1st or 2nd Generation Firebird rear suspension modification?

I have a 2nd gen posi disc rear I will be looking to outfit for my 1st gen with total hotchkis springs on all 4 corners.
What are some of your experiences with cal tracs, lift bars, slide a leaf?
.
I wanna know some of what you all have done to help plan for this swap and upgrade.
What have you found works not work etc...?  
Viagra and Torque are one in the same they both get you up!

rear end widths.  is the newer rear end going to be too wide?? or have you contemplated that..

60.00 1967-1969 Camaro
60.25 1968-1979 Chevy II/Nova
60.50 1984-1995 Corvette
60.50 1964-1967 Chevelle
62.00 1955-1959 Chevy Pickup
62.50 1968-1972 Chevelle
62.50 1970-1981 Camaro/Firebird


i recall an article.. probably 15 or 20 years ago... on the changes made for the 3rd generation 7 1/2" australian build trans am disc brake rear end...  as they needed to limit end play to keep the calipers from needing to slide constantly as the car corners...  went to a bearing retained on the axle like the 67 to 69 firebirds have..  the chevy camaros came with a C clip rear end..

its been too many years since i worked on the rear disc brakes of a second gen firebird... to recall how they limited end play to keep the pads from rubbing..

i know that the sevilles and eldorados with similar rear calipers had terrible issues with the rears calipers not adjusting..  i just don't recall that happening with disc brake trans ams.. but i only worked on a few.. i did a LOT more caddy service ..   i figured a way to adjust them without removing more than the rear wheels...  even did some special mods to tools..

others will know how strong the BOP rear end is... thats probably in your car now..   this is just a warm up answer... expect a lot more..  

Point taken. Didn't consider the axle was wider.
I took measurement from center leaf bracket to bracket and it matches other than width of my leafs are wider.
I will have to check that measurement.
Thanks.
Anything else on the traction devices and experiences with them?
I have south side machine lift bars and they are stiff but I spin the rubber like I have john forces backing. Which I'm just as poor as the next guy doin budget building.
But I couldn't pull better than a 2.1 60' time... Make up for it after the 1/8... But kinda wanna hook.
Not sure what hotchkis leafs have done for that.. haven't been on the track since changing the old re arched ones out.  
Viagra and Torque are one in the same they both get you up!

rectangular slapper bars do work if the snubber is up under the forward spring eye...  so its lifting on the body instead of trying to bend the spring backwards..

they usually need to be extended..

does your firebird already have multi leaf springs???


please keep an eye on the mounting locations in the body above the spring perch bracket..

i have seen several cars rip them loose..

there is a neat subframe extension that has bracket ends that mount above the spring perch  and gives you a place for rear suspension mounting..   a drive shaft loop..  along with the subframe connectors...   it normally plugs in the end of aftermarket brand subframes..

creative builders could make their own... that works with a factory subframe..  with 4 tabs up front a section that slips into the end of the subframe tails... and mounts to the pockets for the forward spring perch..  that would not even be that hard to build...   could even have the brackets over the top of the subframe that hang down slightly to allow a easy drop crossmember for the transmission..

or sandwich it within the rubber body mounts..


when you mention the lack of traction...

there are a LOT of factors to consider...

are both wheels locking with some kind of locking diff.. or is it one legged..

if you only run the car on the track...  and you have a big pile of side shims for the side and spider gears.. you can assemble the differential gears too tight clearances because of too thick shim selection .. with a brass or plastic hammer to drive the spiders around inside the case to snug up everything.. this expands the case and tightens the side clearance on the carrier bearings... can also change your gear lash. as the long side of the case spreads and pushes the ring gear away from the pinion slightly..  if i recall..  poor mans posi..

do you have enough rubber where it meets the road...

does the back end of the car lift or drop when you drop the loud pedal????

does the front end of the car lift or drop when you drop the loud pedal..

there is a really good book on drag race suspension..  probably from chassisworks.. i have not seen a copy in a long time..  it described the instant center of where the rear axle pushes the car..

i think they used a fridge as a subject...   if you push at the top... you knock it over away from you..

if you push at the bottom.. you knock it over on you...

if you push at just the right height...   its easy to push across the room without it tipping either way...

just slightly below center of gravity is where you want to have the instant center at ..

its been too many years for me to go deeper into it ... but you just barely want to the front end to lift. . if the front end lifts to much.. you are wasting motion going up with the front end instead of moving forward..  but again.. i could be totally wrong..  

Thanks...
More background on what's in place.
3.23 posi.. its in or was before being garaged for 12 years...
If memory serves when I last did the diff drain and fill it was in good shape.. no major play.. metal in the old etc..
Again last service, tune up, timing adjustment was over a decade... Oil as well! Garaged ... Started a few times a year to idle.. some questionable back street cruises at varying rpms to make sure nothing was leaking or dry rotting.

