Is it true that '70-'72 4dr chevelles often came with 12 bolts and more often than not, they were posi? I know that many (almost all) of the '71-'72 4dr chevelles had disk brakes and many of them had air conditioning and tilt wheel! I have seen many '70 chevelles with drum brakes, but '71 and '72 have always had disks from what I have seen (on 4drs that is!) I have never thought to look at the rear end in these cars, but tonight a very good and experienced source told me that most 4 drs came with 12 bolts and many of them are posi's! Does anyone else have similar info?

Well I have a 1970 Sport Sedan, and let me tell you: There is no 12 Bolt Posi hiding under there, no tilt wheel... but a nice overpowerful AC unit to match the 4 wheel drums http://www.chevelles.com/forum/frown.gif

------------------
Francis Taracido
Sniper0666@aol.com
Proud Patron of Quadzilla

That information has got to be incorrect. While I am sure the 12 bolt and tilt wheel were available on the 4 door models, the majority of them had 10 bolts and the regular steering column. I have had 4 of the 4 door cars, all of which I used for parts, and none of them had the tilt or the 12 bolt and only 2 had the disc brakes and 2 had ac..........GT

You could have ordered a car with this equipment but it was never standard. The 12 bolt was referred to as the HD rear axle in the Chevy literture. Chevy would install a HD axle in a car that required it like maybe a fleet car i.e. Police, Taxi with servere service. A junk yard owner told me years ago to look at the sta-wgns, lots of times these were used for trailer towing and had 12 bolts and posi. sounded reasonable, still looking but never found any yet.

[This message has been edited by elcamino (edited 05-13-99).]

elcamino, that information about the chevelle station wagons that the junk yard dealer told you is exactly what my source told me and he said that it applied to 4 drs also, especially '71-72. He also told me that most '71-72 4 dr chevelles had discs because of a new emphasis on safety that occured in '71? With 4 dr cars being so much heavier and usually used by families, safety would be a factor on these cars. I don't know how much of this is true, but some of you already say that it isn't, so this guy might just be talking from his own exposure and experiences. I know that I just took a tilt steering and some disk brake parts off of a '71 4 dr hardtop and it also had a/c, but I didn't check the rear end. I am going back next week to check it, just in case.... That really would be something to find a 12 bolt (HD option) posi under that abandoned 4 dr! Thanks for the replies!

Generally it's the engine that determines whether you get a 10 or 12-bolt. The 350-4 in '70 got the 12-bolt, the 350-2 got the 10. Sometimes the engine/tranny pairing determines i.e. in '67 the L30 327/275 used a 10-bolt, but the 4-speed version got a 12-bolt. In the B-body line (Biscayne-Caprice) the wagons got 12-bolts on all V8s. A friends father had a '67 Biscayne sedan with a straight six and a 12-bolt dual upper control arm 3.31:1 posi. It also carried a front sway bar & hd. suspension, which tipped us onto the Z04 h.d. chassis equipment (police/taxi).

Disc brakes became more popular after people realized how inadaquate the drums had become, given the speed potential of many machines. A lot of people passed on the disc brakes to buy vinyl roofs. Chevy put discs on all SS starting in '69 (except '73-4 Nova SS) as standard. To a lot of people that passed on discs said 'next time', and so the uncommon discs of '68 became the much more common braking system in the '70's.

You find 'em wierd places sometimes. Years ago, after looking seemingly forever in the 'yards, we finally found a 3.31 12-bolt posi, in a 69 6-cylinder Chevelle wagon!