The Stovebolt Site Forums The Shop Area General Truck Talk Rack & Pinion w/straight axel????

Hi Everyone!

I've just finished looking through the old posts and a few websites and hoped to get a discussion going about peoples experiences and ideas regarding rack and pinion with a straight axel.

Here's the situation: I've got a stock front suspension (with lowered leafs and sway bar) and have been thinking about power steering. There are a couple of different ways to go about it, a new box using the stock steering components OR a power rack and pinion. Both options require borgenson joints etc...

So, I"m thinking a power rack and pinion would be easier than a reversed box, toyota box or box mounted on the outside of the frame requiring modifications of the steering arm.

The questions I've come up with are:

Mount the R&P to the frame or axel? If you mount to the axel, what factory applications had a slip joint in the steering column? (since I'll need to deal with axel travel)?

If the R&P is mounted to the frame, how could I reduce/eliminate bump steer?

Some threads talk about added unsprung weight if the R&P are mounted to the axel, but I'm not concerned with that as I don't think there'll be much weight difference compared to the stock steering components that I'll be removing.

Thanks for all your thoughts and input!

PS-

One of my other vehicles is a '93 Jeep Cherokee, which is four wheel drive and has a power rack and pinion mounted to the front axel. That makes me think that it is common on 4 wheel drive vehicles, and something that can be done on these trucks.

I guess one difference is that the Jeep has coil springs in the front, but I don't see how that changes things.

One of the basic principals of good ride and handling is to minimize unsprung weight. Since mounting the rack on the axle adds weight it just seems like the wrong move.

The only piece of the existing system that is both unsprung and removed in this conversion, is the tie-rod. I don't know what it weighs compared to the rack and pinion, but I'm sure it doesn't weigh as much.

If you read the other threads you know there is a kit to put a rack and pinion on the axle so someone has worked out the details and made it easy to do.

Old Sub-

I did read all the threads and saw the link and discussions regarding the NoLimitEngineering kit.

http://www.nolimit.net/index.asp?PageAction=Custom&ID=61

I also read the comments from several people mentioning that they had added rack and pinion to old rods they didn't have any more, or had friends who put rack and pinions in their rods 20+ years ago and havn't had a problem since.

No one said they'd done it to an AD truck. No one said which rack they used or what they did to deal with the Ackerman issue, or if there is one.
http://www.nationaltbucketalliance.com/tech_info/chassis/ackerman/Ackerman.asp

Some people commented that the Nolimit kit didn't look convincing, that the article discussing it mentioned that it didn't work so the authors actually used something different, etc...

Since I'm no expert I hoped to get some tips and input from ya'll who know to point me in the right direction so that when I figure it out myself I can avoid the pitfalls which are obvious to someone else but invisible to me right now.-

Like for example- you would need to change the steering arms because... or, a steering column slip joint at one end and borgensen joint at the base of the orignal column using a new bearing after you cut off the original steering box should get you there... or, the 19XX ABC rack would be easier to mount 'cause... or perhaps, 'when looking for a rack go for a short ratio one, like the xxx... or maybe 'you'll need a heavier duty rack given the weight of the vehicle, like the ones in the ABC trucks...

On the issue of additional unsprung weight- The R&P will weigh about 25 lbs. I think I'll have dropped 25 lbs between the centerlink, tie rod ends, drag link, and the conversion to disc brakes, modern rims, radial tires. And even if the conversion adds 5 or 10 pounds to the front end, I'll hope that won't make a noticble difference in the ride quality so much that I'll wish I had gone with a MII front clip.

Lots of guys have put rack and pinion on a Stovebolt, but most of them have done it as part of a Mustang II IFS conversion, which of course is an entirely different ball game.

I don't think you'll find a lot of people offering details on putting it on a straight axle, not because I don't like the idea, but because very few people have actually done it.

If Seon has you really should try to find him and ask about his experience.

If you choose wheels and tires with an eye toward saving some weight, I guess I'd believe you might be able to keep the unsprung no worse than where it started.

You might do a little experiment and add 25 poungs to the axle and then drive over some speed bumps and pot holes and then try a couple of the hardest corners you normally use, and decide if you find the ride acceptable. If so, then you're probably going to be fine.

I'm happy to engage in a dialog regarding the project, but I've not done it, and am not likely ever to try it myself...

I will offer one more opinion... Putting rack and pinion on the frame on a straight axle is going to create a serious bump steer problem.

Think about the movement of the tie rods as the axle moves up and down on each end. You'd need to mount the rack at the same height as the axle and even then I think it would bump steer pretty bad.

I recently ran across an article in "Custom Classic Trucks" February 2006 Volume 13 No.2 that shows an axle-mounted rack and pinion for Chevy straight axle trucks. The kit is offered by NO Limit Engineering (website nolimit.net) and has some good info and pictures outlining the procedure on an AD truck.

The conversion looks relatively simple, fairly rugged and could be a DIY project. My only concern would be in the transfer of road vibration through the column but I'm sure they have got that worked out.

BTW...the magazine is easy to spot as it has a blue/white Custom 65 F100 on the full cover. Check it out....

Dave

I could be very wrong, but I don't think there will be a bump steer problem if the R&P is mounted on the axel because it will move up and down on the same arc as the tires/axel do.

Bump steer usually occurs when the steering components don't move on the same arc as the tires/axel.

i drove a chevy oil truck in the early 70's that had some kind of power stearing cyl mounted on the straight axil. factory i think.
But my 2 cents, you will not efect the handling with a rack mounted to the solid axil.
your problem will be to get the steering wheel conected to the rack.
"i saw it on the web" some one some where makes a unit that has a gear and chain drive to get the alignment. it mounts on the fire wall and puts a shaft be low the headers and stuff.

