I was told that this is a posi rear, looks like an open to me? Please help.
Thanks. axel numbers are BM 0905 G2

http://home.comcast.net/~stevetia1/12Bolt.JPG

My first guess is an open diff. Typically, you'd see 4 springs on an Eaton posi. There is a way to shim the spyder gears to eliminate the springs, but that's a racing thing and fairly rare.

http://www.justrearends.com/images/Products/5d9c08fb-e75c-4b34-833b-ff6d2ef1ad1fetn-19554-010_w.jpg

The axle may be coded for a posi carrier .
http://www.camaros.net/years/67/67rearcodes.html

Actually it is a posi. That is an Eaton posi with the preload springs and plates left out. Look at the picture close and you will see the wear plate that goes over the tabs on the clutches. You will also see the large ballance weight next to the hole in the case. You will also notice that one of the pinion gears is missing. This posi has the old type gears in it, so you will have to find a used replacement gear to go in it. The new gears are made different and must be installed in a set of 4. The preload springs and plates are available in 3 different preload amounts. There are the standard 200 pound springs, 400 pound springs and 800 pound springs. I have the 200 and 400 pound sets on the shelf.

Looks like a pretty good contact pattern on the ring & pinion gears.

Freddie you are the man.:thumbsup:

Wow, I didn't even notice the missing gear. I might have extra gears if BGH don't.

I don't think I have one of those. I'd say that it probably broke because the cross shaft is new. Better check the other gears for broke or chipped teeth.

Thanks for all of the help. I didn't know if it was a posi without the springs and plate. I did get a set of new spyder gears, springs, plates and axels with it. thanks for all of the help. I am new to this site, nice to see the great knowledge base.

Do I need to have a professional put in the new spyder gears, springs, plates, and axels? Or is this something I can do? Never worked on a rear end before.

thanks.

You may want to take to a pro ?

I do have a trick to the springs and plates. I mock them up, press together in a vice,then use some heavy cable ties through the springs and plates. Install and cut the ties... USE CAUTION (it took me a few times to get right... only done one time before)

Which springs do you have? The 200 pound springs are green and the 400 pound springs are yellow. 400 is harder to install than 200, and 800 (red) is a real pain. I recommend setting the preload on the clutches before installing the springs. This is done with shims behind the clutch packs. You could just install them the way they are. Check the clutches for wear. It is possible that they need to be replaced.

If you are interested I build these. You can send me the posi and I will assemble it for you.

Here is the set the rear end came with. No color on the springs. The rear did not come with backing plates. Looks like they are the same ones that are on my 10 bolt?

thanks again.

http://home.comcast.net/~stevetia1/12Bolt2.JPG

Those look like the 200 pound springs. It also looks like you have a set of the older gears. There should be 18 teeth on the axle gears and 10 on the pinion gears. The new gears have 17 teeth on the axle gears.

The brake backing plates are the same on the 10 and 12 bolt.