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Unread 11-19-2013, 04:21 PM   #1
Grumpy_one
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Aligning pinion angle for perches

I'm in the process of aligning my pinion angle. Simply lining up to point the rear pinion is more of a chore than I thought or I'm trying too hard. I know I want '0' degrees from my rear pinion to my driveshaft angle (double cardan) during operational loads. I'm going to eventually install an anti wrap bar. So I'm going to install it at '0' degrees for now and add shims for 1-2 degrees down until the bar is installed. And yes, I have the the on the weight on axle.

My question: what have you used to do the alignment? I want to get this dead nuts. I've read where people have used a protractor. I can see where you would need one for single u-joint configuration. But simply pointing the pinion at the t-case output seems to be an eyeball judgement. I'd rather be precise. How much room for error do I actually have? I have a laser, might try rigging that up I guess.

I've installed the driveshaft that's going in at the t-case, (needs to be cut down). I then installed the old driveshaft on the rear pinion and try to get them parallel (what a pain). I've thought about having the drive shaft cut down, install it, and then set my angle. Thoughts?

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Unread 11-19-2013, 04:27 PM   #2
82JeepCJ7
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I went out and bought a cheap drywall square and cut the long end down a bit. Put the narrow end of the square on the yolk with it pointing at the output pinon. You may even be able to clamp the thin end in the yolk using the straps to make it hands free.

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Unread 11-19-2013, 07:05 PM   #3
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You are heading in the right direction.

The point you want to align on is not the output itself but just below the centre of the joint. If you are a little bit below then when your suspension compresses under load it will approach and go past the centre of the joint.

How critical this is is related to the angle you are creating at the pinion on the axle. Below is a diagram of the angle changes as they relate to changes in rotation velocity or shafy output speed. A change in rotational velocity atthe pinion will be felt as vibration, a really bad case would cause bunny hops. As you can see it is not a linear relationship and you would have to be a long way out to feel vibration and then it would quickly change to something nasty. At 15 degrees you would feel vibrations, at 30 degrees the axle would be tearing apart with a 30% change in axle speed every half turn of the driveshaft. At 5 degrees it would be hard to detect.

With a standard prop the joints at either end are out of phase by 90 degrees and canecl each other out. Your CV joint has a complete two joint assembly inside it which self cancels, leaving a solitary joint at the pimion which is the joint you see in this graph. From the graph the importance of keeping that single joint from flexing can be seen but it also gives a cluse as to how much misalignment can be tolerated.
ujoint1.png

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Unread 11-19-2013, 07:49 PM   #4
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http://www.tomwoodscustomdriveshafts.com
<a href="http://www.tomwoodscustomdriveshafts.comhttp://files.meetup.com/4119962/Steering-and-suspension-basics.pdf" target="_blank">http://files.meetup.com/4119962/Stee...ion-basics.pdf
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Unread 11-19-2013, 08:35 PM   #5
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I don't see why you couldn't cut the drive shaft and then set your pinion angle with it installed. As long as the pinion angle is fairly close to the final position, the measurements needed for the shaft length will be close enough.

Not sure what the question is about angle measurements. One of the best ways to measure angles is with a cheap angle meter from Home Depot etc. Tons of write ups on measuring/setting up the drive lines, such as ......

http://www.stu-offroad.com/axle/pinion/pinion-1.htm

http://www.4crawler.com/4x4/CheapTri...n-Measurements

Hope this helps.

Good Luck
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Unread 11-19-2013, 08:57 PM   #6
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I know what the angle needs to be, it's a matter of execution. I'm interested in the method in which these angles are achieved. Hard to measure the angle of the shaft with it not attached at both ends. My dilemma is getting the angle of the pinion right before the draftshaft is installed. I think I'll just have the drive shaft shortened install it and go from there. Thanks all
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Unread 11-19-2013, 08:57 PM   #7
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Quote:
Originally Posted by 82JeepCJ7 View Post
I went out and bought a cheap drywall square and cut the long end down a bit. Put the narrow end of the square on the yolk with it pointing at the output pinon. You may even be able to clamp the thin end in the yolk using the straps to make it hands free.

What you have there should work absolutely fine, it is cheap and accurate and takes out any guess work.
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Unread 11-20-2013, 08:22 AM   #8
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You are making it harder than it needs to be.

Get the driveshaft cut to the proper length and eyeball it once it's installed. It doesn't need to be dead nuts zero as it will move, even with an anti-wrap bar.

And please, don't use shims! That just defeats the purpose of cutting and welding perches. As said, it will still move with an anti-wrap bar. You will just limit the movement with one so that the springs don't deflect enough for things to start going bad.
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Unread 11-20-2013, 09:01 AM   #9
Grumpy_one
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Quote:
Originally Posted by CSP View Post
You are making it harder than it needs to be.

Get the driveshaft cut to the proper length and eyeball it once it's installed. It doesn't need to be dead nuts zero as it will move, even with an anti-wrap bar.

And please, don't use shims! That just defeats the purpose of cutting and welding perches. As said, it will still move with an anti-wrap bar. You will just limit the movement with one so that the springs don't deflect enough for things to start going bad.

I was only going to use shims until the anti wrap bar was installed, then remove them.

So I installed the old drive shaft just to get a measurement when I noticed that the t-case is slightly offset to the drivers side, measured my old amc model 20 and noticed it is slightly offset by 1.5" to the drivers side. I haven't read anywhere where this is a problem, just an observation. But while the driveline will have a '0' degree angle from the side, it will still have some offset (looking down)to battle. So it won't be at an absolute '0' degree, which is good I'm guessing for the ujoint, getting exercise and not being in the same orientation at most times.
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Unread 11-20-2013, 09:03 AM   #10
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And what I'm saying is that there's no need for shims, ever.
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Unread 11-20-2013, 09:53 AM   #11
Grumpy_one
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Ok, cool.
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Unread 11-20-2013, 05:36 PM   #12
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The front driveshaft on a Quadratrac equipped CJ has a DC joint, and the front pinion is nowhere near pointed at the output shaft.

My rear shaft with a DC joint looks to be 2-4 degrees lower than pointing straight at the output. No vibrations at all.

They are pretty forgiving if it's not perfect.
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