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Old 11-21-2013, 08:13 AM   #1
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Help with pinion angle

Ok,

A little about my setup. I have a 00 TJ with a OME 2.5 inch lift, a 1.25" body lift, and a 1" MML. I have 8 adjustable Savvy arms, Currie steering, and track bar on 33" tires. I noticed my rear pinion started leaking about 5 or 6 months after installing all of this. I guess I had vibes that I didnít notice or didnít want to notice. Anyway I added a SYE and DC shaft to fix the vibes. The vibe happens around 38 to 45 MPH. above that or below that you donít feel them. I removed the front shaft and still have them. I set my pinion angle in line with the DS. Both were about 12 degrees. This smoothed out the vibe in the coming from the rear of the jeep.

The problem is my pinion will not stay adjusted. If I set it, and then drive it that day, I will notice the vibes starting back. I do about a 24 mile round trip to work and back. When I get home I recheck my pinion and it will be high. I donít understand how the pinion angle could change like that. My trans mount is new. I replaced that when I had the skid off doing the SYE. So anyone have a clue as to why the pinion would change? All the bolts in the control arms, trans mount, Yoke on tcase and axle are tight, along with the bolts that hold the DS. I donít see how this can change. Could weak rear springs cause this? Your help would be greatly appreciated.

Thanks,

Mel

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Old 11-21-2013, 09:51 AM   #2
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checked torque spec on the joints thru bolts? how about the jam nuts, how are you tightening those?

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Old 11-21-2013, 10:12 AM   #3
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Torque on bolts are good. Jam nuts tight. I am using a large wrench and getting the hubby to put the final grunt.
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Old 11-21-2013, 10:32 AM   #4
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What if the rear springs were weak? Yeah I think its a long shot. I know the back sits lower with a full tank of gas. I would not think that would be enough to change the pinion angle that much. I have tried setting it very low, around 3 or 4 degrees low and working up. To me with the MML my tcase looks very tilted. Let we post a pic.
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Old 11-21-2013, 11:01 AM   #5
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Quote:
Originally Posted by Melissas6570 View Post
What if the rear springs were weak? Yeah I think its a long shot. I know the back sits lower with a full tank of gas. I would not think that would be enough to change the pinion angle that much. I have tried setting it very low, around 3 or 4 degrees low and working up. To me with the MML my tcase looks very tilted. Let we post a pic.
These were taken after I set the angle the night before, and drove to and from work the next day. It looks high to me, and I have vibs at 37ish to 45ish. It looks high to me now. I did not have a chance to put the guage on it.
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Old 11-21-2013, 11:05 AM   #6
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Just thinking out loud here, but would a t-case drop kit possibly help with your issue here of the vibes?? I didn't notice if you stated you already had one installed or not.
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Old 11-21-2013, 11:08 AM   #7
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In my experience, I've found that drive line vibes usually get worse with speed, or at least don't go away with an increase in speed. To me, your drive line angles don't look bad. I think I would look elsewhere for the vibes you are feeling. Maybe have wheel balance checked.

If everything is tight, your pinion angle should not really change much. Even weak springs would stay weak and leave ride height about the same unless you were checking it with varying weight in it.
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Old 11-21-2013, 11:09 AM   #8
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With a sye, DC drive shaft, and 8 adjustable control arms I would hope that I would not need a TC drop. LOL If I do I want my money back for all the stuff I added. LOL
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Old 11-21-2013, 11:15 AM   #9
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With a sye, DC drive shaft, and 8 adjustable control arms I would hope that I would not need a TC drop. LOL If I do I want my money back for all the stuff I added. LOL
Very true!!...hahaha
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Old 11-21-2013, 11:18 AM   #10
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It looks (to me) like your pinion angle might be too high.
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Old 11-21-2013, 11:25 AM   #11
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1) could be a tad high, but it's not far off. check with a digital gauge like this. Use some washers to set it on the u-joint cap that's attached to the pinion yoke, and use the driveshaft tube as the other reference. The difference should be between 1 degree down and 0 (both the same).

2) recheck control arm torques are to spec, and jam nuts are tight as all hell.

3) loosely chock the wheels, and pop the t-case in neutral and unhook the e-brake. push up and down on the CV side. if there is any loose feeling/movement, the trans mount is likely bad. I know you said it's new, but the bolts might be loose or something too. The mount side that attaches to the tranny is very picky about proper torque as it's taped into aluminum. you should also be able to rotate the driveshaft slightly to feel the backlash in the gear setup. if there's a lot of slop, somethings wrong in the rear end.

