaton posi units, I've seen spider/pin kits for OEM 12 bolt posis for less than $100 are they interchangable or am I stuck paying top dollar for specific parts for my Eaton. I've tossed the idea of replacing the whole works carrier gears ect but it's to expensive at moment at moment it's patch up the 12 bolt or run the 3.08 10 bolt which sucks the life out of my performance from my big cam open intake 2500 stall setup. Any imput would help thanks

Click to expand...

Supercharged111 said:

A 12 bolt in a GMT400?

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Could be swapped. The year wasn't mentioned. Square body?
Need pix. Truck & the diff.

I found identification numbers it's EDL-32840, my research is that it is an Eaton 12 bolt truck 4 series posi, nothing special or out of the ordinary just run of the mill Eaton brand posi unit, it currently has 3.73 gears. Like I thought the "HD" thing was just what I was told to me by my uncle when he bought it and again when I bought the truck off him. He had trashed the original 3.42 10 bolt and found this open 12 bolt and had a shop change out the spring perches to put it in that 88 silverado. If GM parts are interchangeable that would be good Eaton genuine spiders and pin are expensive to point a new carrier would be only little bit more money. The spiders spin on the pin but gauled to the point I tried removing the pin and it will not budge (and yes the lock bolt/pin is out) I'm thinking gonna have to cut the pin somehow I'm afraid if I press it out it will damage the holes in the pin holes in the carrier, and advise on removing that hard as hell center pin? Would a carbide grit sawzallot blade cut it? A regular bi-metal won't even scratch it...

I had an identical open Axl same gears n all except 6 lug in my 82 k1500 I swapped into it, it was the original Axl I removed from a 74 4wd k5 blazer, so I'd say my current one was from that era. Aside from being a stronger Axl over the original 10 bolt I like having a 12 bolt in my 92 Cheyenne because it just looks alittle more serious.