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Discussion Starter · #1 ·
Gonna try to document as I go

I have a 1967 fire bird converted to 4 speed with open end 2:56 rear

I already changed to the 1979 multi leaf springs

I now obtained a 1979 3:23 posi track I want to use

First thing I did was remove the factory track bar and set it aside

Next I undid everything and removed the rear

Here is a pic of the rears

Bottom is 8.2 top is 8.5

The rears look same length, and it appears the second Gen perches only need to move an inch or so

I will post more as I go
 

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There was 1" of slip in the drive shaft at the trans, was gonna post that when I got to the drive shaft

Also the 67 rear uses u bolts to hold drive shaft to yoke, 79 uses bolts and straps
 

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']['exXxas']['itan
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Will a 2nd gen camaro rearend be the same as the firebird?
 

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Tom in the process also. Disc brake rear 3.73 gear. You said the emergency brakes sucked on the 2nd gen so I am going forward without them. Not ideal on a 4 speed car but not bad in Florida where it is flat. Ordered new perches for it. I got the 2nd generation shaft for it. It is supposed to be the right length. I don't know about the 2nd generation yoke size. I will have to check to see if that will work or if I need a spicer u joint.
 

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Discussion Starter · #6 ·
The second Gen disc rear calipers are very prone to leaks in my experience and they use a ratchet type park brake where you need to push and twist the piston iirc , been a while
Here is the 67 rear set up on stands and level at the spring perch, there is 7* pinion angle, I checked in several spots and came up same 7*

Be sure everything is scraped off and clean when doing measurements like this
 

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Discussion Starter · #7 ·
Just setup the second Gen rear (1979) pinion angle is 6*

When I mock up the rear for welding I will shoot for the 7* of the first Gen rear but I am sure its fine as long as u are in that 6-7* range I do not see there being a bind issue there and its not like you have steering angles to contend with

I also had this way jacked before with lift shackles which seriously changed the pinion angle with no ill effects
 

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']['exXxas']['itan
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Don,

On your 12 bolt, was it narrowed at all? Im not sure of the axle flange to flange length on them. Ive been looking all over for a used 10 bolt that I could build up, but all I keep finding are 12 bolts out of A bodies Grrrr! Found 1 68 camaro 12 bolt but it has damaged tubes on it (crimped).
 

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Discussion Starter · #10 ·
Some progress today

Removed the perches from the second Gen, they were mounted approx 11" from carrier section see pic

I ended up cutting the perch welds with a 4" grinder no guard and a 6" cutoff wheel ( be very careful wear glasses and heavy gloves)

The center of each perch is tacked on the tube but also plug welded in the center,cut the tack on the tube then use a metal chisel and heavy hammer to break that center weld

Next I ground down remaining welds on the tube then went back and filled any imperfections left in the tube from the removal of the perches, then ground those welds and followed with a flap disc and primer

Cleanup of the perches was done best I could with a wire wheel (blast cabinets down) and drill press to drill out the center plug weld
 

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Discussion Starter · #11 ·
Rear is in and perches are tacked, carrier measures same width both rears so I tacked the perches 10" from the carrier same as 67 rear and set pinion angle 7* same as 67 rear

Also great news I picked up a drive shaft from a 79-81 z28 with auto trans (350 turbo I guess)
Perfect fit !! There is 1 1/4" of slip in the yoke , the old setup had 1" slip I find this acceptable
 

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So other than pull the rear and recheck pinion angle/ weld perches and reinstal that's all there is to swapping the rear

I am waiting on new urethane perch pads before I final weld to be sure everything is just right since I basicly looked through the weld hole in the perch and centered that over the pin in the spring then clamped the perch to the spring ( wire wheel on grinder clean all crap off that area of the spring)I do expect the perches to move a little from where I have them with the perch pads in place but not enough to make a difference
 

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Weathers been kicking my butt and times been limited, I ordered a prothane kit with shackles for the rear springs, kits for second Gen multi leaf, we removed springs cleaned painted and new bushings,remounted springs

It looks like we used the first Gen front spring mounts on the second Gen springs

Now I also bought the prothane spring perch pads to fit second Gen, only issue there is if you are reusing the first Gen lower mount plate the hole in the middle will need to be enlarged, a big uni bit worked well here

***** if while trying to remove the front spring perch from the body the bolts spin you will need to remove the rear seat and measure where the bolts are and cut holes in the floor, these
Bolts are held with a u clip with a nut welded to it, u clip breaks and nut spins

Stock u clip has a nut that takes a 9/16 socket ****** bolt is 3/8-16 thread
 

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Discussion Starter · #17 ·
As for the rear brakes, if you retain the drum setup, the drums, shoes and hardware swap over
The 67 wheel cylinders don't fit the 79 backing plate, the arbor pin mount is different, I could probly make the cylinder fit but they are cheap

I bought AC delco and of course got a defective one

In the pics new/painted is the second Gen, rusty is first gen
 

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Discussion Starter · #18 ·
Update here, test drove the other day and everything seems gtg on the rear swap, the change in gearing is also a huge improvement, cars finally slowly getting where I always wanted her to be :)
 
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