Leafs were installed during garaged days... Had the front & rear hotchkis springs finally got time about 7years ago to install them.. car sits and rides completely different..
Multi leaf btw.
South side machine lift bars go to the Base of the diff u bolt over axle tubes and has a box clamp to the front of the spring with shim.
It's not right on top of the front mounting point but close. Have subframe connectors bolt in style but welded as well.. buddy did that during resto on it back in 96.
Car lifts up front not wheels off ground unless I loosen the end links like track days.. I would give about
1/4 to under half inch of play on them at the track and snug back up once loaded onto the trailer before heading home... Last thing I made a habit of. Don't need loose front end on street like that.
Hard to guage where the bird is at lately.. rear end around corners gets squirrelly. Car has so much power it car break the tires loose easily.
Slicks... Mickey Thompsons ... I would roast just trying to heat them up to try and get them sticky.. even went down to 8psi in them.. which wasn't an improvement and I found a lot of wobble at the end of the 1/4 I didn't like at those speeds.

I did a lot of test and tune and had a good feel for the car. . life just led me a different way and I never solved the whole problem with hooking up.. I left it in a garage for an older me to fix I suppose.
I wish I had my notes I kept...  I went as far as different heat range plugs in certain cylinders for optimal performance.. I tried a lot of old school tricks from the F.O.G's... (Fat Old Guys) that used to race these back when and owned racecars that sat at dunkin donuts on a cruise night drinking coffee and BS-ing about everything they owned and built..
Wealth of knowledge on DO's and Don't.
Now I'm in the H.O.G. stage (heavier older guy).. but missing key links as to what I did because wife or mother in law threw out or mispacked a notebook I kept what I did and didn't want to do again.
So.. I'm starting over... But way ahead because Engine and Transmission are in top shape.
Again... It's a nasty launch... I just never saw 2.1 60 foot as a good one... and with 3.23's leaves me wondering had I gone to 3.73 back then how would I have kept it out of the wall!
Still a concern looking to go to the 3.55 now. Not so much wall... But ditches, curbs, trees.. you get my drift.

Starting back at the foundation and will work my way back up.  
Viagra and Torque are one in the same they both get you up!

it still goes back to does the front end lift and the rear suspension digs in...  or does the rear suspension lift the back of the car so quick that the upward movement pulls the tires up and allows them to break loose..

want to see something that looks totally wrong and painful  

look at some footage of the transam corvettes that are kicking the others out of the way right now..

look at how loose the damping is on the rear...   this allows the back of the car to up and down massive amounts while the wheels are still biting the track....   it looks ugly and painful for the driver as he is subjected to massive amounts of ....... sort of a reverse motor boating effect as the back of the car looks like they left the shocks off.....

push down on the rear fender.. does the rear suspension move ... give...

i saw a friend do some back alley testing for launch...   they not only painted stripes on the sidewall..  they had the tires on a wheel balancer.. hand spun it up and painted stripes on the side wall..  matching lines were masking taped to the outside of the fenders... set up with a level...   they were all 1 inch wide stripes...  they could see the deflection of the slick sidewalls and if the suspension went up or down when the launch happened... they could also see the relation ship of the body over the suspension.. as they used their VHS cam corder on 1000 Frames per second and a view of the side of the car ...  most HD CAM CORDERS have that or even a faster setting...

decades ago.. i was with a funny car team... the guy with the superstock dodge dart in the next pit.. looked to have a lot of air in his slicks...  i ask him when we had a few seconds... he said he runs 32 PSI in his slicks...  does not like the way the back of the car wobbles at the top end..  

I can relate to the Dart Guy! I didnt like 8PSI at the end of a 1/4 and that was probably higher after burnout, launch, and run!....
But the back end is still stiff.. Its been ages to tell you whether or not its buckling and giving way under launch.
I have no way to give that reference.. its been 12 years and blowing sunshine your way to truly give an honest opinion or for advice is just not right.

I will have to strap a milk crate to the floor board and pull a burnout on the street.
j/k
But when I get the floor boards finished hopefully withing 2/3 weeks.. I will revisit this thread with more than speculation.
I have no "intention" if doing a 1/4 mile but that bug-bite has been itching me for the better part of 12 yrs too.  
Viagra and Torque are one in the same they both get you up!

it is all about pinion angle. 5 to 8 degrees down at rest, 2 deg down at launch in relationship to the drive shaft. too far up or down and you are a john force look a like! and if your rear springs are too soft,(mono leafs) the tires lift in to the wheel well. no down force on the tire.
i had the same problem with a 67 fb and a torq monster 462 when i was young and ignorant. later in life with a 74 firebird 468 /th350 ,3.50 gears 1.7s in the 60'(slide a link) consistant 11.50s at 118. about 3" of air under the front runners at the track only.  on the street i would roll on the gas short shift to 2nd, always had to run them down.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD