Technical HELP, car acts squirrelly when stomping throttle. Not good things. Something is wrong.

SYMPTOM: quick romp of throttle results in left rear dipping and right front coming up, just the opposite of what you might expect under sudden torque. Car drives well at all normal speeds. Crack the throttle, and things get real squirrelly and a bit scary feeling.

CAR: 55 Hardtop, all new front suspension, ride tech shockwaves front only (had same prob w prev suspension). Tried all diff adjusts w shocks. No diff. Front sway bar ( unhooking made no diff). New rear leaf springs (had same prob w prev set of springs). Mcgaughy traction bars (Added, made little diff). New KYB gas shocks mounted to upper shock bar (bar between frame rails. Approx 550hp 383 w manual trans. 4.88 posi.

Been ALL over the frame and suspension. Cannot find anything that hasn't been replaced and that is not in excellent condition. Checked ball joints, wheel bearings, tie rods, front/rear shock compression/rebound, springs, frame condition, body mounts, etc. all lol ok.

I used to feel very comfortable with this car at fairly high speed on twisters and off ramps. Right, now, something just doesn't feel right.

Checking each corner for compression and rebound with a hand to the fender and some aggressive bouncing and all feels excellent. Car lifts and depresses with authority and appropriate feedback. Take it for a drive and a quick crack of the throttle in second or third gear and you would swear it had a shot right front ball joint and cracked left rear leaf springs. Scary.

Sure would appreciate some thoughts...

 

LOL I had an OT 11 second streeter that did that when I first built the 4 link. I discovered that I had the links adjusted wrong?

My discovery is not going to be your probably no doubt but here is what we discovered, maybe it will give you something to think about. The driver side upper bar was too tight and putting the entire rear in a bind when I nailed it. We loosened everything readjusted for proper pinion angle and then when we nailed it, it would stand up and cut a straight line.

Anyway something to think about.

 

Thanks for the comments Pork. Something to think about for sure. I have had everything apart in the front end to clean and freshen the appearance. All seems free but it is likely worth loosening everything , letting it relax and snugging back up again. Probably the same in the rear.

I should also say I have driven this car w same power for maybe 1500-2000 miles in last years w no issues. Car started to feel squirrelly and I pulled it apart and found a damaged shockwave (no shock function, but air ride still worked). Ordered the upgraded style which is supposed to be more durable and put car back together. PS: it took me 5 years to get money together and get off my butt to do this. Installed new engine and converted Muncie to 5 spd OD at same time. Can't imagine that matters. Power output is similar.

Something def feels broken. I've been over the frame front and rear with a flashlight and cannot find any sign of stress, cracked metal or cracked paint.

Body mounts all good except for very last two at tail pan which are questionable. I replaced the outer tail pan years ago, but did not change the inner. I don't think they are any worse than they were when the car drove fine. Thinking of building some bracing and putting more significant mounts in this area. I know the hard tops and convertibles needed some extra mounts and were more prone to movement.

Not seeing body gaps moving around significantly (so far).

Pretty much afraid to drive it at the moment. I had a rear axle come completely out of a car once. Scary stuff.

 

You said you had a damaged shockwave and replaced it with an upgraded unit. Did you do both sides or just one? maybe its just the way I was reading it. Just a thought.

 

Are the front two Shockwaves connected together with a T fitting to a pair of valves or does each Shockwave have its own pair of valves.

 

Just my weird way of thinking but with 550HP and you mash the loud pedal somethings seriously wrong if it doesn't get squirrely . HRP

 

Worn clutches in posi making it one wheel drive?

 

Borrow a Go Pro hang it under the car and see what is going on.

 

measure the wheel base and see if both sides are the same

 

Thought about the gopro. May still do that.

Both shockwaves are upgraded to the newest style with 26 way (or something like that) rebound control. Have tried them set at both extremes and in the middle. No difference.

Yes, the line is a "T" to both front shocks. Hmm. Interesting. You would think if the left front twisted up, the last thing that would happen is the right front going higher yet. I could easily throw some shrader valves on it and see if that makes a diff. I'll try that and go for a spin.

And yes, the power can make things get crazy but I am not talking about hammering it and staying in it. Just a quick "Womp" throttle slap at a 30 mph roll in 2nd or 3rd gear. Scary. Not in a good way.

