bumpsteer

[cantspel]

Has anyone fixed the bumpsteer problem that becomes inherent with the flipped front axle? Its been months ago since I've done mine and I still cant drive it. I've been all over the internet looking for answers, but nothing. Lots of information on toe changes over bumps, but nothing for push/pull on pitman that I have.
Basically I flipped the front axle. Truck goes straight down the road until I crest a hill. As front end rises, the truck goes left. When the front comes down, she goes hard right. Dangerous to drive. Wheel actually gets pulled out of my hand. But it tracks straight and true down a road with no hills.
After lowering, the drag link looked like the bottom pic. I was advised that the ends needed to be parallel to each other and the ground. So I modified the link to look like the upper pic. I then noticed that the box was not in the center of its travel when in the straight ahead position, so I lengthened the drag link to get it back.
NONE OF THESE THINGS HAS CHANGED THE BUMPSTEER AT ALL.
So now I'm being told to raise the box, so that the pitman and steering arm are parallel, and the drag link can be straight. It is also prefered if the drag pivot (pitman arm end), and the rear spring pivot are in line so they travel the same. None of these 2 are that way from the factory. I must note that this truck drove GREAT before lowering, and the ONLY problem now is the bumpsteer.
I'm not looking for anymore trial and error type fixes. I have a hard time believing I am the first to have this problem.
With the truck on the ground, I can push on the RF fender and nothing moves. If I push on the LF fender the steering wheel whips side to side inside the truck. I don't understand why having the pitman in line with the steering arm is any better than what I have now. The bounce in the front end will still cause a push pull on the pitman. I am lost.





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[digdoug]

Cantspel,

The reason you want the drag link flat,is to make for the least amount of pitman movement,when the axel moves up and down.Other cures will help,but not eliminate bumpsteer.You are right about what you need to do:raise the box,or lower the steering knuckle arm.

Doug

[MountainMoparRobin]

OK the drag link is the rod that goes across from one tierod end to the other tierod end, the pitman arm connects to the steering arm, thats the arm in the piture that is hitting and creating "bumpsteer".
The most obvious solution to stop the bump steer is to shorten the pitman arm take it to a machine shop or welders shop and have the pitman arm shortened so the steering arm (the one pictured with the huge bend in it) doesn't hit on the draglink(the long arm 58" long connecting the tierod ends) get you a new steering arm, you should need to shorten the pitman arm (connects to the steering gear box) about 1 1/2-2 inches which will get rid of the bumpsteer

[CLIFF]

Robin.....When I ordered my Steering Arm from RARE PARTS...."only place I could find it new!" Napa turned me on to them. It was called a Drag link. And they also sell the rod that the left and right tie rod ends go onto and its called a Tie rod in there catalog....Cliff

[fosh69]

I tend to agree with CLIFF on this one Robin... the tie rod would be the long one and the drag link is the one from the pitman to the knuckle.

Whatever movement occurs on the right front seems to be amplified due to the leverage: the tie rod is the only thing that connects the moving parts together from left to right. The tricky part is finding where the movement is binding enough to cause feedback to the steering gear. Original geometry allows the axle and tie rod to move together in unison no matter the suspension deflection. In essence, the drag link needs to be able to move through multiple situations without sending feedback through the steering gear. In order for this to happen, the knuckle drag link and gear have got to be in their original positions. There's a tolerance designed into this setup to account for a few inches here and there with different springs and such, but when you drastically change one components position, it will throw all the others off kilter. Bending the drag link like you did may work, but the distance from the pitman tot he knuckle has to stay the same as factory... as should the intended movement of the drag link joints.

Also, I forgot to mention the caster shims... did you have any? If not, all you have is the few degrees built into your axles, and if you changed it any when you welded on your spring perches, that will definitely affect the steering. I've read that 5-7 degrees is optimal, but I could be wrong.

[Hobcobble]

OK the drag link is the rod that goes across from one tierod end to the other tierod end, the pitman arm connects to the steering arm, thats the arm in the piture that is hitting and creating "bumpsteer".
The most obvious solution to stop the bump steer is to shorten the pitman arm take it to a machine shop or welders shop and have the pitman arm shortened so the steering arm (the one pictured with the huge bend in it) doesn't hit on the draglink(the long arm 58" long connecting the tierod ends) get you a new steering arm, you should need to shorten the pitman arm (connects to the steering gear box) about 1 1/2-2 inches which will get rid of the bumpsteer

Robin,
The modified part of Cantspel's steering set up is
the drag link.... part#1939-107, described as the
drag link right out of my Dodge Truck Parts Manual.
The steering gear arm is #1938-513, described as
such, or aka "pitman arm". The rod connecting each
steering knuckle arm is part #2228-599, described
as the tie rod. I'm posting this so everyyone who
chimes in to help is on the same page.
Hope this helps move things along.
John

[motomatt383]

i don't think shortening the pitman arm is an option. 1st off you'd need to be magilla the Gorilla to turn it in a parking lot, 2nd a shorter pitman arm won't have enuff front to back movement to turn the wheels very far in either direction.

unfortunately i don't have a cure either, short of relocating the box! and thats hardly an option. we've talked about doing rack & pinion deals this might be exactly way we need to figure that out for an option!

matt

[fosh69]

we've talked about doing rack & pinion deals this might be exactly way we need to figure that out for an option!

matt

the nolimit kit for ford and chevy straight axles was delayed for several months because of bumpsteer issues, I believe. The application for a dodge they wouldn't even consider at the time. Am I right in saying the dodge straight axle has a wider track width than the chevy and fords? Also, the kit is designed for early ford tie rod ends and knuckles (ball-type knuckle) which I'm sure could be swapped out for the style on our trucks. So aside from the tie rod ends and the shaft lengths, why couldn't these work? Perhaps the bumpsteer issue. The key would be to have the perfect position for the sliding shaft from the rack to the steering column... get that right and there should be little to no bumpsteer.

