Hi everyone. I thought I had my bump steer/death wobble problem fixed. The steering was good for a very long time. Today, I took my '56 gasser out for a ride for about 20 miles. Again no problem until I came to a stop sign and had to make a hard left turn onto the road I live on. Made the turn and started up the road. Was going about 20-25mph and OMG, the death wobble started all over again. I didn't hit any bumps or holes. I couldn't believe it. Thank God I was only a couple hundred feet from home and I was able to back it down the driveway. I looked underneath and didn't s anything of interest. I don't have a clue as to why this happened. Had the car up to 60-70 mph several times without a problem. It tracked very straight. During travel, hit minor bumps but still no problem. I also made other hard left and right turns with no problem. I might also add, that the stock steering box on this car is shot. There is absolutely no adjustment left. You have to constantly correct the car going around even slight turns. By correcting, I mean turning the steering wheel a decent distance. Any ideas why this suddenly happened?? Would this bad steering box cause this or at least contribute to it?? I'm open to any and all suggestions. Thank you, Carmine.
Bump steer/death wobble
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Carmine2
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If the chassis was level when you welded it and you measured the caster then, and when the wheels and tires are on it and it sits up in the front like most straight axle cars do, could that account for the additional caster?
I don't think the drive train weight is an issue.
I don't think the drive train weight is an issue.
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Look at the second picture in your first group of pics, There is something going on with your right front spring and it is not good. Are your u-bolts and spring center bolt tight? The leafs should not be splayed out like that. It is hard to tell from your pictures but it almost looks like the springs are a bit too narrow for those u-bolts in which case the leafs should have a band on them.
Just thinking about the lack of band on the spring, I don't think that's the real problem, but it may contribute. All the vibration isn't helping the leafs stay aligned without bands on them though.
I see now how you fixed the bump steer. Looks like you got that part right.
The one thing I see that I'd be thinking about is that long arm between the steering knuckle and the short link from the pitman arm. I see a couple of things there. First is that since it's made from a flat bar and it's pretty long, it may have a resonance and it's vibrating up and down at some road speeds. Excited by either the road or by whatever imbalance there is in your wheels/tires. The vibration would induce bump steer. If you would stiffen up that part by either making it thicker, or by adding a gusset or a pair of them at the steering knuckle, you may get some real improvement. The gusset(s) could make the flat bar into a T or C cross section. If you add gussets, make sure you extend it all the way to the knuckle, especially across the bend in it that's next to the knuckle.
The other half of your linkage problem is in the same area. You probably need a longer pitman arm and a shorter arm at the knuckle to increase the mechanical advantage. Your 18* caster isn't helping the steering effort either.
Just some thoughts, maybe some others can comment.
I see now how you fixed the bump steer. Looks like you got that part right.
The one thing I see that I'd be thinking about is that long arm between the steering knuckle and the short link from the pitman arm. I see a couple of things there. First is that since it's made from a flat bar and it's pretty long, it may have a resonance and it's vibrating up and down at some road speeds. Excited by either the road or by whatever imbalance there is in your wheels/tires. The vibration would induce bump steer. If you would stiffen up that part by either making it thicker, or by adding a gusset or a pair of them at the steering knuckle, you may get some real improvement. The gusset(s) could make the flat bar into a T or C cross section. If you add gussets, make sure you extend it all the way to the knuckle, especially across the bend in it that's next to the knuckle.
The other half of your linkage problem is in the same area. You probably need a longer pitman arm and a shorter arm at the knuckle to increase the mechanical advantage. Your 18* caster isn't helping the steering effort either.
Just some thoughts, maybe some others can comment.
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Carmine, In an earlier post you said that you had to turn the wheel alot before the car actually reacted and turned? If it has that much "slop" in the box, I would replace it before you do anything else. Excessive camber will magnify the problem. Just my take on it. /al
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shackles at the FRONT ??