Car did not do this before. It would either spin the tires or the whole front would jump pretty consistent (especially with the large front stabilizer bar).

PS Rear axle is an 8.5" 10 bolt with 4.88 gears and factory posi. Seems ok. Been working ok for several years. I have recently inspected the internals added fresh fluid, posi additive and go.

 

Manyolcars, I am wondering about that too. Wheelbase... And whether frame has started to become a diamond.

Additional info... The car just has 17x8 Bf Goodrich street radials, NOT D.O.T. stickies...

 

When you have a car with metal springs, each wheel has its own independent spring, not linked to the function of any other.

When you have an air bag (or a Shockwave) with a pair of valves per bag, each wheel has its own independent spring, not linked to the function of any other.

When you have an air bag (or a Shockwave) with a pair of valves controlling TWO bags, via a t-fitting, you do not have two separate springs, each controlling a wheel. You have one big air reservoir, and that is a problem.

What you may have happening is something I have observed is many cars where someone is running a setup like yours.

When you go around a corner, and the weight transfers to the outside wheels, there is nothing to stop that outside front bag from being compressed, forcing all of its air out, through the line, and into the bag on the inside front.

This functionally enhances body roll.

Under hard acceleration, it can have curious effects as well, as one bag can unload more than the other, and relieve the pressure on the other. Bam, crazy handling.

You do mention a large anti-sway bar. Carefully examine the links and make sure that they are properly attached, and functional. The bar will prevent much of this, but not all.

Try splitting the system, and see if that helps.

 

I think Gimpy is right on. The T in the air line is a problem. The front springs need to be independent of each other. As you found out, the rebound control on the shocks had little or no effect with your problem. All the rebound control does is determine how fast the shock extends after being compressed. Typically you want a faster rebound in the front and slower in the rear, so the steering tires maintain contact with the road profile, and the rear end doesn't "hop".

 

I agree guys and really appreciate the responses.

I didn't have any problem with the first set of Shockwaves which had a larger volume chamber on each. These new ones don't have the big donut style bladders, but rather are made more like an old fashioned air shock. Maybe the smaller chamber makes them more sensitive.

The sway bar has new urethane bushings tightened appropriately.

I will go for a ride soon with the lines split and see what happens.

Thanks gents.

 

When you switched to the Shockwaves with the sleeve style bag, versus the bellows style bag, you reduced the bag volume.

The smaller the bag, the more pressure it takes to keep the car at the same height as a larger bag.

Imagine for a moment that you have perfect balance. Stand on a basketball, and it will hold you up. Stand on a tennis ball, and you will squash it nearly flat. Each has the same inside pressure. If you wanted to stand on the tennis ball, you would have to increase its internal pressure dramatically. (Don't try this, you will break your neck.)

The overall effect twofold.

One, since the volume is smaller, it takes a much smaller volume of air to be sent out of one bag to make a big difference.

Two, since the pressure is higher, it takes a much smaller change in pressure differential between the bags to make a big difference.

Since the air line can only move so much air at once, with large bags, it takes more time to move enough volume to make a difference. With smaller bags, it does not take much volume, so it happens much faster.

 

How about the spring bushings in the rear leafs. Or spring mount you said traction bars helped my thinking something is moving under load and the rear axle is not staying square.

 

The only time I have ever seen the right front lift is when we first started adding antiroll bars to the rears, if you adjust them wrong and preload them it will make for some weird stuff. To adjust them proper you leave them loose and set the driver in the car and then attach the link bars, there can't be any tension (preload). You adjust them to 'neutral' with the driver, when you launch the forces act equal across the bar, the rear stays level and front tires rise equal.
How that applies to your car I can't say.
You added 'traction bars' and the problem was present both before and after? Are the like a 'cal track' and not fastened at the front, kinda float like so they don't bind up with the leaf spring?

 

I'm with gimpy on this one. I'm no chassis guy but this sounds right.
My second inclination would be loosened rivets in your cross members allowing excess frame twist.
Good luck, keep us posted.

 

Axle movement?

