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View Full Version : 1st Gen F-body: Prepping a 12-bolt Suggestions for a swap



MyFriendScott
07-03-2011, 06:36 AM
One of the goodies that came with the purchase of my friend Scott's '67 Camaro was a spare 12-bolt with original Eaton posi, and 3:73's (Richmond gears, not factory). The axle flange to axle flange measures 60" and I believe this should be the same distance as the 10-bolt in the car now. I used this link as a reference:
http://www.quickperformance.com/Technical%20Info/sus_measure.htm

The leaf spring perches have a centering pin hole in them so I'm guessing based on the info and decoding the numbers, this 12-bolt came from another Camaro or Nova. Since Scott also had a highly modified '69 RS, it might have been the original 12-bolt that came in that car before he stepped up to a new unit. Of course, I can't ask him now so it's all been decoding numbers on the axle housing, removing the diff cover, and also spinning the yoke and counting the axle revolutions to determine what I have.

So...Since I'm stepping up to a new tire/rim combo that's 1" taller than what's in the car now, I decided now would be as good a time as any to get the 12-bolt ready to gain back the gearing and the obvious other advantages of using the 12-bolt. One thing I haven't measured yet are the spring perch distances to make sure there are no surprises.

Are there any other areas I need to consider as I prep the 12-bolt for the swap? Can I still use a mono-leaf made for a '67 in this axle if it is in fact from a '69 Camaro? Are the leaf widths different? I'm pretty sure the '67 monoleaf that's in there now doesn't use a centering pin either. Thanks in advance for all/any advice.

MrQuick
07-03-2011, 11:17 AM
You can still use the perches...a set up like this will keep everything in line. http://www.detroitspeed.com/1967-1969%20Camaro-Firebird-Products/041101-mono-cnvrsn-kit.html

On my 67 I cut the mono perch off and replaced it with a bolt on unit from Speedway since I was going with a mini tub and moved the rear shackle mounts in.
http://www.speedwaymotors.com/Clamp-On-Spring-Pad-For-3-Axle-Tubes,35921.html?parentDisplayId=632

MyFriendScott
07-03-2011, 12:03 PM
Cool, thanks for the reply. About the Detroit Speed kit, is that for going below the leaf pack? It looks like the locating pad with the hole gets sandwiched between the bottom of the leaf's mounting pad and the lower shock plate. If that's the case, couldn't I just get new lower shock plates with a hole in them like these:
http://www.speedwaymotors.com/Speedway-Lower-Shock-Mounting-Plate,3528.html

MrQuick
07-03-2011, 12:17 PM
yep, but you will have to make something to fill the gap and keep your plates from taco'ing when you tighten the bolts.

MyFriendScott
07-04-2011, 12:59 PM
I ended up buying a set of Detroit Speed lower shock plates for a stock 67-69 non-staggered shock configuration. These are the plates:
https://static1.pt-content.com/images/noimg.gif
I also picked up a set of polyurethane multi-leaf pads from Rick's
https://static1.pt-content.com/images/pt/2011/07/UR6-1.jpg
And the multi-leafs I choose are the Hotchkis 1.5" drop multi-leafs spring kit. I think I got everything accounted for at this point. I'm going to reuse the brakes and brake lines on the 10-bolt. I think the only thing that could trip me up now is if the pinion yoke is closer to the tranny than the 10-bolt. I haven't found those reference measurements yet.