Just going back over some of the straight-axle cars we've had in our shop , and the gassers we've raced , the light just came on . Not one of those cars was built like yours . We've always put the shackle to the REAR of the leaf-springs , so the axle never changes position for/aft . When your front-shackle axle sees a bump in the road . the whole axle can move to the bump . I see another problem when rubber bushings are used on leaf springs on a steering axle ; it's one more slight deflection the steering doesn't need . More "bump-steer" is caused by the soft bushings in the spring-eyes they're in there for the soft ride ; not something you need in a straight-axle car . Just another set of eyes ... Be safe...Bob.
Just going back over some of the straight-axle cars we've had in our shop , and the gassers we've raced , the light just came on . Not one of those cars was built like yours . We've always put the shackle to the REAR of the leaf-springs , so the axle never changes position for/aft . When your front-shackle axle sees a bump in the road . the whole axle can move to the bump . I see another problem when rubber bushings are used on leaf springs on a steering axle ; it's one more slight deflection the steering doesn't need . More "bump-steer" is caused by the soft bushings in the spring-eyes they're in there for the soft ride ; not something you need in a straight-axle car . Just another set of eyes ... Be safe...Bob.
1956 210 2dr. Sedan, 283, TKX, 9”, yup still working on it.
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Short of rebuilding the whole thing, I see two things to fix.
1. Caster readjustment, with shims.
2. And this is more work, run the drag link to the passenger side spindle. Yes, you are gonna hafta change the oil pan.
After that, clamp/band the leaves, tighten/check nuts and bolts.
I do agree about the shackles in the rear, but that is not a "deal breaker", lots of cars and ALL stock chevy pickups are the way your car is now.
1. Caster readjustment, with shims.
2. And this is more work, run the drag link to the passenger side spindle. Yes, you are gonna hafta change the oil pan.
After that, clamp/band the leaves, tighten/check nuts and bolts.
I do agree about the shackles in the rear, but that is not a "deal breaker", lots of cars and ALL stock chevy pickups are the way your car is now.
Thinking about this some more.
It seems to me that it doesn't really matter whether the shackle is at the front or rear with this setup. The axle itself is going to move in an arc when it moves up or down, with the arc center at the fixed eye of the spring. With the fixed end at the rear, the axle will move toward the rear as the suspension moves. With it at the front, the axle moves to the front as the suspension moves. If the distance from the fixed end to the axle is the same in both cases, the amount of movement front to back is the same in either case, just in opposite directions. If the axle is not mounted at the center of the spring, the short end should be the one that's fixed, i.e., no shackle.
I misspoke earlier, there IS a lot of bump steer with this setup, because the link from the pitman arm to the steering knuckle lever is so short. Leveling it just made it act the same way whether the suspension movement is up or down. That's why cross steer will work better, the longer link means less unwanted lateral motion as the suspension goes through its travel.
It seems to me that it doesn't really matter whether the shackle is at the front or rear with this setup. The axle itself is going to move in an arc when it moves up or down, with the arc center at the fixed eye of the spring. With the fixed end at the rear, the axle will move toward the rear as the suspension moves. With it at the front, the axle moves to the front as the suspension moves. If the distance from the fixed end to the axle is the same in both cases, the amount of movement front to back is the same in either case, just in opposite directions. If the axle is not mounted at the center of the spring, the short end should be the one that's fixed, i.e., no shackle.
I misspoke earlier, there IS a lot of bump steer with this setup, because the link from the pitman arm to the steering knuckle lever is so short. Leveling it just made it act the same way whether the suspension movement is up or down. That's why cross steer will work better, the longer link means less unwanted lateral motion as the suspension goes through its travel.
Carmine,
I agree with changing the steering box first and see how it performs. Then, with the car static, I would have someone watch for any deflection in either the steering arm or pitman arm with you turning the steering wheel side to side. As someone else mentioned, you may need to gusset one or both. There is nothing wrong with installing the shackle links to the front. GM engineers designed their staight axle pickups for many years that way without this issue. And you do not have to have "Cross Steer" linkage to eliminate this problem. I run the same steering setup as you without a wobble issue. Please keep us posted.
