1970 Dart Manual Steering-Car jerks left and right when trying to drive straight...

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KelPort

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Hi All,
Was wondering if anyone had any insight into a problem I'm having with my 1970 Dart Swinger. I just got the car back after selling it 10 years ago and I went to take if for a drive and there is something seriously wrong with the steering. When you're trying to drive straight the car will violently jerk left and right without moving the wheel, the fastest I dared to go was about 60km/hr. When you're in a corner turning either way it seems ok it doesn't jerk. But when you return to centre it feels like there's no load on the steering wheel and the car wants to jerk around. It's a 360, 727, 8 3/4 car with manual steering manual drum brakes. When I owned the car the steering was great for what it was, I was running 14" steels with 205 tires. Now one of the previous owners put 17" torque thrusts with 245/45s on it. The front tires are pretty shot but I don't think they're the real problem, I've never been geniunely scared of crashing trying to drive straight before, and I've driven some ropey stuff before. I'm thinking maybe the steering box is pooched, I've checked the toe and it's pretty close. Any help on where to start would be greatly appreciated, thanks
 
The front end could need a rebuild or some component of it could be bad...or it is the low profile tires, older cars often dart around badly once you switch over to a tire with a small side well especially on rutted pavement. Put some 15 inch wheels and tires on the front and see if it goes away.
 
Has the steering box been out or replaced?
I had the 4 mounting screws come loose in my Challenger when I swapped from power to manual and would do the same.
 
Broken lower control arm hole in K frame.
 
jos51700 said:
Broken lower control arm hole in K frame.
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Best answer
Also check the apron to firewall welds. Separation here allows the frame to be like Jello. The frame is connected to the steering arms which are connected to the tierods which are connected to the LBJs ,which control the steering.
 
67autocross said:
The front end could need a rebuild or some component of it could be bad...or it is the low profile tires, older cars often dart around badly once you switch over to a tire with a small side well especially on rutted pavement. Put some 15 inch wheels and tires on the front and see if it goes away.
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Has nothing to do with the sidewall. Nothing. Wide tires tend to "track" more than narrow tires, simply as a function of their width. A 245/60/15 would behave pretty much exactly the same regarding the "tracking" issue as a 245/45/17. The wider tire covers more area, and as such seeks out low spots/ruts in pavement more than narrower tires, they get drawn in to the lowest spot they come in contact with. So do narrower tires, but they cover less pavement. 245's aren't that wide, and even 275's don't cause what the being described. If they did the 275/35/18's on my Duster would be impossible to drive. I run 275's up front on both my Duster and my Challenger, have logged tens of thousands of miles on them between the two, and haven't had anything like what is described. They tend to follow grooves more frequently than narrow tires just because they're more likely to put some part of the tire over the screwed up pavement.

Something is in the steering or suspension is either very loose or broken.

jos51700 said:
Broken lower control arm hole in K frame.
Click to expand...

Very well could be.

AJ/FormS said:
Best answer
Also check the apron to firewall welds. Separation here allows the frame to be like Jello. The frame is connected to the steering arms which are connected to the tierods which are connected to the LBJs ,which control the steering.
Click to expand...

That too. Everything in the steering and suspension needs to be checked- tie rods, ball joints, idler and pitman arms, lower control arm pivots and mounts, UCA mounts, steering box bolts and even the steering box mount on the K frame. On my Duster the steering box mount welds were cracked, and the steering box would move around with steering inputs.

An incorrect alignment will worsen the problem (too little + caster) but based on the description of the problem I would say something is loose or broken. The steering box internals would also be the last thing I worried about, if the suspension and steering components are in good repair the car will not jerk about even if the box is worn internally.
 
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Anything that can wiggle, will.
Upper control arm mounts broken or loose bushings?
Not enough caster will result in squirrely tracking. Loose idler arm lets toe-in change with any suspension movement.
 
I have a truck that I have run with 295 tires on 20 inch rims and 295 tires on 15 inch rims on all four corners, on the 20 inch low profile tires the truck jerks all over the place, put the 15"s back on and it stops doing it... And nothing is even close to out of spec on the front end. You would not risk taking your hand off the steering wheel on the 20"s.....that's my experience yours may differ.
 
67autocross said:
I have a truck that I have run with 295 tires on 20 inch rims and 295 tires on 15 inch rims on all four corners, on the 20 inch low profile tires the truck jerks all over the place, put the 15"s back on and it stops doing it... And nothing is even close to out of spec on the front end. You would not risk taking your hand off the steering wheel on the 20"s.....that's my experience yours may differ.
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There's decades worth of Dodge Rams and diesel powered Ford trucks with "death wobbles" and steering geometry issues straight from the factory, all of them are "in spec". Maybe the big squishy sidewalls on the 295's for those 15" rims are masking your suspension or steering problem. Not to mention, how tall are those tires? I bet the 295's on 20" rims for your TRUCK have the same height sidewalls as most of the tires on 15" rims for these cars. But you didn't list the profile #'s so you're the only one that knows if you're making a fair comparison.

