Car sways under hard acceleration

[Curiousyellow71]

My Charger when I run slicks the back is shifting back and forth. You can also feel it with street tires..just not as bad. It has air shocks yet which could cause it..? I had u bolt slapper style tractionbars at one point with a 4.88s and a 5000 stall and it broke the u bolts on the traction bars. Car starved for fuel...died and coasted through the traps (stock fuel tank) but still ran a 12.3 at 99 it was on a 11 sec pass. But the car has swayed ever since. We may have broken a spring at that point....but nothing is obvious...its terrifying w slicks. Front suspension is really high under acceleration...maybe the ride height is effecting the alignment?
Any ideas before I start swapping parts?
Thanks,
Ty

 

[69roadr]

My Charger when I run slicks the back is shifting back and forth. You can also feel it with street tires..just not as bad. It has air shocks yet which could cause it..? I had u bolt slapper style tractionbars at one point with a 4.88s and a 5000 stall and it broke the u bolts on the traction bars. Car starved for fuel...died and coasted through the traps (stock fuel tank) but still ran a 12.3 at 99 it was on a 11 sec pass. But the car has swayed ever since. We may have broken a spring at that point....but nothing is obvious...its terrifying w slicks. Front suspension is really high under acceleration...maybe the ride height is effecting the alignment?
Any ideas before I start swapping parts?
Thanks,
Ty

Need to drop more coin in the car

 

[MoparLeo]

Throw the airshocks away. Put new springs on that are the proper rate. Fix the front end and after the car is in good mechanical condition, start to work on making the suspension work for you.

 

[Curiousyellow71]

Thanks for the replies!
Everything in the front is new other than the steering box. I have seen fast passes on stock springs. The ride height I would like to keep level front to back. Anyone have a spring recommendation for that? I figured someone has had this same problem. Have a fuel cell and bigger line now probably a mid 11 street car if I can get back to a sticky tire.

 

[Kern Dog]

Front suspension is really high under acceleration...maybe the ride height is effecting the alignment?

The alignment does move around a bit with suspension travel. At full extension, the caster goes negative even if you had 2 degrees at static ride height. Negative caster will give a real spooky handling feel.
The "anti dive" built into our cars upper control arm mounts is such that as the suspension extends, the upper ball joint travels down and forward. This is yet another reason why it is important to adjust in as MUCH positive caster as you can.

 

[droptop]

Check the upper rear shock mounting bracket. That is light weight sheet metal and not made to handle air shocks. If that is ok, put a pinion snubber on it.

 

[vance.dykes]

if you are going to drag a mopar do your self a big favor get the mopar chassis book it will give you your alignment and what to do with the rear. i ran a stock fuel tank in to 11:90's remove the sock on the pick up and keep the tank full and you wont run out of fuel more weight on the rear gives more hook.

 

[66Satellite47]

Air shocks & slapper bars are not for Mopars. Scrap that stuff. The leaf spring design of Mopar is far superior to GM & Ford for acceleration. IMHO get some new ESPO springs & good adjustable rear shocks. Have the alignment shop check the toe change as they jack up the K member. Max out the positive camber.

 

[Curiousyellow71]

The camber is probably the problem. Jacking it up while they align it is a excellent idea. The slapper bars were a bad experience years ago and I maybe tried them 3 time before the car freed itself of them. It literally broke them off. Upper shock mount good yet. The car squats so much I think the stock pinion snubber hits.

 

[Curiousyellow71]

I do have experience drag racing a mopar. Use to race a 10 sec 70 cuda. But it had ladder bars and the skinny front tires made it drive great. When I first tried traction bars with slicks on the charger we were running a roller cammed 440 with a trans brake. After that race the drivetrain came out and was put in the Cuda. Charger been a street car ever since.

"Spooky feel" from the camber changing is a excellent description of how the car drives. I am sure I have a mopar performance book somewhere.

 

[Kern Dog]

It isn't just the camber that makes it wander, it is the caster.

 

[miller]

Add toe to the list.

