12-bolt Chevy Upper Control
Arm controversy
There's been numerous discussions of a "special"
upper control arm for the GM A-body 12-bolt rear end. Here's some
pics that show the difference, and that it's not that big of a deal if you
had to adapt a "standard" arm to the driver's side upper bushing of
a 12 bolt rear.
Click the images for larger versions
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Arm on top is a stock 1971 Olds upper rear control
arm. The lower arm (black) is from a (supposed) 1969 Chevelle SS
that had a 12-bolt rear. As you can see, the SS arm is notched and
reinforced below the bolt hole.
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Closeup detail of the 12-bolt upper arm. There's
a reinforcement plate spot welded over the hole from the factory.
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12-bolt upper arm on a 12-bolt rear. Not shown
is that the passenger arm is the same for all rears, no clearance problems.
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Non-12-bolt arm on the 12-bolt rear. Note
the interference with the carrier housing. This could be fixed with
a grinder in about 30 seconds.
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Just a comparison of the new 12-bolt rear with the
stock 10-bolt BOP rear. The BOP rear did not appreciate being
behind a 403 Olds with a 700R4's low 1st gear.
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This is a set of F41 suspension braces. They
go from the upper to lower control arm mounting points.
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Thanks Ebay for a great
deal on both items. The arms were only $20 because they were dirty
(ebay bidders hate to clean parts), and the rear was ~$150 because the guy
had it listed wrong and wouldn't ship it. I bought the
F41 braces for ~$45 as shown, easier to pay $45 for bolt-on's instead of
$40 and I have to clean and paint....
If you're doing a A-body rear end, get a set of the F41 reinforcement bars
and use Poly bushings. Just grease well and they'll be no squeaks
- these cars handle *and ride* much better once the ass end isn't sliding
around like a Armor-All'd bench seat.
Soon to follow, front big disc brake conversion done the right way.
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More useless facts from
the degenerates at grimers.com
Don't belive the hype, take hold of the pipe!
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