Sure, tires with shorter sidewalls will tend transmit more road noise/feel. And wider tires will track more than narrower tires, generally speaking. But regardless, changing from 15" rims to 17" rims should not cause your steering to "violently jerk", which is how the OP is describing his problem. That's not tires.
 
My truck is not the only vehicle that this happens to it was just the most extreme example of it in my personal cars, my wife has a Lexus GS that every spring when I take the 16" winter tires off and put the 18" low profiles which are the same overall height she mentions how bad it darts around on rough pavement.
I should have not used the term "in spec" to describe the suspension on the truck...it was 100% perfect.

Now I'm not really interest in going back and forth with you on tires and suspension, I just wanted to advise the original poster to try swapping over the front wheels and tires before he starts ripping the front end apart.

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......and the truck put down a faster lap time than one of the ZO6 Vettes that was racing that day....so by internet math 73-87 Chevy trucks are faster then ZO6's....
 
I had some 245/45-15 F-somethingorother on the front of my FormulaS one summer.The car cornered real nice with those.But the hunting was miserable. I was working as an alignment tech at the time, So I tried about everything imaginable to get rid of that.Those tires were pretty soft and they only lasted a few weeks. I replaced them with a new set of 235/60-14s. Problem solved. Same alignment.
 
AJ/FormS said:
I had some 245/45-15 F-somethingorother on the front of my FormulaS one summer.The car cornered real nice with those.But the hunting was miserable. I was working as an alignment tech at the time, So I tried about everything imaginable to get rid of that.Those tires were pretty soft and they only lasted a few weeks. I replaced them with a new set of 235/60-14s. Problem solved. Same alignment.
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I'm trying to keep 15" wheels and tires with at least a 50 series profile on my old cars for street use when I can....after wrecking two 19" forged wheels in the last few years I'm done. Winnipeg streets and low profile tires don't mix!
 
67autocross said:
I'm trying to keep 15" wheels and tires with at least a 50 series profile on my old cars for street use when I can....after wrecking two 19" forged wheels in the last few years I'm done. Winnipeg streets and low profile tires don't mix!
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I lost a couple of 15s there too, one with 275/50 on it and one with a 275/60. Stay outta St.James. Admittedly mostly my fault. I rarely go to Wpg anymore.
I prefer the ride of at least 50s. And they last a lot longer than "a few weeks"
 
67autocross said:
My truck is not the only vehicle that this happens to it was just the most extreme example of it in my personal cars, my wife has a Lexus GS that every spring when I take the 16" winter tires off and put the 18" low profiles which are the same overall height she mentions how bad it darts around on rough pavement.
I should have not used the term "in spec" to describe the suspension on the truck...it was 100% perfect.

Now I'm not really interest in going back and forth with you on tires and suspension, I just wanted to advise the original poster to try swapping over the front wheels and tires before he starts ripping the front end apart.
Click to expand...

Ok, so first, "darts around on rough pavement" and "violently jerks right or left" are two different issues. Yes, this is the internet, so we're stuck with personal descriptions that are completely subjective and descriptions that mean different things to different people, but if the OP is scared to drive the car because it's won't go in a straight line I seriously doubt it's a "low profile" tire problem. He described a car that is "violently" jerking one way or another while the steering wheel is held steady. There are millions of cars on the road with 17" or larger rims that don't have that issue.

As for the rest of it, by the logic you're using every car with rims that are 17" or larger must have this problem. Since that's obviously false, I really don't know what else to tell you. You prefer 15" rims, great, we get it. That doesn't mean that the source of every problem that occurs on a car with 17" rims is the fault of the larger rims.

As for swapping the rims and tires over, that will cost hundreds (if not thousands) of dollars unless the OP has another set of rims and tires that will fit his dart just sitting around. It costs nothing to look at the suspension and steering components to see if something is broken, or have a helper move the wheel back and forth while you check the movement of the steering and suspension components. Troubleshoot the problem, don't just arbitrarily throw parts at it. If the problem is really as bad as what the OP is describing, it should be pretty easy to pinpoint with a little troubleshooting.
 
My truck would jerk with the low profile tires, my wife's cars would dart..... And I never said it applies to every car on the road or every tire, but I have had similar problems with low profile tires.
I just assumed that most guys in the car hobby have extra wheels and tires or could borrow some to try...if it was my car the first thing I would do is try different wheels and tires if you don't spot some obvious front end problem.
Let's leave it at that and with any luck the OP will get it figured out.
 
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