4) check rear tire balance. not likely to be the issue...its a long shot.
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Old 11-21-2013, 11:26 AM   #12
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I know thats the problem. I had it set the night before, drove to work and back to the house, and that is what it looks like now. I dont know of any way that the rear axle could rotate like that.
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Old 11-21-2013, 11:29 AM   #13
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Unlimited, I will check on that tonight. I dont know what could or would cause this. I dont know how something could change that setting that much and still be able to drive the jeep
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Old 11-21-2013, 11:33 AM   #14
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Set your pinion 3 degrees lower than the driveshaft slope. Your pinion angle is way to high in those photos. YOU do not need a t case drop. With only a 2 inch lift you could be getting away with a properly angled single joint shaft. BUT, i would use that nice CV shaft you have. I would not set the pinion even with the shaft slope at ride height. 3 degrees lower at ride height. The pinion climbs upward as soon as you accelerate.
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Old 11-21-2013, 11:40 AM   #15
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Has the actual pinion angle change? As in, have you measured it after your drive? I ask, because my angles have shifted in the past and it ended up being that the transmission mount moved on the skid moving the entire drivetrain and changing my angles.
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Old 11-21-2013, 11:44 AM   #16
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Has the actual pinion angle change? As in, have you measured it after your drive? I ask, because my angles have shifted in the past and it ended up being that the transmission mount moved on the skid moving the entire drivetrain and changing my angles.
Good point here with the trans mount. I only said set it 3 degrees low because it seems shes setting it even with the driveshaft slope then driving it and it has climbed. So i was thinking set it a few degrees low drive it and see what happens. Check the trans mount tho. Those OME springs are soft also, so i wonder if the jeep moves around before it settles the angle.
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Old 11-21-2013, 11:45 AM   #17
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Set your pinion 3 degrees lower than the driveshaft slope. .... The pinion climbs upward as soon as you accelerate.
not on a 4/5-link with JJ's on all ends it doesn't.
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Old 11-21-2013, 11:45 AM   #18
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For those double adjustable types of control arms, you are going to want to hit them with a long breakerbar to get them tight. The torque spec for them is "really freaking tight". I use my floorjack handle over a 1/2" drive ratchet using crows-foot wrenches.


Using these I'm able to work in the tighter spaces under the rig without putting it on a lift.
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Old 11-21-2013, 12:24 PM   #19
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not on a 4/5-link with JJ's on all ends it doesn't.
My bad then, if doesnt change angle with suspension cycling then this should be a simple process to set the angle correctly. Especially with a 2 inch lift.
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Old 11-21-2013, 01:52 PM   #20
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My bad then, if doesnt change angle with suspension cycling then this should be a simple process to set the angle correctly. Especially with a 2 inch lift.
Yes I agree. That is my point. It should not change, and it should be easy to set. I did not check the trans mount yesterday, but they were tight when the skid was installed after the SYE.

Like I said before, I do not see how it is possiable for it to move up, after it being set.
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Old 11-21-2013, 02:33 PM   #21
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Something is definitely moving for the angle to change. The point I was trying to make was that at a glance it seems that your pinion is higher. However, is it your pinion angle that changed or is it your transfer case position that changed? Both would have the same effect on the difference between the angles.

Assuming we start with a perfectly aligned pinion/driveshaft relationship (0 degrees), then rotating your axle up two degrees will give you a s degree difference pinion to shaft (roughly). However, if you leave the pinion the same and you move your transfer case (along with engine and everything else most likely) a bit forward, you could reach the same 2 degree difference without ever changing the pinion angle.
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Old 11-21-2013, 02:41 PM   #22
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Something is definitely moving for the angle to change. The point I was trying to make was that at a glance it seems that your pinion is higher. However, is it your pinion angle that changed or is it your transfer case position that changed? Both would have the same effect on the difference between the angles.

Assuming we start with a perfectly aligned pinion/driveshaft relationship (0 degrees), then rotating your axle up two degrees will give you a s degree difference pinion to shaft (roughly). However, if you leave the pinion the same and you move your transfer case (along with engine and everything else most likely) a bit forward, you could reach the same 2 degree difference without ever changing the pinion angle.
Yes I agree. But I would think that you would hear some major banging around going on if the motor or trans were moving. I will check them tonight when I get home just to make sure.
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Old 11-21-2013, 03:52 PM   #23
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Ok, so since nobody has mentioned this, I figure I would throw it out there.

