Ok, I need another opinion. I am restoring my 70 SS 396. I have the buildsheet and the car was built at the Lakewood Plant. My buildsheet is posted on www.chevellestuff.com (http://www.chevellestuff.com) under the buildsheets for reference(mine is the one delivered to Dan Vaden Chevrolet in Savannah, GA)(Vehicle ID: 133850). After checking the number on the axle tube on the rear end in the car I discovered the code: CW 1026 B and is definitely not a posi rear. My car has, according to the buildsheet, the G94: 331 ratio axle and G80: Positraction. The code I found on the rear end conflicts with the code "CF" found in box 29 of the buildsheet. I compared to a few other buildsheets referenced on the site and found a few to have "CW" in box 29 and were not listed as having the G80-positraction option. My question is, first off, is it possible that the plant put the wrong rear end in the car according to the build sheet. Also, having a "CW" coded rear, are there any "CW" rears out there that came from the factory with posi or was this for limited slip only. If someone has any insight, I would appreciate it. I know the possibility is that the rear end was swapped out long ago as well.

A CF is a Posi.
A CW is Not A Posi.
You are showing an assembly date on your rearend of Oct. 26.How is this compared to your cars built date?
I am guesssing,based on what you have provided,it is not the Differential housing your car was born with.
It is not uncommon for people to switch rears,as I doubt the factory did it.

Dennis,

After I decoded my rear axle housing, it turned out to be date correct for my car but decoded to an open rear. One thing that supprised me when I took the rear inspection cover off was that indeed was a posi rear. As funny and weird as it may sound, my car has a dealer installed optional towing package. Tow bar, heavy duty electrical system, and posi unit. This was told to us by the previous owner who was the second owner. He got this from the original owner who had that installed because he towed around a small trailer for camping. Again, yours is probably different sinario cause you have your build sheet that says one thing with a case that says another. Like was said before, best bet would be to see the casting or manufacture date and compare it to the rest of your cars dates to see if it would be original. graemlins/thumbsup.gif

Brian & Rick,

Thank you both for your replies. After I posted this I had looked around on the Chevellestuff.com website and found a breakdown of rear end codes. On the axle tube I had CW 1026B, the only year that fit was 1968. In 1969 & 1970 it would read CCW. So, unfortunately it looks like the rearend was swapped out to a 1968 331 open unit. I will verify this when I pull it out. My car's assembly date was Feb. 19, 1970 and October would appear to be a little early based upon the other dates I have found on the car(most December, January & February) Rick, your L-78 is B-E-A-Utiful! One question, I have seen the master cylinder on these cars painted black or left natural(cast). Which is correct? I was leaning to the natural look that your car exhibits. Was it dependent upon where the car was built? This old(1992) restoration guide I have says it should be painted black, but again, this book had a picture of a 1970 SS with a 4-spoke 442 wheel representing it as original... Brian, I'd love to see pics of your Elky. Thanks again guys

Dennis
The Master Cylinder was possible with either finish.Although Black seems to be the most commonly restored shade.

Dennis, I have a similar situation. My build sheet calls for 3.31 posi, but my axle tube stamping decodes as a 2:73 open. I know that my car was drag raced years ago, so the original rear was probably ruined. At some point my car was put back on the street and a different 12 bolt was put back in. Luckily the casting date on the housing is correct for my car. Yours was probably switched out under similar circumstances or maybe the car was stolen and recovered at some time. My point is that after 33 years anything is possible.

Hi Tim,
Yep, you are right about that. I am in touch with the second owner that had the car from 1978-1993. Before he got it the original owner blew the engine so must have done the same to the rear. Like your pictures especially "Raped Rat". Chassis looks great! Thanks for the reply

Thanks for the kind words Dennis.