Packard Forum Index » Modification Discussion

This thread documents the adaption of more modern front and rear anti-sway bars to the Torsion-Level chassis of my Panther (nee 1956 Clipper).

The first question would be "Why?" I will grant that a T-L Packard probably handled better than any other mid-1950s big car just based on the T-L suspension alone and that's one of the reasons I and many others like them. However, there's always room for improvement. Given that, the question becomes: "how to improve it."

Mid-1970s Firebirds, particularly Trans Ams, were outstanding handling cars. A stock Gen-2 Trans Am was capable of negotiating a skid pad test at around 1.0G, which is beyond what most drivers are capable of utilizing. Since I used to have some of these Firebirds as parts cars, I figured I would start there. Below is a picture of the front subframe of a 1981 Firebird inverted right before it got sent to the metal scrapper. This shows what the front sway bar looks like and how it is attached.



The next question is "how do you adapt it?" The frame rail connections are about the same comparing the T-L Packard to the Firebird, although the distance between mounting points is somewhat different. However, the sway bar end connections are quite different. Of course, I mocked up how the mounting might align just by hanging the Firebird front sway bar onto the Panther chassis with coat hanger wire:





This mockup indicates a "GO!".

The most difficult part of the adaption will be how to mount the ends to the Panther front lower control arms. This is what I did.

I cut and modified a length of steel "U-channel" from the local Home Depot into a couple of "outriggers" to connect the lower strut from the Firebird sway bar to the Packard lower control arm.





Here's the finished outrigger bolted to the lower control arm with the Firebird end link attached.



One also has to mount the attachment of the sway bar to the front frame rails. I used a pair of 3FT steel "L-channel" from Home Depot as the crossmember. The mounting locations is somewhat different than Packard's T-L front sway bar, but the idea is essentially the same.



Here's a "down close and personal" view of the result:

Are the Pontiac bars larger in diameter than the Packard bars?

Will you be able to turn your wheels with the tires on the rims? It looks tight in the pictures.

Does having the mounting points of the Pontiac bars out further on the frame than the stock Packard bars create any issues?

Well, the adaption of the Gen-2 Firebird front anti-sway bar to the Panther went pretty well. Now on to adapting the Firebird rear anti-sway bar.

One might ask: "Why a rear anti-sway bar also, especially since Packard did not use one?" Or one might think that the "S-bar" linkage in the rear of a T-L car is some sort of anti-sway bar too. It is not. It is technically an "inverted Watts linkage" whose sole purpose is to assure the central location of the rear axle under any up/down movement. It has no anti-sway purpose whatsoever.

As to why a rear anti-sway bar also: This is for handling balance. The stock Packard front anti-sway bar is 7/8IN in diameter. The stock Gen-2 Firebird front anti-sway bar is 1.00IN in diameter (the smallest available). This doesn't sound like much difference (1/8IN), but because torsional rigidity increases as the FOURTH POWER of the diameter, a 1IN torsion bar (anti-sway bar) is 70PCT more rigid than a 7/8IN bar! If I don't install a rear anti-sway bar, Panther will "push" badly in turns because of too stiff anti-sway in the front.

As with the front Gen-2 Firebird anti-sway bar, I mocked it up by hanging with coat hanger wire. I won't show any pictures of that because it's pretty self evident except to say it looked like it would work except that the Firebird strut-to-frame length was 4IN too long compared to what I needed for the Panther. So, I had the machine shop shorten (cut and reweld) the struts. Here's a picture of the stock (front) and shorter struts:

Mounting the upper end of the Gen-2 Firebird strut to the existing crossmember was "cake". All I had to do was cut off a little of one end of the bracket, drill corresponding holes in the crossmember and bolt it together.

Mounting the bottom of the Gen-2 Firebird anti-sway bar was more work, but came out very well.

I used the existing hole in the rear axle tube mount-to-trailing arm as one point. I had to temporarily separate the mount from the trailing arm in order to remove the rubber biscuit and washer and trim same a little bit to make room for the head of the outrigger mounting bolt, as shown:



The outrigger was pretty simple, but it had to be robust. Here's a few pictures showing the sequence of parts and their install:

Here's the entire Gen-2 Firebird rear anti-sway bar mounted with the Packard S-bar and shocks:





Any questions or comments welcome.

Craig

Let the ride decide Quote:

Good Qs all!

Yes, the Firebird bars are 1IN & 3/4In front/rear. The Packard bar is 7/8IN front, no rear bar. One can get larger Firebird bars if that is what road testing indicates and swapping them will be no problemo.

Quote:

Yes, it looks tight in the pics, but that was one of my major criteria. No problem left-right lock-to-lock, even with the disc brake calipers mounted on the front and the fact that I will be using wider wheels and tires than my mockup/roll around. Check the mockup picture top view:


Quote:

Yes, the mounting points of the 'Bird bar is slightly different than the Packard, but it's pretty minor. Look at your car and you'll see. The main factor for anti-sway bars is bar diameter and the distance between the mount points on the frame (the "twist distance", if you will). I expect that I may have to do some fine tuning later vis-a-vis bar diameter.

Craig

I'm wondering if anyone has ever installed the rear bar before and curious how the bar will affect the ride and TL.

I could see where the bar might improve or reduce the body lean on curves but wonder if the overall ride will change much. Don't pretend to know much about suspension and interactions and will take your word it is needed to work with the heavier front bar. Packard literature mentions the reason they chose the Watts linkage was it allowed true vertical movement of the axle but would not transmit any lateral forces or "harshness" to the frame. Seems like the added bar would counter that aspect and stiffen the ride considerably.

Howard Quote:

Anti-sway bars do not affect the ride at all unless the body is trying to sway. They are just "along for the ride". As the chassis/body is moving up/down without sway, the bar is just pivoting in its brackets and introduces no force anywhere. Only if there is sway does the bar twist to try and counteract that sway.

Quote:

Nope. See above explanation.

Craig