Hi Guys; I got a question regarding a 1956 f-100 with a straight
axle and Toyota power steering box.

What is BUMP STEER?
What causes BUMP STEER?
Does the power steering pump effect BUMP STEER?
How does BUMP STEER manifest itself thru steering wheel?

Thanks.
Gary

 

In a nutshell bumpsteer is caused by improperly designed steering geometry. As the front suspension goes over a bump (moves up and down) the toe-in can change and cause erratic changes in handling. The PS pump itself does not cause bumpsteer. It is caused by improper tie rod angle and length, camber, and steering arm pivot arc. I have owned vehicles in the past with bumpsteer and the usually the manifestation through the steering wheel is a movement back and forth as you go over the bump.

 

GreatNorthWoods; Vern, Thanks for your quick response. I just got my `56
running with new Toyota p/s. Seems to work fine but when I`m not moving
and turn steering wheel I get a sound like you get in a new car when you turn
all the way to the left or right (up against the stops). The pump noise lasts only
for a second or two. Wondering if it could be related to pump pressure or camber
(front end alignment)? Once into turn all seems fine.

Gary

 

When turning while standing still or at the turn limits the pump is pushing very high pressures, so noise might be expected. Be sure the drive belt is not slipping (shinny surface), and try not to turn while standing still. As GNW explained BS only occurs when going over a bump or in a high speed turn and is most apparent while going straight, the vehicle will suddenly pull to one side or the other.

 

If you have bump steer you would not be asking about how it feels. It gets to be scary stuff.

 

When at a standstill, there is more fluid being bypassed through a pressure relief valve that makes a "flow" noise.

But since this is a new install, I'm also guessing you may have some air still in the system. The usual procedure is to turn lock-to-lock slowly, and briefly hold at each end-stop (without pressure on the steering wheel), return to center, then shut off and let sit for a while. If you open the reservoir after doing this and the fluid looks sort of "shimmery", it is small air bubbles that are being purged from the box and hoses. May have to repeat until you don't see any more.

 

You will definitely feel bump steer. I have it now with my drop axle install. I set the toe in as close as possible and it eliminated quite a bit. I also installed my tie rod bar which had a steering dampener/ shock attached to it, which also helped. AX gave me some good info on the pitman arm and drag link, which you may want to check. The pitman arm is suppose to be straight up and down. The PO of my truck installed a steering box out of "who knows what type of vehicle?". The pitman arm is longer than the stock and the drag link is also longer than the stock unit. Therefore, my pitman arm is not straight up and down but faces to the rear. I still have full steering, but suspect this is contributing to my bump steer. You may want to exam your drag link as I did. Not sure what I'm going to do to fix the pitman arm and draglink yet? Could have a custom one made up, but that will be expensive. I may have to cut the drag link and shorten it up a bit. The pitman shaft is smaller than the original F100 pitman arm, so changing to the stock one isn't an option.

 

The pitman arm not vertical at straight ahead is a perfect recipe for bump steer and strange handling while traveling straight ahead. You really want to correct that geometry! Can you move the box back? I realize that will change the steering column angle some tho, do you have a tilt column?. How much too long is the drag link? what is the overall length? Is it a stock Ford draglink or has it been modified?

 

AX, thanks for the help. Won't be able to move the steering box as it's pretty much up to the firewall already. The draglink is about 2 inches too long and the pitman arm, I'm guessing is about the same length too long. The draglink is the same on the end that connects to the steering arm. The part that connects to the pitman arm is more like a tie rod end with the zerk fitting on one end and the nut with cotter key on the other. I could cut the draglink and reweld it up. In fact it appears that someone welded on it before. I have the original pitman and draglink that came with the axle, it won't fit on the pitman shaft of the steering box because it appears to be smaller. The original is 1.250 inches and the one on the truck is about .850 inches. I can't remember what position it was in with the other front end, but it did drive nice both on the street and highway.

 

Hey you guys; Thanks for the Info. Really help to eliminate some of the things I don`t
have to deal with. I`m going to have to check for belt slippage. I thought I purged
the system when I had the front wheels off the ground and turned steering wheel
from stop to stop several times. Maybe I didn`t do it enough or correctly.
Back to the work shop----!
Thanks again.

Gary

 

You could change the end on the pitman arm to a Ford ball if the pitman shaft is in the same original position on the frame then use a stock draglink, or modify it lke someone did for their manual Toyota box install (see the article on installing the Toyota box) using the spline section of the arm you have now. Easyest is likely to shorten the draglink just reinforce it with a pinned or plug welded sleeve over the splice and have it welded by a certified welder.

 

Hey Guys; A final report on Toyota p/s steering.

ALBQ F-1 -- I think you were right on. The first time I tried to bleed the air
out of the p/s box I must not have done a thorough Job. Re did it and no
more squeal. So thanks.

AX --- I also found the belt to be a little on the loose side, so that was tightened
(although I don't think there was any slippage). Just finished with the above
and took it for a test drive. It reacts just like like a new car - almost.

Thanks again everyone. Much Appreciated.

Gary

 

Alls well that ends well! (steers quicker too!)

 

It's good to hear good news.... I wish my truck reacted like a new car LOL.... Actually, I could be in Nascar, because my truck is all over the lanes. LOL.... OK, AX, we gotta get my front end together... I checked the pitman arm and it looks like it may be off of a 60 Ford F100????? With my wheel cocked all the way to the left, my pitman arm is straight up and down. I doesn't bind either way on turning. My guess is the previous owner took a draglink from a 60 F100, cut it and added the end from the 56 (with the ball end). My 56 pitman arm is only 3/4" shorter than the one on the truck. If I cut the drag link and shorten it, will it be too short or cause problems with the steering? Or, I could drive to NC and have AX fix it up for me. LOL....

 

So if you shorten the drag link so that the pitman arm is straight up and down ... will that make your steering geometry good as factory? Or is there more you have to do?