Author Topic: 12 bolt restoration  (Read 7993 times)

JohnSSL78

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12 bolt restoration
« on: December 28, 2005, 01:58:12 AM »
I am starting the restoration of my 69 12 bolt rearend and need advice on the painting of it. Did the factory completely assemble the rearends including all brake parts and then paint them? Were the bolts painted also? I assume the brake lines were put on later during the cars assembly?

John

william

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Re: 12 bolt restoration
« Reply #1 on: December 28, 2005, 04:23:15 PM »
I believe axle housings were painted [glossy black] immediately after machining. Assembly paint daubs were later applied on the axle paint. Since the axle paint wasn't very good it did not adhere for long particularly in rust belt states. Brake components and axle parts [flange, etc] should not be painted. The rear axle cover and backing plates were likely received already painted. In my opinion cast-blast is not correct for axle housings.

Another common error is cast-blast for rear brake drums. There are photos in several vintage magazines showing the installation of t-bars or gears; drums were semi-gloss black. 

JohnZ

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Re: 12 bolt restoration
« Reply #2 on: December 28, 2005, 04:27:27 PM »
The rear axle assembly (housing, tubes, diff, rear cover, backing plates and drums and parking brake cables) was painted at the axle plant as a completed assembly just before it was placed in the shpping rack; the brake pipes and center block were installed later at the car assembly plants.
'69 Z/28
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william

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Re: 12 bolt restoration
« Reply #3 on: December 28, 2005, 10:37:16 PM »
Parking brake cables are never painted.

KurtS

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Re: 12 bolt restoration
« Reply #4 on: December 29, 2005, 04:07:19 AM »
That was the one detail that I noticed too. The rest I agree with. ;)
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KevinW

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Re: 12 bolt restoration
« Reply #5 on: December 29, 2005, 02:11:47 PM »
But if the drums (and brake internals) were installed prior to painting, then the parking brake cables had to be installed and painted at the same time!  GM wouldnt have added them later.  Something is not adding up.  Either the rear was painted without the brake drum, cable and internals, then brakes were added later (unpainted) or it was all together including cables and the whole unit was painted.

Thoughts?

william

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Re: 12 bolt restoration
« Reply #6 on: December 29, 2005, 02:19:51 PM »
That is why I thought the housings were painted before assembly-brake parts are never painted. Also I did not think the fasteners retaining the cover and backing plates had paint on them either. But John Z was there.

There is a good photo of a '69 Z/28 axle in the March '69 Hot Rod. The photo shows the brake drum mostly painted around the circumference, not much on the front around the studs.

Another good photo in the Aug '69 Hi-Perf Cars of the #3 ZL1 axle. It appears to be glossy, pb cables not painted.

Another detail was a paper label on each brake drum with the axle code.

Buddy

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Re: 12 bolt restoration
« Reply #7 on: December 29, 2005, 02:36:50 PM »
The cables were probably on the unit but just didn't get sprayed. Someone might want to check if the mounted end of the cable had paint on it.

2-cents
Buddy

william

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Re: 12 bolt restoration
« Reply #8 on: December 29, 2005, 03:50:48 PM »
I have dismantled many 12 bolt axles over the 15 years we had the business. I never saw paint on any part of a pb cable.

JohnZ

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Re: 12 bolt restoration
« Reply #9 on: December 29, 2005, 03:51:22 PM »
When we hoisted the axle out of the shipping rack, the cables were crosswise horizontally across the axle, above the diff nose, and held together with a wire tie so they didn't dangle and get hung up in the rack locators; after setting the axle on the chassis carrier and installing the springs and cable guides, we cut the wire tie, routed the cables, and clipped them into the guides. The cables may have been hanging free when the assembly was painted while on the conveyor at the axle plant, then routed and wire-tied before the axle was transferred into the shipping rack.  :)

nuch_ss396

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Re: 12 bolt restoration
« Reply #10 on: December 30, 2005, 01:14:35 AM »
The rear axle assembly (housing, tubes, diff, rear cover, backing plates and drums and parking brake cables) was painted at the axle plant as a completed assembly just before it was placed in the shpping rack; the brake pipes and center block were installed later at the car assembly plants.

John,

Is it your considered opinion then that the entire rear should be painted the same percentage of gloss black?  While we are on this subject, what
do you consiider the closest paint ( gloss content ) for the rear axle assembly? 

Steve
69 SS 396, Hugger Orange, D/80, D/90
Chambered Exhaust, N/66, THM400, 3:73 posi

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dews 67

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Re: 12 bolt restoration
« Reply #11 on: December 30, 2005, 02:10:29 AM »
So is the driveshaft flange assembly natural in color? The part that is attached to the pinion gear.

william

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Re: 12 bolt restoration
« Reply #12 on: December 30, 2005, 02:17:14 PM »
As I stated previously the driveshaft flange was not painted. It must have been masked.

dews 67

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Re: 12 bolt restoration
« Reply #13 on: December 30, 2005, 02:55:48 PM »
Thanks. Just making sure.

JohnZ

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Re: 12 bolt restoration
« Reply #14 on: December 30, 2005, 04:17:07 PM »
I'd call the axle paint semi-gloss; the pinion flange was masked with a thin cardboard tube to keep paint off the U-joint cap seating surfaces - every now and then we'd get an axle that still had the tube in place.  :)