Firebird and the Trans-Am series

[Swede70]

Hello,

Outside of what we've seen, do any other images exist that might capture the appearance of the Watts link center pivot structure built and situated between the rear subframe rails aft of the axle assembly?  It seems vaguely Kar Kraft inspired for having a discernable sheet metal structure versus welded tubes ala the RKE JRT Javelins, although I don't know if what I'm viewing bears structural members within.  A visit to the German Boss 302 Trans Am website allows one to view a photograph of an unrestored '68 KK constructed Mustang, so at the least it seems that they employed a stable design across '68-'70.  Sorry to be cheeky - just a model car enthusiast pondering how and what to fabricate.  Kind regards and thanks everyone for sharing their knowledge and insight.  

Mike K.

[Bruce302]

Mike,  The centre pivot mount is made from square tube that runs between the rear frame rails, and it is covered with aluminum sheet.
I may have a photo somewhere of the frame work without the covers on.

One of the key fabricators of the T/G Firebirds was Jerry Schwartz, he was with Shelby prior to that so it is very possible that shared Mustang build features could cross over from KK and be used later and be very similar.

Bruce.

[mark x22]

Do you have a picture looking at the end of the axle tube ?

[Jon Mello]

Are you asking about whether or not the axle tube tapers down where it meets the 4-bolt flange at the outer end?

[mark x22]

In post 43Bruce said they used F body tubes . Are they drum brake or Jl8 tubes ?

[Bruce302]

Best way to answer that is show you the pic, looking down on the right hand axle tube and flange.



Bruce.

[Bruce302]

Outside of what we've seen, do any other images exist that might capture the appearance of the Watts link center pivot structure built and situated between the rear subframe rails aft of the axle assembly?

Mike ,  Here is a shot of the underside. It shows the frame work for the Watts centre pivot. The fuel cell is right up against the rearmost part of the frame (closest to the camera) The front (away from camera) and underside are panelled with aluminum.



Bruce.

[Swede70]

Thank you very much Bruce - this is perfect,

Much better then I hoped, I really appreciate the images and explanations.  Surely I can proceed with fabricating the structure of the same.  It seems when Titus defected from Ford he took some other disaffected personnel away with him, and given the debacle of the '68 Shelby Racing Co. season, little wonder.  Kind regards...

Mike K.

[Jon Mello]

Bruce's rear axle tube is not a Camaro piece. Looks to be Pontiac but I'm not sure if it's Firebird or borrowed from something else.

Below are the JL8 bracket and drum brake backing shield. On the JL8 bracket, the distance between the upper pair of holes is 3-3/8" or approximately 86mm.
The bottom pair of holes on the JL8 bracket is the same distance across (3 3/8").
On the Camaro drum brake backing plate, the distance between the upper pair of holes is 3-3/32" or approximately 78.5mm. The lower pair of holes are
closer together and measure 2-21/32" or approximately 67.5mm.



I'm going to take a guess and say Bruce's flange hole pattern is neither one of those and that might be why they had to fabricate their own caliper bracket.
Bruce, if you ever get a chance to measure that bolt pattern, let us know what you find out.

[Sixteen Grand Sedan #56]

All 68-9 Firebird rear axles I have seen have the same large impression in the top of the axle tube just above the spring perch area as shown in the picture above. This appears to be to give the rear end more movement before it hit the rubber stops mounted on the frame rail. The 67 Firebird rears do not have this impression. The center section also has the round mounts for the bushings to mount the upper control arms used with a coil spring application. These are left empty on the Firebird applications. I do not see these in the pictures so either they were cut off or the center cast section is from another application. If the carrier has a 12 bolt ring gear then that is what I would suspect.

The standard Firebird used the smaller 4 bolt pattern to mount the backing plate, same as the Camaro. My guess is that is why they fabricated their own mounts. Since the standard Firebird used the retainer style axle bearings the axle tube does not have the same "dip" as seen in the standard Camaro rear ends. The "service package" JL-8 rear had the larger diameter axle bearings and thus did not have the "dip" near the end of the tube . Both production and service package Camaro JL-8 rears utilized the larger bolt patten because they were adapting the Corvette brakes. Measurements from Bruce will tell us more.

The

[Bruce302]

OK, I had a quick measure, The distance between the upper and lower bolts of the caliper mount, bearing retainer is 2.5" and without checking i assume they are the same all around.

The 'ears' on the upper side of the centre section where the bushes for the 4 link mount, have been milled off. I hav a pic of that some where.
There was zero co-operation between Chevrolet and Pontiac during the time these cars were built. Being part of GM meant absolutely nothing when it came to market share and sales. My good friend Rob Irvine was in Chevrolet parts (dealership) and did get some good pieces for the Pontiac racers (T/G) but when asked who was ordering he named a local Camaro racer so he wouldn't be considered a traitor.

The axles would have used only Pontiac parts, or parts made specifically for the T/G team.
Bruce.

[Jon Mello]

Thanks, Bruce. I measured the distance between the upper set of holes and the lower set of holes and for the JL8 bracket the distance was 2-5/8" or approximately 66.5mm. For the drum brake backing plate, the distance was 2-13/32" or approximately 61.5mm. Looks like yours is unique.

[Bruce302]

The best part for me Jon is that this unique rear axle was separated from the car for 25 years. It was found and re united with the car.

Bruce.

[Jon Mello]

A nice stroke of luck, Bruce! Not only fortunate for you, but for us Trans-Am enthusiasts as well. We get to learn more about the T/G cars than we otherwise might have been able to do.

[Bruce302]

It certainly was a crazy set of circumstances that saw me re unite the car and axle. the guys that had it only knew it was a Pontiac, and it looked like a 10 bolt. No body wants them, ever.

As soon as I saw that rear cover I knew it was THE piece I had to have.   

Bruce.