Power steering to manual conversion (with pics)

[a70duster]

I have a '72 Duster that came with power steering. I'm currently putting a 383 in there and the power steering system occupies a lot of space. I chose to swap to a manual steering box. I did some research and only found some vague information. Here is the solution I came up with with the advice of others.

I purchases a 3/4" 36 spline to 3/4" hole steering u-joint. They're pretty easy to find on the internet, just pick your favorite flavor. There is about 1 1/2" gap between the steering shaft and the u-joint.

The steering rod needs to be extended about 1 1/2". There are a few ways to do this. After the rod is extended, you'll need to drill a 5/16" hole in the 3/4" part of the u-joint. Add a grade 8 bolt with a locknut on the other side.

This is a low cost solution that other have implemented.

 

[72bluNblu]

I have no doubt that other people have done this, but, it's not a good idea.

The original pin that goes through that steering shaft is hardened, and is a press fit with a particular tolerance to keep any play out of the system there.

Using a grade 8 bolt there absolutely will not give you the press fit that you need. The fact that you're using threaded bolt for that is a BIG issue, unless you're grade 8 bolt has the proper length shank so that there's no threads that are going inside that steering shaft bore. The lack of a press fit will mean play between the bolt and shaft, and that will wallow out the hole in the shaft and the play will get worse.

Even without that, there's a really good chance that pin has a higher toughness than a grade 8 bolt. Grade 8's are good for what they're supposed to do, but that's not what they're for at all.

And because you've gone round-round between the shaft and coupler, you're depending 100% on that bolt to retain steering.

The power steering and manual shafts were also not the same length, and the parts of each of them were not the same length. The manual steering shaft was not just a collapsed power steering shaft. So, you don't have the proper engagement if you just fractured the plastic holding the shaft at length and extended it.

You can use a "D" section and weld that onto the steering shaft, or, you should have used a mill or press to properly size a hole in the couple for a press in pin.

 

[a70duster]

I see some of your points. There is slop in the factory harded shaft to shoe and shoe to collar.

There are no threads in the bore of the shaft. With the bolt torqued there is no slop.

A welded-on shaft can fail. I do agree that if there was a double-D on the shaft that would keep the shaft from potentially turning in the u-joint hole.

How do you figure a grade-8 bolt breaking in this scenior? Seems highly unlikely.

 

[72bluNblu]

I see some of your points. There is slop in the factory harded shaft to shoe and shoe to collar.

The slop in the factory system is between the hardened pin and the shoes, which are replaceable. The slop is not between the pin and the shaft, which is where it will be with your arrangement, which will cause the steering shaft to wear. That's not what you want to wear out.

There are no threads in the bore of the shaft. With the bolt torqued there is no slop.

Well at least you didn't put any threads through the shaft. But the torque on the nut isn't going to prevent the bolt from wearing the shaft or the other way around. The force the bolt and shaft are exposed to is rotational, clamping it at the end with the nut doesn't stop that.

A welded-on shaft can fail. I do agree that if there was a double-D on the shaft that would keep the shaft from potentially turning in the u-joint hole.

Everything can fail. The factory shaft has a weld in it. If the weld is done properly it will not fail, and more importantly, there's no movement to create wear.

Round-to-round with an off the shelf bolt is just asking for a problem that doesn't have to be built into the system.

How do you figure a grade-8 bolt breaking in this scenior? Seems highly unlikely.

The same way the break in any other scenario. Grade 8 bolts are fairly "hard" as far as metal goes. They have a good tensile strength, but they can fracture, especially if there's a lot of load cycling. The edges of the hole will create a concentrated shear load on the bolt and with lots of load cycling, which you will get at that location, cracks can develop.

Having the bolt break is somewhat unlikely, the wear is going to be the larger issue and it will progress a lot faster than you think because none of those parts are designed to have movement there. But factory steering designs went to redundant systems that can't spin when they fail for a reason.

I have had grade 8 bolts fracture. For example, I used a grade 8 bolt to go from my clutch pedal to my hydraulic cylinder for my hydraulic clutch. It took years, but it did eventually crack. And for the same reason, lots of load cycling. Grade 8 bolts aren't indestructible, it's just a load classification that is VERY specific. When they get used in applications they weren't intended for (ie, replacing a hardened, press fit pin) they can fail much more quickly than you think.

This part right here exists exactly for all of the reasons I've explained, this is how you go from power to manual steering correctly (without changing the steering shaft out entirely at least).

 

[abodyjoe]

i used thes when i did it years ago. cut it to length and install. easy peasy.. probably still have the column shaft out in the shed somewhere with it on it.

FR1505M - Mopar Coupler Shaft Kit - Power to Manual





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