I am getting ready to have a 12 bolt set up for my 67. I have a factory 69 12 bolt with 2.73 eaton posi. I also have GM 3.31 gears that I would like to use. After researching it appears I will have to use a complete different posi unit for 3.31 gears is this correct? What are some affordable units?

My car is currently a 400 hp 396 with a th400 and 2200 stall and a peg leg 10 bolt 3.08 rear.

Will 2.73 gears make my car a complete dog? and burn up my trans with the stall?

thanks

I recommend changing the gears. The 2.73 will probably cause the converter to build up a lot of heat. You will need to swap your 2 series posi for a 3 series. Look for one with the casting number EDB30140.

Another option is to use a ring gear spacer with your existing posi carrier.I have used them many times on some high HP cars without any issues.Last one i bought was around $30.00 and are available from Jegs, Summit.

Here is what a ring gear spacer can do for you. I've seen this several times.
http://thumb7.webshots.net/t/14/15/8/46/32/2501846320041712107dAvBiX_th.jpg (http://rides.webshots.com/photo/2501846320041712107dAvBiX)

Both of the replies above are good info.
A 3.31 gear will not work on a 2-series carrier as is. You CAN use a ring gear spacer to adapt a 3-series ring gear on a 2-series posi unit.
OK, so if you can use a spacer, why would Freddie (BGH) say that you need to switch to a 3-series posi unit? Because, that would be the preferred way to go, simple. And, I whole heartedly agree with Freddie if your car is going to be subjected to regular heavy duty abuse. But otherwise, if your car is going to be primarily a street/driver/performance car, then you should be fine with a spacer. When installing a spacer to adapt a 3-series ring gear to a 2-series posi (or adapting a 4-series gear to a 3-series posi), longer bolts are required and some people strongly feel that just increases the possibility of the bolts to sheer under extreme torque loads. Maybe so, maybe no, but with a 12bolt ring gear in a car that is primarily a driver, I'd go with the spacer. If you don't feel comfortable with that, then certainly don't hesitate to buy a 3-series posi unit and put the 2-series on Ebay, or, email me about it (I could use one).

FWIW in the early 70's I used a spacer for 4.10 gears on a 3 series carrier in a 12 sec 396 Nova with slicks and had no problem. May have been on thin ice but it worked for me.

By the way, a slight deviation from the original issue (but still Chevy rearends).
By any chance, does anyone just happen to have any JUNK 55-64 rears? I need a pair of the spanner nuts (adjusting nuts) for the carrier bearings (and the little locking tabs). At one time, these rears were a dime a dozen in junk yards, but they're getting kind of scarce now.

I apologies to Roger. I seem to be in a rude mood today. One of the guys that I work with just jumped me for being rude to him. I just don't like spacers. I've seen too many problems with them.

I apologies to Roger. I seem to be in a rude mood today. One of the guys that I work with just jumped me for being rude to him. I just don't like spacers. I've seen too many problems with them.

And I completely agree with Freddie's viewpoint about using (or not using) spacers to adapt a ring gear to a different series posi unit.
Freddie does a WHOLE LOT more rears thatn I do, and thus, he probably has seen a lot more broken parts than I have seen. BUT, I have rolled the dice a few times and built rears with a spacer plate (and I may pay the price for it some day :().
Also, the BULK of my rearend rebuilding expertise is with the earlier 55-64 type rears.

If you can find a 3 series Eaton case you can transfer all of the internal parts from your 2 series posi into the 3 series case. Sometimes you can find a 3 series with broken gears for cheap.

I apologies to Roger. I seem to be in a rude mood today. One of the guys that I work with just jumped me for being rude to him. I just don't like spacers. I've seen too many problems with them.

No apology needed. I agree 100% that in a perfect world where money is no object (which unfortunately i do not live in:D) buying a 3 series carrier is the best option. I have used ring gear spacers on my 4 speed cars with slicks before and broke multiple sets of spider gears yet never broke ring gear bolts due to a spacer. I think it is a viable option to spending $400 or so on a new posi unit.

Thanks for the input. I will probably not be real nice to the rear so I think I will opt for a 3 series carrier. Now I need to view my options for a new carrier, used or shopping the whole rear and getting one closer to my needs.
thanks

If you want a price on a Moser unit send me an email. I'll do the best I can to get you exactly what you need.

Dont forget you can also buy a thicker gear for the different carrier. Just another option for some guys.

Dont forget you can also buy a thicker gear for the different carrier. Just another option for some guys.
I was just about to suggest this same thing.

With the 12 bolt that only works if you have a 3 series and you want to install a 4.10, 4.56 or 4.88.