Is it possible the axle end uca mounts had come cam bolts at some point? Remove the uca nut, and you will notice the slotted holes. Check to make sure the knockouts are still in place. I've seen it happen before. If that's not the problem, set the angle, jump on the bumper s few times, then re-check. Also take your angle finder with you, then check every time you get out.

Also you can put the axle on jack stands, remove the wheels, and reinstall the lugs to keep your drum from flyih off. "Drive" it on the stands. If there are no vibes, remove the front shaft and go for a drive(with tires/wheels installed of course)
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Old 11-22-2013, 10:11 AM   #24
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Ok, so since nobody has mentioned this, I figure I would throw it out there.

Is it possible the axle end uca mounts had come cam bolts at some point? Remove the uca nut, and you will notice the slotted holes. Check to make sure the knockouts are still in place. I've seen it happen before. If that's not the problem, set the angle, jump on the bumper s few times, then re-check. Also take your angle finder with you, then check every time you get out.

Also you can put the axle on jack stands, remove the wheels, and reinstall the lugs to keep your drum from flyih off. "Drive" it on the stands. If there are no vibes, remove the front shaft and go for a drive(with tires/wheels installed of course)
The jeep has never had cam bolts. I am going to spend time this weekend playing with the setup again. I will keep everyone posted about the results. I do plan on removing the rear wheels and taking a look at the shaft and all. The front shaft is removed. So it can only come from the rear of the jeep.

Thanks for all of the help, I will let you know what I find.
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Old 11-24-2013, 11:20 PM   #25
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Hey Melissa

So is the rear axle pinion angle moving??

If you use your angle finder on the rear diff , is it that angle thats changing??

Weight of the vehicle will alter the driveshaft angle some as the body, frame and therfore the TC move up or down relative. The axle does not move except as noted below...

So, if the actual angle of the rear axle is changing, something is loose in the rear control arms, bushings, jam bolts, mounts etc or ...

It could be that the rear arm geometry is not optimum? But if it's not good geometry, the pinion angle will not change even from that if the jeeps ride height is the same before and after you drive the jeep after setting/checking pinion angle.

Ideally, with a Rear CV joint shaft as you have, the pinion angle should stay on the same angle as the driveshaft throughout the range of suspension travel. You said you originally set it this way.

If you set the pinion down a degree from what the shaft angle is, it would be a little better, as was previously mentioned, the pinion torques up during forward acceleration.

Either way, if the ride height of the jeep does not change but the pinion angle does, rear control arm or mounts are moving... holes elongated?? or?

Now if the actual pinion angle is not changing, but the driveshaft angle is (assuming the ride height of the jeep is the same) then your TC/trans/engine is moving around, probably at the rear mount, doubltful that this is happening...

Double, triple check the rear arms (both ends, upper and lower) and the mounting holes at both ends for elongation or damage etc

If it is a rear geometry issue, then setting the pinion angle, then driving, accelerating, braking, adding weight (people, fuel etc) will change the pinion angle as the jeep changes etc. This might cause a vibration, but it should change as the load, weight etc changes?

If you measure the jeeps ride height on flat level ground, check the pinion angle, drive it without anyone else in it, dont add fuel etc, then recheck the ride height, recheck the pinion angle, it cant change unless the rear control arms, mounts, bushings, bolts have moved...

let us all know what you find?

mikey
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Old 11-25-2013, 06:24 AM   #26
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Check the upper control mounting brackets as well. Sometimes they separate from the frame

Upper Control Arm Bracket
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Old 11-25-2013, 06:50 AM   #27
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If your pinion angle is changing, the upper arms are probably adjusting out somehow. Take a marker and run a line down a face of every jam nut and onto the arm after setting it right. Drive around until it looks like the pinion has moved, then check your lines. If one of the jam nut lines isn't lined up with a control arm line, that one is slowly backing off.

Also, i just did the rear adjustable Savvy arms this summer. Mine came with bolts too large for the rear upper axle mounts. I had to wallow out the square holes in the upper axle mounts to larger round holes to take the bolts. If you or your installer did that and opened the holes up too much, the bolt may be moving around in there.

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