Another option if anyone wants to expand on is crossover steering... but that could get messy on a lowered truck.

[cantspel]

I'm not opposed to raising the box. If you look at the shield that surrounds the column where it comes thru the cab, it looks like you could move it out of the way, move the box up and drop the column. would have the make some box mounting brackets and possibly box the frame in that area, but it wouldn't be too bad. I just want to know if that will fix it, and why. I don't understand why the draglink doesn't just pivot on the ball joint in the pitman as the front end travels.
I guess as the steering arm comes up, the distance between it and the pitman wants to change, so it pushes and pulls on the pitman. But how would that relationship change by moving the pitman in line with the steering arm? And why does it work from the factory? Can someone post a pic of a stock arm, drag, and pitman with the suspension loaded and the wheels in the straight ahead position so we can compare where I started.

[digdoug]

cantspel,

To understand why the draglink must be flat,draw two lines on a piece of paper,one verticle and one intersecting it horizontally.The point they intercect represents your steering knuckle arm.The verticle line represents your axel. Now get a compass and draw arks vertically through that intersection, with the sharp end on the horisontal line.Open up the compass and draw several arks through the intercestion of the vert. and hor. lines,moving the point of the compass along the the horisontal line from point to point.These arks represent drag link lengths,and angles. As the ark moves away from the intersection,bumpsteer increases.

I hope this helps you visualize the dynamics of the situation.

It looks like a good tine to retro some power steering! The sky is the limmit. Hit the salvage yards,and look at different boxes that may work.

Doug

[MountainMoparRobin]

When you flipped the straight axle, you gained 2-3 inches on the arm (the one with the big curve in it) that 2-3 inches gained would be accomedated for by shortening the pitman arm 1 1/2 -2 inches, you don't loose any of the turn radius because you've gained it in another area, you could also shorten, and keep the steering arm straight as digdoug is telling ya, because you have to take out of the steering geometry the added drop inches of 3. you changed the geometry greatly so you have to change to the new geometry, either by shortening the pitman arm or steering arm (connects to drivers side hub) something has to get shorter to match the drop Good explanation fosh69, thats why something has to get shorter to accomidate for the added inches to the steering geometry when the axle was flipped

[MountainMoparRobin]

if you look at the first picture you can see where to take out the added inches, that is one of the best pictures to work this out, there is clearly too much length in what you are calling the drag link, that why to compensate for that the arm was bent to try and make shorter, even with that you can see its going to hit when turning, because also the pitman arm is too long, so even if you shorten the draglink it will still have to have a curve in it because the pitman arm is now so long when turning hard right it will still make the arm hit, so you will still need to shorten the pitman arm anyway what would you mount the steering gear box too??? then you would also have to relocated the steering wheel which would then lead to cab problems as far as seating, so why not just do it the easy way and shorten your pitman arm and what your calling the drag link????

[MountainMoparRobin]

Here is the Logic so you can make your decision on how to deal with the bumpsteer: As explained above these parts were designed to have a 3-4" inch flexibility for the depression of the springs, A few of you have talked with Eaton Springs, and The Drop axle bussiness and both have comfirmed that the maximum allowable drop with keeping all parts the same is 3", without changing the geometry of the suspension, so when you flip the axle your going at least 5" down, therefor the existing parts in the geometry have to be changed to accept the drop! preferrably by shortening both parts instantly affected by the drop (pitman arm-draglink, forum terminanology) so you could take 2" out of the drag link, and 1" off the pitman arm, thus reducing both parts it will compensate for the 5"+ inches of the drop and keeping the 3" flexibility of the suspension

[slick]

I could be wrong, but I think there are different length and different bent steering gear arms. I think the powerwagon ones and different size trucks have different ones, I would look into that as well to see if something would work. I know my D-200 has a different bend in it than the one in the pic. Maybe that would help? I would even consider trying to run an airbag set-up in the front like I was going to do. That way you could air it up when you were driving thus eliminating bumpsteer then let it down when you were just cruising or parked.

[RussRoth]

[quote="slick"]I could be wrong, but I think there are different length and different bent steering gear arms. I think the powerwagon ones and different size trucks have different ones, I would look into that as well to see if something would work. I know my D-200 has a different bend in it than the one in the pic. Maybe that would help?

That is true. I have had a couple D100's and the arms were longer on them than on my PW

[digdoug]

I could be wrong, but I think there are different length and different bent steering gear arms. I think the powerwagon ones and different size trucks have different ones, I would look into that as well to see if something would work. I know my D-200 has a different bend in it than the one in the pic. Maybe that would help?

That is true. I have had a couple D100's and the arms were longer on them than on my PW

Yep.The D100-200 uses a 7" pitman arm.The W100-200 uses a 6" arm.

[slick]

just to see a difference here's mine:

[cantspel]

I'm going to look @ it this weekend. Maybe I can split the difference between moving the box and shortening the pitman arm. I'll keep you posted as to how it works and more importantly, is it fixed.

[digdoug]

I ran across a loose W200 pitman arm in the shop today.It is acually 6 3/8" between hole centers.I also saw a bent arm like slick posted.It is off a D300 with power assist.It measured 8 1/4 between centers.I didn't see any D100-200 arms laying around to measure.

Doug

[MountainMoparRobin]

don't forget to try and get another drag link arm also for just as digdoug pointed out that arm needs to be as straight as possible, you could also just have your existing arm cut and welded!