I agree with changing the steering box first and see how it performs. Then, with the car static, I would have someone watch for any deflection in either the steering arm or pitman arm with you turning the steering wheel side to side. As someone else mentioned, you may need to gusset one or both. There is nothing wrong with installing the shackle links to the front. GM engineers designed their staight axle pickups for many years that way without this issue. And you do not have to have "Cross Steer" linkage to eliminate this problem. I run the same steering setup as you without a wobble issue. Please keep us posted.
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Shackles should ALWAYS be on the opposite side the axle steers on. If the drag link is in front of the axle, then the shackles should be in the rear, and vice versa. Chrysler found this out the hard way with their Jeep Cherokee when they steered their axles on the same side as the shackles, and the steering pushed the axle side to side with shackle flex. Their cure was a recall that involved changing the shackles to the opposite side, and cured their problem with steering issues.
The big problem I see with Carmine's setup is the sloppy steering box, and that driver's side drag link connection! The drag link really needs to be relocated to the passenger side, so it will work properly. The short length will always emphasize and exaggerate whatever other problems exist. I know this is a huge deal to change, but it will make your car steer and handle so much better!
I also haven't seen any mention of what you set your toe in at? Straight axles should always have 1/8"-1/4" toe in, and if you have less it will add to the death wobble issues. Get a measurement on the front and rear of your wheels/tires, and make sure you've got the proper toe in.
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Chevy trucks, or any vehicle that has push/pull draglinks, are different. A push/pull steering setup doesn't care which side the shackle is mounted, as it wont deflect the axle while steering.
Thank you
First, I'd like to thank everyone for their continued responses. I really do appreciate everyones time. effort and suggestions. I received many more then I thought I would. Definitely alot to think about. What a great group of folks. Thank you very much, one and all.
Re. cross steering, I originally had it this way with a 14" fabricated pitman arm to be able to connect with the center link and then to the passenger side steering arm. I did it this way because of the oil pan being in the way big time and from what I read, it would give the least amount of bump steer. Someone said it would steer like a Mack truck and they didn't lie. It also gave me a severe case of death wobble at about 40 mph. So I changed it to traditional steering. I might add that I also looked at some different configurations of oil pans, but just don't know how I could ever make them work. The motor sits forward maybe 2" which doesn't help with steering alignment.
With the traditional steering, I went with a stock pitman arm, used a tierod end to connect to the driverside steering arm which is mounted on top of the spindle. The steering arm, as did the rest of the straight axle parts, came from Speedway as a kit. Part of the steering arm was fabricated to be able to reach, height and length wise, the tierod end. The steering arm is 3/8" thick and I used 1/2" flat steel for what I needed additionally to make it work. I did the measuring but I had it professionally welded. It does have a gusset welded in. I don't believe this is flexing, but I will certainly check into it.
I was out in the garage the better part of the day, just kind of looking things over. I took off the driver side wheel to get some better pics of what I mentioned in this tread. I will post them later this evening. Not sure why, but I gave a tug on the tierod end. This was kind of loose/sloppy. At first, I thought it was maybe the Heim hardware that was allowing this. A few more tugs and I saw that the steering arm attached to the spindle was loose. OMG. I could actually slide this a bit. Here I go again, but I could have sworn that I had all this tight. I don't have a clue as to how it loosened but it did. Tightened this arm and also the bottom one which also required some attention. Went to the other side and everything was good there.
I know that the steering has some issues, but not having the simple,
basics done proper, only adds to my problems. I'm going to go over all the nuts/bolts again, change the gearbox and try to reduce the caster. A friend is using my lift, so it's back to my roots: floor jack and cardboard.
As I mentioned previously, I will post some additional pics this evening. Kindly take a look. Maybe something additional will appear. Again, many thanx, Carmine.
First, I'd like to thank everyone for their continued responses. I really do appreciate everyones time. effort and suggestions. I received many more then I thought I would. Definitely alot to think about. What a great group of folks. Thank you very much, one and all.
