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SYE and now 8* shims?

Bmxpunk1369

NAXJA Forum User
Location
Bridgewater, NJ
Right now i am running 4 inches of lift in the back with a 231 and an 8.25 rear. I worked my way up from 2.5* shims all the way to 6* i have now. I still get some vibes over 60 and im thinking my pinion is still too low. Should i go up to an eight degree shim or is something wrong with this setup. Here is a picture of the setup and pinion angle i have now. The DS is balanced and its got all new u joints so i tihnk the problem would lie within the angles.

DSC00225.JPG


DSC00223.JPG
 
judging from your pics, you're high, if anything.

buy an angle finder. it's all guesswork without one.
 
No, that looks way straight.
I'd look at tire balance, tire condition before I added more shims. I run 3.5Deg with a 231 SYE and about 9 inches of lift on 35's. rolls smooth down the road at 60. Of course I can't steer too well, so I usually only run about 50.
Also is that a front D/S? How do you know the D/S is in balance?
 
DaffyXJ said:
No, that looks way straight...QUOTE]

"way straight" doesn't account for axle wind up.

buy an angle finder, your guessing without one.
 
DaffyXJ said:
No, that looks way straight.
Also is that a front D/S? How do you know the D/S is in balance?

Photo's can not be used to judge how strait it is!! You need a angle finder to judge what each of the angles are.

That is a rear DS, it is pretty easy to tell from the photo!!

Michael
 
You can get a magnetic protractor at your local welding supply store. Mine was like 15 bucks.
Just not sure how a measurement sitting still will account for 'axle wind up'? (Think MaXJ might have meant Axle Wrap) which only occurs at acceleration or decceleration.
Axle Wind Up is the term applied to the stress induced when turning in 4WD (Part time) Some Basics: http://www.offroaders.com/info/tech-corner/reading/4wd.htm
However with a double cardan drive shaft, you will want the pinion end u-joint angles of the drive shaft to be with in a degree of each other.
 
i dont know for a fact its balanced but it was on the front of the jeep and it never gave me any problems when i had no lift and i ran 4wd. Maybe it could be out of balance. I do have some nice header downpipe marks on the slip joint part that are visible in the pics that could be it.
 
DaffyXJ said:
You can get a magnetic protractor at your local welding supply store. Mine was like 15 bucks.
Just not sure how a measurement sitting still will account for 'axle wind up'? (Think MaXJ might have meant Axle Wrap) which only occurs at acceleration or decceleration.
Axle Wind Up is the term applied to the stress induced when turning in 4WD (Part time) Some Basics: http://www.offroaders.com/info/tech-corner/reading/4wd.htm
However with a double cardan drive shaft, you will want the pinion end u-joint angles of the drive shaft to be with in a degree of each other.

I meant "axle wind up" per the SAE, as in the motion of an axle about the horizontal transverse axis through its center of gravity.

IMO, offroaders.com could more correctly use the term "drive train wind up" to label what they are describing as it impacts the axles, drive shafts and transfercase.

None the less, I think we are both using valid terms to descibe the same thing. Axle wrap/wind up occurs any time power or braking forces are applied to the axle, not just during acceleration or deceleration, but at steady state cruising as well. At 60 or 70 MPH, a fair amount of power is required to push our beloved bricks through the air. This power is reacted through the springs lin a leaf spring suspension.
 
2xtreme said:
That is a rear DS, it is pretty easy to tell from the photo!!

Michael


Bmxpunk1369 said:
i dont know for a fact its balanced but it was on the front of the jeep and it never gave me any problems when i had no lift and i ran 4wd. Maybe it could be out of balance. I do have some nice header downpipe marks on the slip joint part that are visible in the pics that could be it.



I dunno who to believe...

The owner of the jeep or someone looking at a picture of it...

:rolleyes:
 
this is the rear of my XJ, but it is a front shaft that i pulled from the front drivetrain going from my 231 to LP30. I am going to try a new shaft this week and see if the vibes go away. I was just thinking about the angles when i posted this post. Does that rear pinion look to be parallel to the DS or is it too hard to tell. I tihnk its a little under but my thoughts are the DS isnt balanced and thats giving me problems. I only get vibes at high speed and not with high throttle acceleration. The tires are balanced and there is no front shaft so i know its in the rear driveline somewhere. Any ideas.
 