Correct. That's why mounting a rack and pinion setup on the frame would be a bad idea on a straight axle truck.

Mounting it on the axle should avoid that issue, unless you introduce a problem in the slip joint arrangement.

NM51;
How is the rack connected to the column on your Jeep? Seems to me the big issue with hanging the rack on the axle would be connecting it to the steering column in a way that wouldn't bind or cause steering deflection on rough roads.
Speed

the rack has to be mounted to frame,,,rack has to be solid and non moving as it is coupled to the steer column and shaft,,tie rods take care of movment..a rack will work with a straight axel very well just install it correctly and you are in busniess..you will have to do home work as to the rack that fits your needs...doc

Doc I have to disagree with you.

There is a conversion kit that mounts a rack and pinion to the straight axle, and includes a solution that couples it to the steering column. Its been written up in at least one magazine, and I've seen it available for sale on the vendor's web site.

I'm not saying I think its a good idea, but the kit is out there and it appears to work.

I also don't see how you could mount a rack on the frame and not have a wicked bump steer problem, unless you mount the rack unconventionally, and use a drag link arrangement to only connect to one side, and then using a tie-rod as is common on these old trucks.

Otherwise what happens when you kit a bump with one front wheel and not the other? The two sides will be affected differently, and will turn different angles.

There is an article in Street Rodder magazine where a fellow has made up a rack that has a steering rod out of one side only. It bolts on the exact same mount plate as a Vega steering gear box but takes up less room. Of course the rod runs to the opposite side(cross steer) so bump steer isn't a factor with the straight axle. As I recall it isn't outrageously expensive. I think it was in the November 2005 issue but do recall it had a blue roadster on the cover and one of the cover feature stories was "putting a ford in a ford", which what I was doing at that time. I will look back through my mags and get an exact issue and page number. Second, a rack CAN be mounted to the axle since an axle only moves up and down, not forward to back or side to side. This only requires a slip joint and a u-joint in the steering shaft. As far as a solid mount is concerned, that I-beam axle is more solid than any frame rail.

This is an interesting one!
As has been said, the R&P will need to be able to travel in the same arc as the axle to avoid bump-steer.
It follows that with the R&P attached to the axle, a slip joint in the steering column will be required to allow for the movement of the axle.
A U/J of some sort willgive you this movement, would have to be heavy duty for a truck though?
As for a suitable R&P, get a tape measure and go to the breakers (salvage) yard. I personnaly don't like the idea of altering steering components, so I have always tried to match up lengths/dimensions etc with something that I can 'just bolt on'. Fabricating mounts/brackets is fairly straight forward, you just need to be sensible and bear in mind the weight of the truck and the forces involved.
Hope this helps
Taff

nm51 ,there is an install article for axle mounted rack and pinion on an ad truck in the april issue of truck builder magazine. there is also alot of illustrations and sources for the parts.

Found the rack article discussed above; it's in the Feb 04 Street Rodder, pages 119-123. It's called a Unisteer Unit. Looks like it should work. Made by Naval Manufacturing Inc, 800-338-9080 or www.navalgear.com

Just went to that site and got nothing but navy related stuff. Maybe phone number is good.

Coilover-

I Googled Unisteer and found on the website that its Mavalgear.com (M not N). They can make me a rack and pinion with the measurements I want (tie rod length, travel, etc...) but I didn't see a retrofit kit listed for straight axel.

Finding the right R&P is half the battle though! I'll call their techs and see what they have to say.

Update- I looked a little further on the website and found TWO (2) cross steer solid axle rack and pinion steering kits, one is for a 28-34 ford and the other is 34-40 ford. Both kits use a rack that mounts to one frame rail. They've got pictures of the two different kits. The 28-34 ford comes in two configs, one to replace a 'vega box' and the other for new build, which doesn't have holes drilled in the bracket. Price on these kits was about $350.

Definatley gonna call these guys and see what can do for an AD.

NM51,

I went through this same debate with myself over my solid-axle '59 Apache. I decided to reproduce the original GM power steering, optional on these trucks. This PS is a 'linkage' type that is 'added on' to the stock components. You can get new or used C-2 or C-3 Corvette components to duplicate the same setup. Mine works just fine.

If you mount a R&P to your axle, make sure you have the clearance between the steering column and the PS input as it moves up and down. The guys who tell you that a frame mount will produce 'bump-steer' are right.

You're going to have all manner of 'vibration feedback' with the R&P moving up and down with the axle using a slip-shaft to the steering column. Yeah, the wheels could just exactly cancel each other out as the axle moves, but that doesn't always happen.

Apache Kid-

Did your steering upgrade change the box to something that took less than 5 turns lock to lock?

The main reason I want to change my steering is to reduce the amount I've got to move the wheel to turn the vehicle. There aren't too many boxes, manual or power, that I've found that mount ontop of the frame rail with the pitman arm on the outside- Plus, R&P steering is just so much more tight and responsive than cross-steering.

NM51,
Obviously you're looking for 'quicker' steering. So was I. NOTE: Some folks don't like this idea -
I lengthened the pitman arm by an inch or so, which quickens the steering by that percentage (Do the math). I spliced two pitman arms together with the connecting mating area cut in a 'Vee' rather than straight across and had a really good welder weld the two together - resulting in a longer and therefore faster pitman arm. Since the steering effort is far less than stock, much less force is applied to the pitman arm since the power ram is doing most of the work. I repeat, mine works fine, and I didn't have to change out the steering box or steering column. I did have to weld on an attachment point for the power ram end to the cross-linkage (big deal). Somewhere in the bowels of my computer are photos of my power steering components. If you wish, I'll try to dig them up.

If you wish to see how the stock PS system was, have a look at:

http://chevy.tocmp.com/1955truck2shop/55ctsm0913.htm

Regards,