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Unread 10-18-2007, 10:13 AM   #1
bigrobby
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cv driveline angle with ford 8.8

i have an 8.8, obviously and i'm about to put in an sye and cv driveshaft. conventional wisdom has you set up the pinion angle 2 degrees below pointing straight at the output yoke. this is to keep that rear u joint moving a little to keep those needle bearing lubricated.

anyways, with my pinion offset, which creates i think about a 4 degree sideways angle, should i just have it pointing right at the output yoke? (0 degrees).

and if i do, will my axle wrap cause vibrations? im sua

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MY THEORY OF PERPETUAL SPENDING: if i've built my drivetrain strong enough to where i can't break it anymore, i clearly don't have enough power. Strokin' is in the future.
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Unread 10-18-2007, 12:15 PM   #2
Alfons
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Here are a couple of points to consider:
  • The angles you're describing are too small to create any vibration even with single cardan joints.
  • The 2 degree angle is basically a rule of thumb (I refer to it as "a few" degrees instead of 2) - it doesn't remain static. Time and driving tend to cause everything to settle, reducing that angle.

I have an 8.8 with roughly the same angles vertically and horizontally and have no problems. In my opinion, the emphasis should be on the droop angle to get the right CV joint, shaft balance, and adequate shaft slip.
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Unread 10-18-2007, 12:32 PM   #3
bigrobby
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right now with my single cardan setup i do have a vibration under acceleration, slight under a quick downshift too from the axle wrapping the other way. my angle is correct for single cardan, parallel outputs. the offset angle may be as much as 5 degrees which couple with any axle wrap could cause some bad vibrations. i do have somewhat anti wrap perches ready , about 6 inches of contact to the springs.

i'm doin this conversion to get rid of my vibrations and i'm just worried i'm gonna spend money to make it worse. tom woods which is where i got my driveshaft says there have been quite a few vibration problems with this setup

the cv joint should be right, as well as the shaft balance and and slippage.
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92 yj, 4.0 H.O. with crane cam 753901 and lifters/ ford 8.8 track lock and disc rear/3.73/ 231 HD chain & sprocket/ Teralow HD SYE/Tom Woods DS/ bout 4 inches mixed susp lift/ 33" BFG muds/ crapload more.

MY THEORY OF PERPETUAL SPENDING: if i've built my drivetrain strong enough to where i can't break it anymore, i clearly don't have enough power. Strokin' is in the future.
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Unread 10-18-2007, 01:41 PM   #4
chupacabrah
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the sideways angle is negligable.
as long as your driveshaft is the right length w/ right amount of slip, and your verticle angle is in the ballpark, shouldnt be a big deal.


my pinion points a little ABOVE my tcase, and i dont have any vibes.
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Unread 10-18-2007, 01:44 PM   #5
jeepinMatt
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SUA you shouldnt have much if any axle wrap. and i just pointed mine somewhere close and its fine
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Unread 10-18-2007, 01:50 PM   #6
jeepster93
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Quote:
Originally Posted by chupacabrah
the sideways angle is negligable.
as long as your driveshaft is the right length w/ right amount of slip, and your verticle angle is in the ballpark, shouldnt be a big deal.


my pinion points a little ABOVE my tcase, and i dont have any vibes.
Me too.
There is about a 2 inch offset on the pinion, towards the pass side. Not aware of being able to do anything about that.
When you get your double carden driveshaft, just have them build it with a 4 inch slipjoint, instead of the standard 3.
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Unread 10-18-2007, 07:27 PM   #7
bigstinger
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I'm curious as to why SUA would have less axle wrap than SOA? the way I see it, the size of the tire determines the moment arm around the axle. to your point, with an SUA rig you can only run up to a certain size tire, but as I see it big tires = axle wrap
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Unread 10-18-2007, 08:15 PM   #8
ufatbastehd
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Quote:
Originally Posted by chupacabrah
the sideways angle is negligable.
as long as your driveshaft is the right length w/ right amount of slip, and your verticle angle is in the ballpark, shouldnt be a big deal.


my pinion points a little ABOVE my tcase, and i dont have any vibes.



Same here I'm either right at or a hair above and no vibes


Last edited by ufatbastehd; 10-18-2007 at 08:28 PM..
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Unread 10-19-2007, 07:19 AM   #9
chupacabrah
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Quote:
Originally Posted by bigstinger
I'm curious as to why SUA would have less axle wrap than SOA? the way I see it, the size of the tire determines the moment arm around the axle. to your point, with an SUA rig you can only run up to a certain size tire, but as I see it big tires = axle wrap

it's mainly because of the way the force is applied to the spring. SUA, it just doesnt have much opportunity to wrap. SOA, it's more of a common thing, which is why a traction bar is needed.

maybe someone else can shed a little more light on the dynamics of this
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Unread 10-19-2007, 08:33 AM   #10
mean90yj
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Axle wrap is one of the biggest concerns with a SOA lift. Axle wrap is when the torque on the axle tube tries to rotate the axle pinion up when under power. This twist causes the leaf springs to twist up into an 'S' shape then snap back which leads to loss of traction, wheel hop and usually broken parts. With a SOA lifted vehicle, axle wrap (also called spring wrap) is usually worse because there is more leverage for the twisting axle to work against the springs.....you're welcome
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Unread 10-19-2007, 09:25 AM   #11
bamato
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I run my CV double cardon on my 8.8 at about 2 degrees below center. And it runs perfect. Not saying thats the case for you too, just that it's a good setup. Keep in mind, even if you measure things perfectly before you start, chances are the angle wont be *exactly* the way you predicted. Things settle, other stuff affects pinion angle, like spring tension and the height of your axle mounts themselves.....
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Unread 10-19-2007, 10:17 AM   #12
93YJfalcon
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Mine is pointed right on (or maybe 1 above). I'm planning ahead for a flatskid. It has been that way for a year with no vibe issues, but I'm on my 3rd u-joint. (edit - the rear pinion u-joint that is)
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