bump steer maddness

[guy858]

hi, I am having a terrible time with bump-steer on my 67 W200, front bushings are great, I have changed the front springs, but the ride height is pretty much the same. I have the factory manual steering, and I am running 33" 12.16.5's. the thing is almost uncontrollable when I go over bumps ! no play at all anywhere in the front end, tie-rods, knuckles, joints, wheel bearings,anything. alignment is right on ( level of course ) and I am running Monroe Gas Magnums. I can't be the only one who has this deliema ? I love the tank, but until I can figure out how to fix this, its more than work to control it when I hit a small bump, yet alone medium ones... I want to do some kind of P/S soon, but I would like to figure this out before I do that. I have got a Ford box and was looking to do something like the conversion to my stock steering configuration.. ( I saw it on the Heli something site awhile ago, and I know they had to quit making the kits, someone probably screwed it up and sued them ?? ) anyway, any help, I would more than LOVE it !!! been looking at a few bump-steer articles, but they are mostly for race cars and not my Power wagon.. thanks, Guy

[digdoug]

Are your new spring eyes orented the same as the old ones?If the camber is reduced ,steering gets loose...

[RussRoth]

Doug, I think you are talking about caster. I have air bags in the rear of mine and when I crank the back up several inches it becomes almost undriveable. All over the road.

Guy, are you really talking about bump steer or is it the dreaded Death Wobble? Sounds almost like DW when you are looking for loose parts. Mine is a '67 W200 also and has no bump steer and drives as good as just about anything I have ever owned. In fact, I wish my '01 Ram drove as well and it isn't too bad. Just not as well as the PW. Is your drag link level after the spring change?

[Boons]

Doug, I think you are talking about caster. I have air bags in the rear of mine and when I crank the back up several inches it becomes almost undriveable. All over the road.

Guy, are you really talking about bump steer or is it the dreaded Death Wobble? Sounds almost like DW when you are looking for loose parts. Mine is a '67 W200 also and has no bump steer and drives as good as just about anything I have ever owned. In fact, I wish my '01 Ram drove as well and it isn't too bad. Just not as well as the PW. Is your drag link level after the spring change?

Is your truck bone stock as far as suspension and Steering?

[jimmy]

My 69' drove great with 92' cummins springs, I just didn't like the ride. I picked up 78' w100 springs and the ride was way better but the bump steer was pretty bad- not uncontrollabe thou.
I removed a middle leaf from the cummins pack and re-installed. Truck rides a little better but no more bump steer. It's a happy medium.

I also notice when I put alot of air in my bags the truck drives worse. Level is ok and loaded with the rear down an inch or two it's perfect.

Keep in mind I have 92' dana 60 and springs up front and a 78-79 Ford power box ahead of the axle. My left front shock was relocated behind the axle to clear steering.


Make sure that you don't have a bad shock. Even if it comes to removing them and compressing them.

Let us know what you come up with.

[digdoug]

Doug, I think you are talking about caster. I have air bags in the rear of mine and when I crank the back up several inches it becomes almost undriveable. All over the road.

Guy, are you really talking about bump steer or is it the dreaded Death Wobble? Sounds almost like DW when you are looking for loose parts. Mine is a '67 W200 also and has no bump steer and drives as good as just about anything I have ever owned. In fact, I wish my '01 Ram drove as well and it isn't too bad. Just not as well as the PW. Is your drag link level after the spring change?

Thanks,Russ,I stand corrected.Darn brain farts anyways!

[RussRoth]

Doug, I think you are talking about caster. I have air bags in the rear of mine and when I crank the back up several inches it becomes almost undriveable. All over the road.

Guy, are you really talking about bump steer or is it the dreaded Death Wobble? Sounds almost like DW when you are looking for loose parts. Mine is a '67 W200 also and has no bump steer and drives as good as just about anything I have ever owned. In fact, I wish my '01 Ram drove as well and it isn't too bad. Just not as well as the PW. Is your drag link level after the spring change?

Thanks,Russ,I stand corrected.Darn brain farts anyways!

I have had my share of those.

[guy858]

Doug, I think you are talking about caster. I have air bags in the rear of mine and when I crank the back up several inches it becomes almost undriveable. All over the road.

Guy, are you really talking about bump steer or is it the dreaded Death Wobble? Sounds almost like DW when you are looking for loose parts. Mine is a '67 W200 also and has no bump steer and drives as good as just about anything I have ever owned. In fact, I wish my '01 Ram drove as well and it isn't too bad. Just not as well as the PW. Is your drag link level after the spring change?

hi guy's.. I love this site, been gone for a few days and didn't look here.. as for my springs, I got a set off another Dodge that had some more leafs in them, so I replaced the stock ones ( they had a few little pieces stacked at the bottom if I remember right, I got a good set of springs and put them on to try to stop this. ride height is really about the same. what do you define as death wobble ? the thing is perfect down a smooth asplalt road with no bumps, I know there is no play on the end joints, I shimmed them right when I had the front end off the truck and rebuilt it, ( *#%^, I had to order those things from Spicer and still have a bunch of them left, I had to order a whole box !!! ) knuckle is good also.. I will look at the drag link to check for it being level, I think it is pretty level ? as the springs didn't really lift the front end, heights really the same ? the shocks are old, but hardly any miles on them, I know that doesn't matter, I can pop them off easy enough.. I really appreciate all the help and advice from you guy's, great bunch. I've been a automotive mechanic for about 29 yrs, and this thing is driving me ( literally ) crazy !!! like alittle more info on " Death Wobble " to see ? I don't have any problems till I start hitting some bumps, the steering wheel kinda goes from side to side some.. thanks guy's

[RussRoth]

Since I had experience once with the DW I would have to say if you don't know what it is you have never experienced it. And I was only going about 20 MPH. Your wheels let loose and go into a shimmy/wobble that makes your rig uncontrollable. Normally your steering wheel will shimmy/jerk back and forth with some amount of force if you don't have PS and may some even with. The time it happened to me was on a semi and it was the drop axle that did the DW so I didn't feel it in the steering wheel but it shook the cab so hard I nearly cracked my head into the side window. There was absolutely NO mistaking what it was. I was looking in the mirror and watched it start. The tires started this real slow wobble back and forth, then all of a sudden just became a blur they wobbled so fast. I can't even imagine how bad it would have been @ 60 MPH on the freeway.