 

check for a broken spring center bolt on your rear leafs-sounds like something is letting the rear end to move ahead on one side during acceleration

 

I'm restoring a '30 Plymouth for a customer and when I pulled the rear end out and cleaned it up, the hole in the spring pad on one side was an oval, about twice as long as the original hole - it was worn that way, maybe from loose U-bolts. Don't think the 85 year old 4 cylinder applied much power to the rear, it just got worn like that over years of use.

 

I appreciate all the constructive comments.

Just split the front lines and went for a drive. Absolutely no difference without the T.

The rear pins on the leafs are perfect. In an effort to address this, I replaced the near new 4 leaf springs with a brand new set. Both fit extremely snug. Neither set of springs made any difference. There are four u-bolts, all properly torqued and snug.

Spring bushings were new PST polygraph its in both cases.

I'm not overly impressed with the traction bars. They are McGaughys. They look like the photo.

Front steering, a-arm bushings, ball joints, etc are all less than 1000 miles old. The bolts on the a-arms have all been checked.

The frame is original, cleaned and painted many years ago. Rivets are tight. No cracks I can see. It is a welded two piece seamed frame. There is a tubular crossmember for the trans and a tubular crossmember for the rear shocks. I have been all over the frame and can't find any stress marks or cracks in the paint.

Rear shocks are KYB gas and switching them side to side made no difference.

There is no rear sway bar. Front only. Drove car with and without sway bar. No difference.

I am beginning to wonder if there can be something wrong with one of the shockwaves. May try switching right for left to see what that does.

The car has good firm bounce compression at all 4 corners. It rides excellent, smooth and even. Jump on the throttle and the handling gets stupid fast. This is not a horsepower issue. I've been driving the car for a number of years with a 500 or so hp 358, a Rockcrusher 4 speed and 4.88 gears.

Something is happening and I need to find it before something breaks at speed!

I'll keep after it and let you know.

 

What's with the bolt that holds the front of the spring, above the traction bar bolt? It looks off center from the recess in the frame.

 

The only time I experienced something similar, was with a 70 Nova SS, 350, 4-speed, with a 12 bolt. The Positraction discs were worn. It was especially bad coming out of a corner on power, or maneuvering in tight quarters. it was like being in deep mud or on ice. With the rear end cover off, everything looked fine, but the rear end mechanic replaced the worn out parts, and it tracked true. Worth a "look"? I am Butch/56sedandelivery.

 

The photo is not my car. Can't answer the question about the bolt. Just an example of the bar type.

Yes, I suppose the rear end could be an issue. It does have some age and abuse on it and is likely the weakest link as far as new parts.

I don't see where that would cause the left rear of the car to dip and the right front to come up. Seems like even a single trac rear would cause the car to jump with normal front twist and torque (at least until a tire spins).

I did lay into it a bit going into second gear tonight and it seemed to pull posi and spin both tires without issue.

Something to think about though.

 

My first thought in reading through this thread was the time I tore a spring pad loose from the housing in my car. That thing drove all kinds of strange, but if you've switched rear springs I'd think you would have noticed that.

 

My race car went really crazy when it broke the weld holding the axle tube to the center housing. I couldn't tell by looking till I climbed under and saw the plug weld missing.

 

When my car did that the axle housing had broken right at the pumpkin. Had it welded - no problem.

 

I appreciate all of the comments. I did check for the axle twisting in the pumpkin and that is definitely not happening. The rear axle is definitely not moving around on the springs. All leaf bushings fresh and tight.

Maybe getting closer though. Went for a ride today with someone following and also watching both sides of the car.

I think we have two issues...

1. The rear posi is definitely showing somewhat worn clutches when jacked up and in gear. Not bad, but looser than they should be.

2. Under a "romp" or stab of the throttle, what we are seeing is a tendency for the right wheel to put down the bulk of the power and it is massively wrapping/wadding up the front of the leaf spring on that side.

The whole axle moves forward a fair distance and then over centers backwards when it springs back a ways before re-centering itself.

The result is a darting right turn under throttle and darting back when you let out.

This is a new set of springs, but not likely strong enough for this much power. Will play some games with the traction bar mounting points before considering some custom springs.

Stay tuned.

 

I wonder what would happen if you added another long leaf to the spring set and a spring clamp as close to the front eye as possible, may have already suggested good luck with this.