U-joint on steering shaft: float or bolt down?

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Abodysrule

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I was wondering. Many on the forum love their U-joint (I have the Borgeson one), myself included. Pot coupler believers say U joints don't account for flex in the steering system as the pot couplers were designed to do.

So, question: why not allow the splines on the steering box end of the U joint to float, rather than tightening down the set screw? Just like a drive shaft yolk slides on the transmission output shaft to account for flex/angle change in the drivetrain, why not float the U-joint on the steering box shaft splines?

Brian
 
Because the U joint could "float" right off the steering box. The column is collapsible, unlike a driveshaft; and the length could change resulting in the column becoming disconnected from the steering box. There are supposedly plastic "shear pins" in the column to restrict movement, but how many of these are actually intact after all these years?
The pot coupler is actually to allow limited fore and aft movement of the column or box while still allowing flex during rotation of the column. Its this fore and aft movement that the U joint does not account for. Look at the length of the splines on a transmission/slip yoke and compare that to the steering box- nowhere near enough to be safe.
 
The column on the later cars is collapseable. Those of us with early cars die like men.
 
It’s a fail safe, kinda like a cotter pin. I’d use it.
RustyRatRod said:
The column on the later cars is collapseable. Those of us with early cars die like men.
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My 74 swinger is like a Volvo compared to my old Harley! Crash bars in the doors, padded dash, collapsable steering column, down right safe.
 
Abodysrule said:
I was wondering. Many on the forum love their U-joint (I have the Borgeson one), myself included. Pot coupler believers say U joints don't account for flex in the steering system as the pot couplers were designed to do.

So, question: why not allow the splines on the steering box end of the U joint to float, rather than tightening down the set screw? Just like a drive shaft yolk slides on the transmission output shaft to account for flex/angle change in the drivetrain, why not float the U-joint on the steering box shaft splines?

Brian
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Well my dad's 64 valiant coupler slipped off and he ended up in the ditch, upgraded to a ujoint tightened down and much safer.
 
thesiren74 said:
Newer style is slightly better but a ujoint is superior.
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Not in the early cars. The factory coupler is the only thing that allows any fore and aft movement. Replace it with a U joint and now you have no movement there at all and have extra vibration. No thanks.
 
RustyRatRod said:
Yeah? How about the MILLIONS that didn't fail? Junk? I don't think so. Neglected is more the likely scenario.
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Think what you want! It's always in the back of my mind seeing my dad's car in the ditch because of that contraption. Plus the benefit of header clearance seals the deal.
 
thesiren74 said:
Think what you want! It's always in the back of my mind seeing my dad's car in the ditch because of that contraption. Plus the benefit of header clearance seals the deal.
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I completely understand. That's not something I'd forget either.
 
Abodysrule said:
So, question: why not allow the splines on the steering box end of the U joint to float, rather than tightening down the set screw? Just like a drive shaft yolk slides on the transmission output shaft to account for flex/angle change in the drivetrain, why not float the U-joint on the steering box shaft splines
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What if it floats completely out?

Also the drive shaft has splins designed for the purpose. Whereas the steering shaft does not.
 
Not sure I agree with you on that. First, the steering shaft doesn't move up and down along its axis unless you crash and collapse it, the steering shaft is solidly fixed in place by virtue of the two snap rings and the upper shaft bearing. In the event of a crash and collapse, the column crumples and the shift tube (on column shift) and steering shaft collapse inside themselves telescopically; and they don't move away from the steering box, rather toward it. BTW, if your plastic sheer pins in your column are gone, you should not be driving the car. Mine is a '67 and they are in perfect condition.

Second, I don't believe the steering box/k-frame flexes sufficiently to pull the splines out of the U-joint. There is about 1 inch of the shaft's splines inside the U-joint. Is there really more than 1 inch of flex/movement along that axis? At most it might be measured in some fraction of an inch. Oh, I know, I'll clean out my old pot coupler and check the wear pattern of the shoes, that'll tell me how much play there was in my system at least. I welded and gusseted my K frame, use a Borgeson box and the Firm Feel sector support, so I would suspect there's less play in my system than factory setup.
 
BTW, this is just hypothetical, mine is secured on both ends as per instructions, I'm just asking for folks to share their thoughts.
 
The reason the factory coupler has some back and forth movement designed is because it is connecting two separate entities of the car together and must have some "give" designed in. It connects the k frame to the body of the car by means of the gear box. If the column was solid with like an aftermarket u-joint, there would be vibration transmitted where it was not designed.
 
Abodysrule said:
Not sure I agree with you on that. First, the steering shaft doesn't move up and down along its axis unless you crash and collapse it, the steering shaft is solidly fixed in place by virtue of the two snap rings and the upper shaft bearing. In the event of a crash and collapse, the column crumples and the shift tube (on column shift) and steering shaft collapse inside themselves telescopically; and they don't move away from the steering box, rather toward it. BTW, if your plastic sheer pins in your column are gone, you should not be driving the car. Mine is a '67 and they are in perfect condition.

Second, I don't believe the steering box/k-frame flexes sufficiently to pull the splines out of the U-joint. There is about 1 inch of the shaft's splines inside the U-joint. Is there really more than 1 inch of flex/movement along that axis? At most it might be measured in some fraction of an inch. Oh, I know, I'll clean out my old pot coupler and check the wear pattern of the shoes, that'll tell me how much play there was in my system at least. I welded and gusseted my K frame, use a Borgeson box and the Firm Feel sector support, so I would suspect there's less play in my system than factory setup.
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My thinking is it’s not designed to keep the shaft/coupler in place under normal driving conditions. I think that it’s for extreme chassis flex situations, like hitting a curb at speed/tire blow out. It’s that last little thing that might keep the wheel connected to the box when **** hits the fan.

I’m speaking of the bolt on the u-joint style coupler. Not speaking on the function of the original coupler.
 
OK, I have a data point. Luckily, my pot coupler was powder coated, so the wear pattern inside where the shoes rub was very easy to see/measure, all four tracks are 23 mm long. The edge of the shoe that rubs there is 21 mm long. 23 mm - 21 mm = 2 mm So, that means the flex my system was seeing at most 2mm up and down the steering axis (more likely 1 mm up and down from a central shoe position). No way those splines would pull out of the U-joint.

I'd be curious to see if anyone else has made this measurement and what the numbers look like.

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2.jpg
 
Abodysrule said:
OK, I have a data point. Luckily, my pot coupler was powder coated, so the wear pattern inside where the shoes rub was very easy to see/measure, all four tracks are 23 mm long. The edge of the shoe that rubs there is 21 mm long. 23 mm - 21 mm = 2 mm So, that means the flex my system was seeing at most 2mm up and down the steering axis (more likely 1 mm up and down from a central shoe position). No way those splines would pull out of the U-joint.

I'd be curious to see if anyone else has made this measurement and what the numbers look like.

View attachment 1716069960

View attachment 1716069961
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I can see the small hole in the coupler body where the small roll pin installs to keep the coupler from pulling apart. The early cars don't have that feature. But, it is also impossible for the coupler to pull apart in that fashion. I might could see the coupler sliding off the gear box, but it would have to have been either left loose, or not installed all the way or both.
 
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