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post #1 of (permalink) Old 01-21-2001, 11:53 PM Thread Starter
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Help understand CV driveshafts and pinion angle!

Okay, I know, I got lots of questions. I just posted about caster Anyway, I've been researching SOA conversion and am a bit confused. Why and how is a CV driveshaft better than a regular one. I thought I had this figured out, but am confused by this talk about pinion angle. Why does the pinion need to be rotated so it is pointing straight at the T/C if the CV will handle the different angles better? Is this a stupid question? Does anyone even understand? Am I just an insomniac that has nothing better to do than research SOA conversions? Hey, it's better than those damn info-mercials!!!!

"James and the Giant Jeep"
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post #2 of (permalink) Old 01-22-2001, 03:03 AM
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Re: Help understand CV driveshafts and pinion angle!

Check the tech section at http://www.4xshaft.com there is also a good article at http://www.outdoorwire.com/4x4/jeep/tech/shaft/

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post #3 of (permalink) Old 01-22-2001, 01:13 PM
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Re: Help understand CV driveshafts and pinion angle!

[img]/wwwthreads_images/icons/smile.gif[/img] Well, JAMMY........this topic has really been gone over a lot at different times, and basically here is the scoop: A driveshaft is a "System". It takes two u-joints to complete the system and for the joint angles to cancel each other out. For reasons which I will not go into detail on, if you have only ONE joint and it is on an angle, the power delivery is fast-slow-fast-slow-fast-slow. The shaft actually SLOWS DOWN and SPEEDS UP as the jopint goes through the 360 degrees of roatation. MAn has discovered that by putting a joint at each end, and phasing them correctly, that the joints would cancel each other and the vehicle would not KNOW that the shaft speed was not actually constant.....the yolks were, but the shaft WAS NOT. A CV joint IS constant velocity BECAUSE it is actually a short driveshaft, since it has two of everything, two yolks and two spiders. It is SELF-CANCELLING. So....taking what you know from the above, when you have a CV joint on one end, you can run the opposite end at ZERO ANGLE.....that is you point the yolk right at the t-case where the CV is.....because there is no need to help the CV cancel. The CV has angle, the rear joint does not. And because there is no angle, there is no fast-slow-fast-slow effect from the rear joint. Using a CV helps you get the pinion nose up off the deck and gives you one less angle to deal with and wear out joints.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #4 of (permalink) Old 01-22-2001, 01:42 PM
 
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Re: Help understand CV driveshafts and pinion angle!

As you read the tech section on Tom Woods page you should begin to understand the physics of a ujoint.

The answer your looking for here is the fact that a Constant Velocity or double cardon joint is comprised of two ujoints, which will cancel each others eliptical rotation. when adding a third ujoint to the equation (at the pinion end of your driveshift) It must be maintained at or near zero degrees or it will intrane vibration as it has no other ujoint to cancel its eliptical rotation. This why you need to rotate the pinion towards the T/C. Although it is actually towards the center of the second ujoint within your CV and not truley at the T/C that it should be pointed.
Is that as clear as mud? [img]/wwwthreads_images/icons/crazy.gif[/img]

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post #5 of (permalink) Old 01-22-2001, 03:46 PM Thread Starter
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Re: Help understand CV driveshafts and pinion angle!

I know this topic has been beat to death, it's just that when I search for it, it's hard to come up with good info. I now understand the principle of a driveshaft. I do have some questions though. What cancels the U-joint on the non-CV end of the driveshaft? And why not put CV joints at each end? If the yolk is pointed right at the T/C, then it's at zero angle. But what happens when it flexes or you hit a bump or something? What cancelled out the fast-slow-fast-slow? Now I've heard of lots of guys doing SOA's to their Jeeps and not pointing the front yolk towards the T/C. How do they get away with it?

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post #6 of (permalink) Old 01-22-2001, 03:55 PM
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Re: Help understand CV driveshafts and pinion angle!

[img]/wwwthreads_images/icons/smile.gif[/img] The u-joint on the non CV end is running at zero angle so there is no fast-slow-fast-slow created, since that is caused by ANGLE. What little off-zero angle you get when the springs move is insignificant since it usually occurrs at low RPM. There does need to be some calculating done to try and set the joint at zero when the Jeep is at hiway mode. Hiway loads and so forth on the springs. You ordinarily would not use two CV joints because you DON'T NEED TWO since the rear joint is a zero angle, if it wasn't for the movement of suspension you could connect with NO joint at all. If the pinion isn't pointing to the t-case, maybe they aren't running a CV on the t-case end?[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #7 of (permalink) Old 01-22-2001, 04:04 PM Thread Starter
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Re: Help understand CV driveshafts and pinion angle!

So what kind of calculations must be done to figure out the zero angle at hiway mode? And isn't there a chance of vibs from not getting the zero angle perfect. Is it even possible to get it perfect? Also, what about the front driveshaft? What type of driveshaft would I run if I did a SOA? This is just a thought, but couldn't you run CV joints on both ends of the front driveshaft and not worry about rotating the pinion up?

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post #8 of (permalink) Old 01-22-2001, 04:10 PM
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Re: Help understand CV driveshafts and pinion angle!

[img]/wwwthreads_images/icons/tongue.gif[/img] By calculations I mean determining the traveling height of the Jeep with the anticipated fuel load, gear, people, etc. You know, I have often wondered about why you never see two CV joints on the same shaft, and I don't know if they would even work or if the shaft would be too "floppy".[img]/wwwthreads_images/icons/tongue.gif[/img]

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post #9 of (permalink) Old 01-22-2001, 04:32 PM Thread Starter
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Re: Help understand CV driveshafts and pinion angle!

So do you have any opinions on what to do about my front driveshaft? I'm transplanting a set a GWaggy 44s into my YJ and am a bit confused about the front caster/pinion angle. Do I run a regular driveshaft or a CV up front? Do I try to adjust the pinion up a bit and let some positive caster suffer, or just let it be? Or should I cut the knuckles and rotate?

"James and the Giant Jeep"
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post #10 of (permalink) Old 01-22-2001, 06:02 PM
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Re: Help understand CV driveshafts and pinion angle!

[img]/wwwthreads_images/icons/smile.gif[/img] Grind out the welds and rotate the knuckles. That's the right thing to do.[img]/wwwthreads_images/icons/crazy.gif[/img]

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