Bmxpunk1369 said:
this is the rear of my XJ, but it is a front shaft that i pulled from the front drivetrain going from my 231 to LP30. I am going to try a new shaft this week and see if the vibes go away. I was just thinking about the angles when i posted this post. Does that rear pinion look to be parallel to the DS or is it too hard to tell. I tihnk its a little under but my thoughts are the DS isnt balanced and thats giving me problems. I only get vibes at high speed and not with high throttle acceleration. The tires are balanced and there is no front shaft so i know its in the rear driveline somewhere. Any ideas.

Who cares where the DS came from? Or what application it was from. It is now in the rear of his XJ and we still need to know the angles to decide what shim you should or should not be useing!!

Michael
 
ds1.jpg


Take a look at that angle and compare it to your second picture. In my opinion yours looks alittle high. Needs to be a degree or two lower than parallel to the shaft.
 
2xtreme said:
Who cares where the DS came from? Or what application it was from.
Michael

You apparently when you attempted to "school" DaffyXJ...

2xtreme said:
DaffyXJ said:
Also is that a front D/S? How do you know the D/S is in balance?

That is a rear DS, it is pretty easy to tell from the photo!!

Michael

posting SPOBI and not being able to say:

"Dang! Guess I was wrong"

Nice....
sign10.gif
 
Bmxpunk1369 said:
Right now i am running 4 inches of lift in the back with a 231 and an 8.25 rear. I worked my way up from 2.5* shims all the way to 6* i have now. I still get some vibes over 60 and im thinking my pinion is still too low. Should i go up to an eight degree shim or is something wrong with this setup. Here is a picture of the setup and pinion angle i have now. The DS is balanced and its got all new u joints so i tihnk the problem would lie within the angles.

DSC00225.JPG


DSC00223.JPG

First of all what kind of setup are you running? Are you using a CV/double cardan joint off of the t-case? Or are you running plain u joints? If you have a CV the pinion centerline should be lined up with the driveshaft (ideally under light load) If you are running plain u joints, the centerlines of the t-case output shaft/yoke and pinion gear/yoke must be parallel with each other in order to cancel each other out. If they are not parallel they will vibrate because the ujoints are not cancelling their acceleration/deceleration out. Can you figure if your vibes get worse under engine braking/downshifting or with acceleration? Make sure the slip joint is tight too! Here's some driveline 101 for ya. Good Luck:)

FUNKYTEE5

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml
http://www.4xshaft.com/driveline101.html
 
I have studied your picture more closely and I believe I have figured out your problem. First your garage floor is entirely too clean. Please spill some sort of greasy nasty fluid on it. The second is your jackstands, they're neatly placed off to the side where they won't be accidentally run over and they also have entirely too little grease and oil on them as well. I hope this has been educational for you and you'll find that your jeep problems will nearly disappear.
 
As mentioned, all that is necessary is for the output shaft and the pinion to be parallel, driveshaft angles don't matter. If it is only on accel, what you have is axle wrap. You may need stronger rear leaf springs. It will be tough to stop the vibes. I am also assuming you have dropped your t case 1"?
 
Jackhill442 said:
As mentioned, all that is necessary is for the output shaft and the pinion to be parallel, driveshaft angles don't matter. If it is only on accel, what you have is axle wrap. You may need stronger rear leaf springs. It will be tough to stop the vibes. I am also assuming you have dropped your t case 1"?


He said that it happens on accel. The axle wraps at that point, that's why you have the pinion a degree or two lower than pointing directly to the output shaft to compensate for that. You don't want the pinion pointed exactly at the output shaft. Unless I've been misinformed all this time.
 
I am running my xj with 4 in lift and sye, and i had to put in 8* shims to get the vibes to stop becouse with 6* i was still rattlen my teeth. These folks are right, its hard to tell by the pictures. just my 2 pennies but go with 8*
 
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