Sorry, long post...

I was unable to find any forums that specifically deal with rack & pinion (R&P) steering so I am gonna spam this on all the car forums and pages I am a member of in hopes someone knowledgeable with Ackerman steering geometry and radius might be able to help me with what I thought was a simple steering solution. It still may be but maybe I have thought about it too much. Attached is a picture of the front axle setup for my 1958 Ford F100 pickup. The only difference of when this was taken and now is a disc brake conversion and shock mounts and it is on the truck.

So in a nutshell, I stuffed a big block Ford in the engine bay which left me no room to do the traditional manual steering box/power steering box swap that is common on these trucks. My options realistically (available room and available budget) are to leave the old sloppy manual steering or do an R&P conversion. They make bolt in systems but they will not work for me because I also did an axle over spring swap to lower the front stance. So I’m on my own to find a suitable R&P and make my own mounts. Not a problem for me. My issues are in the setup to make sure the Ackerman and toe in not affected when turning.

What I intend to do is replace the long tie rod that currently parallels the axle in a straight line from steering arm to steering arm with a R&P bolted to the axle. That way it moves up and down with the suspension eliminating any bumpsteer or toe in/toe out issues based on suspension travel up and down. I will use the stock steering arms mounted to the spindles and hopefully have enough room to mount the R&P so it is in a straight line between the two tie rod mounting holes. If there is not room, I will make sure the unit is parallel to the axle and the angles of the tie rods are the same.

With the stock suspension, when the wheels are turned full left then full right, the steering arms move in an arc and the tie rod stays parallel to the axle but moves closer to the axle as the turn becomes sharper keeping the distance between the steering arms constant. For example’s sake, let’s say it moves 2” closer to the axle.

My concern is when there is a full turn left or right, the R&P does not move but instead the outside ends of the tie rods on each side move forward towards the axle 2” while the inner end stays 2” away. So if you put the tips of your 2 pointer fingers together in a straight line and imagined that the knuckle where the fingers meet your hand are outer ends of the tie rods, you can visualize my example. With the fingers in a straight line. Move your hands out to create a V. Now the 2 outer ends are closer creating toe out or negative toe. I understand the length of the tie rods, the degree of arc created at the steering arms, and the distance they travel towards the axle will determine how much negative toe in is created.

So I think I have 2 questions. Any answers might create more though.

With a 51” overall length, is there going to be enough of a change to even notice or effect anything since sharp turns will be few and at slow speed compared to the majority of driving?

Is there a way to counteract this with vertical or horizontal angling of the tie rods (mounting the R&P higher and lower than the axle or closer to or farther from the axle)?

Any help would be greatly appreciated.

 

I got my answers. After I pulled the cab I took a good look at the front steering and how it moves. I was wrong to assume the tie rod running from steering arm to steering arm stays parallel to the axle and that the steering arms were at the middle of the arc at a straight ahead position. The Ackerman issue is addressed by the bends in the steering arms. As a result when the wheel is tuned hard left or hard right, one end moves closer to the axle while the other end moves away from the axle. Also, the inside wheel turns tighter than the outside wheel. So, I was right! I was over thinking the issue. A rack and pinion will work just fine.

 

Before I went the Jag front end, I did some research on an R&P for the straight axle that mounted to the axle itself. The most disturbing thing that I couldn't quite get over was the slip joint needed to handle suspension travel.

 

Have you looked at a high $$$ kit and see what they use? I'd bet there are off the shelf solutions but might be a combo of parts that they put together. I realize any place that markets the kit either wouldn't know or tell you where the parts are sourced from, but some measuring/comparing might tell you a lot especially as you have your head in it right now.

I see on your main thread that are looking at putting the original manual box back in -

 

Plans have changed. I'm not a kit guy or like the idea of non Ford parts in my Fords but the kit wins this time. Wife wants the truck done and it's my busy season at work. Ordering the R&P from Western Chassis. I called them and it uses a Ford Escort power rack and comes with everything I need. For $79 more I get the column saver kit.

Gonna hold on to the original for now in case my new project needs it. HAs low miles and is tight.

 

I know you're up against a time limit of sorts, so buying the kit is the best choice in this situation. I'll look forward to the progress in your main thread.