 

[66Satellite47]

The car squats so much I think the stock pinion snubber hits.[/QUOTE]

Mopars normally don't "squat", the rear of the car lifts. If the snubber is hitting the floor pan you may need a different pair of leaf springs, too much axle wrap up. IMHO

 

[Curiousyellow71]

It may be winding up the springs. It is a back pedal fest trying to get it hooked up with radials....more so then the other cars I have. I don't think it lifts the back much if it all. Front is a different story...once it hooks up. I have the car apart right now putting a 9 1/2 dynamic torque converter in. I think they said it would stall about 3800-4200. I think we would be much happier with new springs. I have read some people say getting a new springs with the perfect ride height is a challenge. I can fit a 10.5 x30.5 tire now... so I can do any ride height I want.... but I don't want it to sag....nor do I have time to switch them if the new springs suck. I don't think new springs will fix the sway feeling. But the car would be safer and hook up better.
Thanks for the input! I just happened to drive by the farm today where we bought this car in 1987. That brought back some memories!

 

[SureGrip]

The car squats so much I think the stock pinion snubber hits.

Mopars normally don't "squat", the rear of the car lifts. If the snubber is hitting the floor pan you may need a different pair of leaf springs, too much axle wrap up. IMHO[/QUOTE]
This was my thought too.

The rear should lift at launch or stay flat. What size leaf springs are in the back? Was this a 318 car that now is trying to handle a race engine?

I'd suggest a set of Mopar SS springs.

 

[miller]

Yep. Back when I had it, 63 Golden Commando Sport Fury ragtop, guys were quickly amazed at it. Yes, SS springs, snubber right, they told me the rear of the car would rise 5-6", on a hard launch...and just go...

 

[Curiousyellow71]

It was originally a 383 4v ac auto car. It has the bigger torsion bars in front. Not sure if the leaf springs are any different then a 318. The charger springs are not impressive probably what ever it was born with as standard equipment. SS springs I am concerned they may raise the rear 2 much...maybe need something done custom? It is a street car that will likely see the strip a couple times of year. Last time I crawled under the car I think i could see the pinion snubber has been hitting a lot. Not sure how much it really squats...front comes up at the same time. If I had it together I would go out and watch it... When we had 3.23's and a milder engine w stock converter it ran low 13's 108mph...60' times sucked 2.2 with radials. But no issues in the way it drove. Went straight didn't sway. Ever since we put more power in it with some gear...it's a handful. Now I am going to put a decent converter on top of that. I know the ss springs work good...concerned about the ride height.

 

[Ceedawg]

S/S springs, before you go racing again, do you have long rear shackles on this thing? Air shocks should never be on a race car (car will ride higher with S/S springs) 10,000 Mopars can’t be wrong.

 

[Curiousyellow71]

This is a street car. I barely have time to work on the car so I tolerated the air shocks to keep the car level till I get a chance to upgrade the springs.Tall shackles are hideous... thankfully we never got desperate enough to try that.
It won't go to the track with slicks with air shocks ever again. But I am pretty sure the springs are not why the car has a sway I think it is from the alignment getting affected when the front lifts. It drove ok until we started making hp. The espo springs may be a good compromise for the ride height I am after. I am guessing the ss springs will lift the car 2 or 3 inches more than level? Anyones experience would be helpful with the ss springs or espo springs and ride height of each. What to order for a 3700lb b body. Maybe I am kidding myself that the espo springs will handle 550hp and a 4000 stall.

 

[miller]

I am guessing the ss springs will lift the car 2 or 3 inches more than level?

Dang sure no expert here.
Can tell you, on SS springs, they were already on my first car, 63 Sport Fury. Have a set on my current 64 SF, bought years ago.
6 leaves on the left, 7 on the right. When first installed, yeah, sits at a little angle, but once things are seated in, levels out. To me, main thing is in the mounting. Stock hangers, front and rear, using an adjustable pinion snubber, to get about 1" clearance.
Whichever springs you get, make sure their the correct length, for the car/weight, that usually go together. Rear shackle angle correct, if that's the way you want to go.