1955 back end is loose when hitting bumps

[JOHNGRISWOLD]

I have a 1955 Tbird that has had a lot of work done to it. If it drove as good as it looks, I would be done now. I have all new front end parts, heavy duty sway bars front and rear. New springs front and back, and a Unisteer power rack and pinion steering system in it. problem is the car feels like the rear end wants to come around on me when hitting bumps? I put more positive caster vin the alignment, played with tire pressure, but nothing seams to help! I am wondering if any body has an idea of what I am fighting? or any suggestions?
I am thinking I may need an old school 4 wheel alignment center to rack and align it!

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[55birdman]

I’ve done nearly the same modifications along with some stouter shocks and 16” wheels (to clear disc brakes) & tires.
I’m wondering is the rear suspension is too stiff as I get a similar reaction going over bumps, etc.
Maybe we should try putting a few sandbags in the trunk to see if that changes things??

 

[biddle]

@JOHNGRISWOLD "1955" is not a summary of your post. When you post to the forums, your subject should be a short summary of what your post is about along with the four-digit model year. If nobody knows what the post is about you won't get many replies.

I will update it.

 

[74 Harley]

What type of shocks are you running?
If you have modern gas charged shocks pull them off and get a old school shocks.

 

[55blacktie]

Johngriswold, considering all you have done to your car, putting "old school" shocks on it would be counterproductive. I'm assuming that your parts were designed to work together. Before swapping parts, find that "old school" alignment shop or a shop that routinely deals with custom, classic, or performance cars. If alignment won't take care of your problem, maybe they will be able to recommend what needs to be done.

I have similar parts on my 55-Hotchkis front/rear sway bars, Bilstein shocks, Aerostar springs, Granada 1 1/2" drop spindles, Traction Master under-ride traction bars, new leaf springs, 215/70r 15 tires on 15 x 7 wheels, and all new/rebuilt steering components and bushings, but my car is not yet back on the road. I intend to trailer it to an "old school" alignment shop before taking it on the road.

Let us know what it takes to get it dialed in.

 

[Ward 57]

Even with my '57 with more weight over the rear than the '55 mine wants to act the same way even though it is stock. These cars are front heavy and the rear wants to wiggle. The '56s with all that weight out back made the handling worse. That's why the Continental kit was a one year feature.
You may just be dealing with 'That's the nature of the beast'. They were designed as boulevard cruisers and not true sports cars. You may have to learn how to drive it as it is and understand it will never handle like a newer car.

 

[55blacktie]

John, by any chance did you invert the leaf spring shackles? I've seen it done on a few Tbirds to increase the rear ride height. If so, that could, at least, be contributing to your problem. Also, if the shackles are inverted, hitting a big enough bump/pot hole could cause the shackle to revert to its proper position. If that happens, that side will then be lower than the other side, which could upset balance and handling. I don't like the look of the springs and shackles hanging down where they shouldn't be; they could also drag/bottom out.

 

[paul5456]

Check the nuts on the U bolts holding the springs to the axle

 

[JOHNGRISWOLD]

@JOHNGRISWOLD "1955" is not a summary of your post. When you post to the forums, your subject should be a short summary of what your post is about along with the four-digit model year. If nobody knows what the post is about you won't get many replies.

I will update it.

View attachment 23685

I appreciate the info. This was my first attempt at posting ever! lucky someone saw it.

 

[CSPIDY]

Check the nuts on the U bolts holding the springs to the axle

This is good advice,
if the rear springs were removed or replaced
it may take several retorques to keep them tight
if loose the rear end can slide on the spring

 

[JOHNGRISWOLD]

I did recheck all the U-bolts and attachment hardware, found some needed to be retorqued. Car still has same issues.
Thanks for the response

 

[55blacktie]

Broken/defective shock?

If your rear sway bar is too big/not matched to the front sway bar, it could be causing oversteer. You might consider test-driving your car without the rear bar to see if that makes a difference. The larger front sway bar/w no rear sway bar will induce understeer.

 

[JOHNGRISWOLD]

I want to thank all of you that have responded to my posts. I will double check all the nuts, bolts in the front end and the rear end. I had the same steering issues with the stock front end parts, however now with the power rack and pinion this problem is more profound. I n\know the springs I installed were heavy duty, and that in itself may be a problem!
I ordered some medium duty springs from Eaton, I may or may not have to adjust the ridding height in the front? I would like to get the cars c/g back to where it should be! wright now the front end is to high. I will continue to posts up-date on the progress of trying to get this Bird to handle better!
thanks