I have a 72 Skylark/GS 455 clone that currently has a 2.56 open 8.5" 10 bolt rear, casting number 1235197. I was told it's a 2.56 by a mechanic, and I just found the LK stamp on the axle housing. With the 455, I just spin one tire in 1st gear if I nail it, so I'd like to get a positraction carrier put in. I'd like to keep the gears numerically lower than a 3.23, and would be perfectly fine with keeping the 2.56 gears if I can. Depending on what I've read, some places have said that the 2.56 gears go in a 2-series carrier and the 2.73 or numerically higher gears go in a 3-series carrier. However, other places seem to indicate that they're all the same carrier. I've also checked the Eaton website, and they have a posi carrier listed for 1971-1989 GM 10 bolt 8.5" rears for 2.73 gears and higher. So, the question is: what is the easiest way for me to add a posi carrier to my setup? Will I need to find a new (to me) 3-series carrier and get 2.73+ gears? Will I just need to get a 2.73+ gearset and the posi unit and put it in my current carrier? Or, can I just put a posi unit in using my current gears and carrier? Thanks in advance for any help you all can give.
The carrier is either posi or non posi. If you add an Eaton Posi, that is the carrier you are buying. You may be able to use your 2.56 gears with the 2.73 and up carrier with a spacer, not sure. You can also add a Power Trax unit like this one to your current carrier. http://www.summitracing.com/parts/pwt-1920-lr/overview/
Contact Monza on the board, he set me up with a GM refurbished 2 series posi for my 2.56, a fair price to boot. You can put a 3 series gear on a 2 series carrier if you add a ring gear spacer. sometimes I wish I had a 3.08 gear for better acceleration, but the 2.56 is sure nice @ 80mph on the freeway
That would be Monzaz, http://www.v8buick.com/member.php?3880-monzaz This is his website, www.jdrace.com
I did contact Monzaz a year ago or so. My mechanic (I'm starting to move on to a different one) mis-identified my rear as an 8.2" rear, so what I was looking for was more difficult in my mind. He asked me to identify my rear and take pictures, but I just never got around to it, as more urgent car issues needed attending to. A 3.08 still wouldn't be too bad at 80. Instead of 2,500, you'd be turning around 3,000. With the 2.56, even 2nd gear doesn't go to redline before I've crested 80 mph lol.
Thanks for the explanation. For some reason, I thought the carrier was the case that had the casting number on it. I just had my terminology wrong, and now it makes perfect sense. If I need to buy new gears, I might go for a 3.08, or maybe Monzaz will have a 2-series lying around. I'll contact him and see. Whatever he has, it probably won't be more expensive than buying a brand new Eaton unit lol.
The 2-series posi units can be found a little cheaper than the 3-series. You want to look for casting #410409N. These will also have large 6's. On the side opposite the ring gear. The other casting # to look for is 726. If you don't find something,let me know.
There are no NEW 2 series posi units for 8.5 or 8.2 or 12 bolt chevy in the aftermarket. They will all be reconditioned GM units or used. Jim J D
I used a PowerTrax on my 2.56 and it has endured hundreds of quarter mile passes as well as street driving. It does make a lot of clicking sound....sounds like something is broken or breaking but that's just the way they are unless they have changed something on newer ones.
HUMM... Should not sound like it is breaking...JUST clicking. Check you install you may have the wrong amount of distance in the center. .130 -.154 is all it can be. no thinner, no wider
