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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?
 

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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


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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
 

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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).]
 

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Discussion Starter #5
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!
 

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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).
 

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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.
 

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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!
 
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