Re. cross steering, I originally had it this way with a 14" fabricated pitman arm to be able to connect with the center link and then to the passenger side steering arm. I did it this way because of the oil pan being in the way big time and from what I read, it would give the least amount of bump steer. Someone said it would steer like a Mack truck and they didn't lie. It also gave me a severe case of death wobble at about 40 mph. So I changed it to traditional steering. I might add that I also looked at some different configurations of oil pans, but just don't know how I could ever make them work. The motor sits forward maybe 2" which doesn't help with steering alignment.
With the traditional steering, I went with a stock pitman arm, used a tierod end to connect to the driverside steering arm which is mounted on top of the spindle. The steering arm, as did the rest of the straight axle parts, came from Speedway as a kit. Part of the steering arm was fabricated to be able to reach, height and length wise, the tierod end. The steering arm is 3/8" thick and I used 1/2" flat steel for what I needed additionally to make it work. I did the measuring but I had it professionally welded. It does have a gusset welded in. I don't believe this is flexing, but I will certainly check into it.
I was out in the garage the better part of the day, just kind of looking things over. I took off the driver side wheel to get some better pics of what I mentioned in this tread. I will post them later this evening. Not sure why, but I gave a tug on the tierod end. This was kind of loose/sloppy. At first, I thought it was maybe the Heim hardware that was allowing this. A few more tugs and I saw that the steering arm attached to the spindle was loose. OMG. I could actually slide this a bit. Here I go again, but I could have sworn that I had all this tight. I don't have a clue as to how it loosened but it did. Tightened this arm and also the bottom one which also required some attention. Went to the other side and everything was good there.
I know that the steering has some issues, but not having the simple,
basics done proper, only adds to my problems. I'm going to go over all the nuts/bolts again, change the gearbox and try to reduce the caster. A friend is using my lift, so it's back to my roots: floor jack and cardboard.
As I mentioned previously, I will post some additional pics this evening. Kindly take a look. Maybe something additional will appear. Again, many thanx, Carmine.
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Probably just got loose from the constant back and forth motion of driving the car. I have had all sorts of bolts and nuts work loose on builds, and usually not critical parts.
I would suggest that anything critical should be assembled with Loctite Blue, even if you use lock washers, or nylock nuts. This is my preferred method, and I use Loctite in conjunction with lockwashers on all steering components that don't have castle nuts and cotter pins. I use it on anything else that works loose, before I tighten it back down, to prevent further issues.
I would suggest that anything critical should be assembled with Loctite Blue, even if you use lock washers, or nylock nuts. This is my preferred method, and I use Loctite in conjunction with lockwashers on all steering components that don't have castle nuts and cotter pins. I use it on anything else that works loose, before I tighten it back down, to prevent further issues.
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There's a lot of good info here from some very knowledgeable guys. I've never had, and always wanted to have an axled tri5.
My only experience with them was when I was kid getting able to steer gassers back to the pits behind tow cars. At certain speeds the wheel wanted to rip itself outa my hands! I asked the older guys about that, after they laughed at me I was told what everyone here already knows about, toe-in. At the track they didn't want the extra resistance of having the tires turned in so they'd run the tires straight, which of course caused the wobble.
I also got to pump the front tires up pretty high. I learned it would decrease their times slightly, and was told it would help with the wobble too.
I was about 15-16 yrs old at the time and got to do alot of grunt work which taught me a bunch.
My only experience with them was when I was kid getting able to steer gassers back to the pits behind tow cars. At certain speeds the wheel wanted to rip itself outa my hands! I asked the older guys about that, after they laughed at me I was told what everyone here already knows about, toe-in. At the track they didn't want the extra resistance of having the tires turned in so they'd run the tires straight, which of course caused the wobble.
I also got to pump the front tires up pretty high. I learned it would decrease their times slightly, and was told it would help with the wobble too.
I was about 15-16 yrs old at the time and got to do alot of grunt work which taught me a bunch.
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