Your description does sound more like bump steer. Does it feel like a shimmy, like it's following the highway or steering itself? Does the steering wheel stop the side to side movement on it's own or do you have to slow or stop the rig?

I have essentially the same rig and mine drives really well. If I jack the rear air bags up too much the rig becomes almost uncontrollable at any kind of speed. Wants to follow every little groove or crack, darts all over and I can't maintain a straight line on the highway. It does that because raising the rear changes the caster to near zero and causes the rig to become unstable.

HTH

[elacruze]

Those big, wide tires need a lot more caster than stock.
These trucks have little caster to begin with-they were designed for narrow bias ply tires.
Radial tires tolerate and like more caster.
Big tires demand caster. I have a 1985 GMC K3500 with the same size tires-I set the caster at 4.5 degrees, and it doesn't wobble but it has absolutely no road feel. If I drove it a lot I'd go back and stick about 7* in it.

Find an alignment shop or auto parts that has caster wedges, and experiment with them. You don't really know where you are to start (unless the alignment you had done recorded caster) but either way your symptoms are common and point to inadequate or negative caster. Try a 4* shim, and work your way up until it stops improving. You can't hurt anything by adding caster, you will only make the steering more difficult.

Keep us posted.

[guy858]

ok... its definitely not death wobble.. god, what you described is EXACTLY what happened on a motorcycle I was riding when it got around 120 mph and went into a headshake.. I thought all life was over, handle bars just starting whipping from sise to side, I thought for sure I was going to be dead.. don't really remembver what happened ( it was a long time ago, I'm alot older now, don't do that *#%^ anymore !!! although I still ride a older Suzuki 1100 everyday ) but it quit shaking and I got control and remember having to wipe my pants !! anyway, the truck does straighten itself out by itself when the bumps stop, I'm pretty sure the drag link is pretty level, I looked today. I am in the process of building a pan-rod bar for the front end.. just because.. have built the bracket to mount it to the drivers side of the front diff. ( mounting it to the backside of the area between the spring mount and the knukcle ) going up to the frame on the right rail.. haven't made that one yet.. found a 1 1/8 center link from a Chev. Blazer, cut it to length and bought a 3/4 " heim joint and threaded the inside of the bar for the joint.. pretty much a straight shop to the frame, clears the headers and the pan, its mocked up, just haven't finished it yet.. I'll make sure the front end can't move at all side to side.... probably help the leaf spring bushings anyway ! I got a new digital camera for christmas, but haven't played with it much.. maybe take some pic's and post them ?.. the caster thing is interesting ? affects steering I know, doesn't affect tire wear.. caster is front to back in the wheel well. how do you change caster on this ? I guess I could measure and make sure its equal on both sides distance wise... we'll figure this out.. love the tank.. there's really not many of these around anymore, get looks when I drive it sometimes, its just a friggen handful !!!! to be continued....

[RussRoth]

If everything is truly tight as you say then it seems to me it can only be a caster issue unless toe could affect it. I sort of doubt it's toe though. Alignment shop should have some tapered wedges for adjustment. May have to go to big truck shop to find them.

[digdoug]

The point that I was driving at(before I screwed it up ) Is that the stock front spring eye is below the spring,and the rear spring eye is above the spring.ANY OTHER orientation will reduce caster.Clear as mud?

[pwadventurer]

Question, will adding more caster to reduce bump steer effect pinion angle?

[digdoug]

Question, will adding more caster to reduce bump steer effect pinion angle?

When you add caster to a drive axle it directly effects pinion angle.

What are you working on? The stock sweptline front axles don't really have any room for adjustment,as you may have noticed. A newer axle that is set up for power steering has a better pinion angle. It's just the way they are put together.

Why do you have bump steer? Are you running a lift In the front,rear,or both? Do you have power steering?

[pwadventurer]

I don't know if i have bump steer yet. I'm just preparing the front end and want to eliminate before it happens. I put a 60's era 4 x axle on my 70 dodge existing 2 x set of springs but i used the shims that came stock on the 2 x to match pinion angle with transfer case. I have the 4 x springs but they look like they are flat and don't give as much lift as the 2 x springs do. If required i can change out to the 4x springs. I also have proto techs power steering box and drag link back when they were making the set ups.

Rick

[digdoug]

It sounds like you will be fine.Its hard to tell for sure untill you drive it. You can do lots with a steering stabilizer and tire inflation if its a little darty. Just don't get the rear of the truck jacked up more than the front,and it should track good.

[elacruze]

Another question is what are you using for rims? If your rims have more than stock offset, your bump feedback will be amplified.

[Cageman]

bump steer means the link that runs from the steering box to the steering arm on the axle is running at an angle. If the truck is lifted a little bit, when the axle goes up towards the hood, the arm is held still by your hands and steers the wheels as it is in an arc. Im not good at explaining. at ride height the steering link needs to be level, or have a z in it that allows it to make the two mounts paralel. so it looks like this ---__ . If it looks like this / youll have bumpsteer