The Stovebolt Site Forums The Shop Area The HiPo Shop Power rack on straight axle

Looking at the power rack and pinion for my 52 panel with stock axle, has some one installed - any information, Performance online have this set up:http://www.performanceonline.com/store/customer/product.php?productid=19675&cat=1338&page=1

Pat

you cant put a rack on a straight axle. The geometry wont work. you would have to mount the rack to the axle.

just get a power steering gear box and install.

Hi Scott,
Did you follow the link and look at the setup
and yes you do mount the rack to the axle.
Pat

Link doesn't work. Also, I'm with Scott, you can't mount a rack to a straight axle and have it be safe.

Sorry about the link. I wanted to know if anyone has seen one installed.
if you would like to look at the set up go to
www.performanceonline.com
Pat

Scott, why can't a rack and pinion be mounted to a straight axle? I'm a novice when it comes to steering geometry and am just curious why it wouldn't work. Would there be excessive bump steer? Thanks for any help here.

Connection to the steering column would be the big issue. There would have to be both a telecoping shaft as well as a couple of U joints to allow it to flex with the suspension, just like a driveshaft. That will make for very unstable steering input. On top of that, there's also the increased unsprung weight, very bad for suspension performance.
On the steering angles, unless that rack is set up to moove in 1 solid peice, with tie rods only where it attaches to the steering arms, there will be severe toe out on turn angle issues.

I think it was 5 years ago "No Limit Engineering" came up with a rack and pinion setup. I might be wrong, but you'd think someone has done thier homework and tested this modification out. Product liability would be first and foremost to the vender? The key is the sliding steering shaft. Also how much "unsprung" weight is the rack going to add? Last I would think any thing would be better than a worn out stock unit. Just my 2 cents.

Think about mounting the steering gear box to the axle and how you would mount the steering column to it. The axle moves up and down and slightly forward and backwards. The steering column is solid. The rack is the same way, do you really want your steering column to be that flexable?

Another problem is mounting the rack on the axle so the tie-rods are inline with the steering arms. This makes the rack hang off the rear of the axle 2" to 3".

Can you even get a straight shot from the column end to the rack?
What rack are you using?
Did it come off a heavy truck or some lite weight car?

A worn gear box is way easier to rebuild then all the custom work needed for a rack install.

Good luck with your quest!

Joe



Joe

No Limit Power Rack Conversion

regards,
Leon

we've covered this before a few times... try a search.
here's one result https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=541056#Post541056

Here's some info for those that think it's a good idea..
http://www.freightlinertrucks.com/trucks/featured-components/axles-suspension.aspx
I've got a picture of one from a trucking show a few years ago, let's see if I can find it.

I still don't think it's a smart thing to do.

Grigg

You would be surprised by how many vendors do not "do their homework" when they offer a product. As Bill and Grigg mentioned. It is not a good idea. Even unisteer has one, however its a single sided rack that mounts to the frame and still requires the tie-rod between the spindles. That would be my choice if you really want a rack on a straight axle. Then again, if I went with a straight axle, I would simply have bolted a power box to the frame and have been done.

Yes, todays modern Class 4 and larger vehicles have rack and pinion on larger Arvin Meritor and Eaton axles. Then again, the wheels and tires also way 300# each. While the geometry may be similar, the physics is different.

Yeah and both have to be right for the steering to work!

well if I see Freightliner has the same set-up I am going for it
will post photo and let you know if it work or not.
Pat

Just keep in mind, you will be adding 40 pounds of unsprung weight to the axle, plus a shakey at best steering input shaft, that will adversly afect the handling of the vehicle.

I know, have you looked at the web photo's.
I have a straight axle on one truck and a pacer on the the other panel what the hell, I will try anything
Pat

No,
Freightliner has a completely different setup, one designed from day one to bolt to the axle and a telescoping steering shaft also designed for the job.

You could try the Freightliner setup, may weigh as much as the whole axle does already....

The rack you're considering was originally stationary and bolted to the frame/crossmember, the steering shaft slip joint hardly ever moved.

Say it is mounted to the axle,
When you are steering hard one way and also go over a bump or dip how much does the telescoping shaft bind and push and pull on the pinion?
Do you think the pinion is anchored and supported well enough in that aluminum housing to take the abuse of pushing and pulling on it continually?
Will it give up and pull out or wear out seals quicker than desired?
Is it designed to take end thrust in both directions?
What if the telescoping shaft gets rusty or sticky, then how much force is applied to the pinion?

I don't have those answers but I'd sure get them before charging ahead.

Grigg

I have looked at the photos, still looks shakey to me. I also looked at the Freightliner setup. It appears to be for trucks with a setback axle, which makes the steering shaft a straight shot. I also noticed that they still have a conventional type steering system, so they have not adopted it across the board.
Should be noted, no light truck or passenger car has the steering gear mounted to the suspension/axle, they are all frame mounted.