OME Spring Lift and Pinion Angles

[SAString]

Worn pinion bearings normally make noise all the time... maybe changing pitch with speed. Not vibrate at a specific speed.

I would re-check the rear shaft... ujoint angles, slip spline, how much does the pinion rotate upward under load? I'd even try remove the shaft for a quick spin (4Hi) to see if it goes away.

Wow hold on.!!... "how much does the pinion rotate upward under load"
That tells me something: I put the rear axle on stands and measured the pinion angles between the slip spline and the rear yoke. They are exactly the same angle (under no load). So are we saying the diff raises the rear pinion yoke up under torque?

Wait a minute... then the pinion angle would change when I apply the load, which may be causing the load vibration! How many degrees are we talking about?

After buying a totally new shaft (and it still vibrated), I bought a JBA Y-Link Extension to improve my pinion angle, but I didn't install it because my angles were fine. If you are saying they change under load....then that's a different story. So I may need to point the diff down a few degrees with the washers.

Someone please chime in if you are familiar with these details.

 

[tommudd]

Wow hold on.!!... "how much does the pinion rotate upward under load"
That tells me something: I put the rear axle on stands and measured the pinion angles between the slip spline and the rear yoke. They are exactly the same angle (under no load). So are we saying the diff raises the rear pinion yoke up under torque?

Wait a minute... then the pinion angle would change when I apply the load, which may be causing the load vibration! How many degrees are we talking about?

After buying a totally new shaft (and it still vibrated), I bought a JBA Y-Link Extension to improve my pinion angle, but I didn't install it because my angles were fine. If you are saying they change under load....then that's a different story. So I may need to point the diff down a few degrees with the washers.

Someone please chime in if you are familiar with these details.

Unless you have something very loose not very much at all. You are not that high to begin with
Done a load of lifts and never have I experienced any of what you have . That's from 2.5 on up over 4 inches

 

[u2slow]

Wow hold on.!!... "how much does the pinion rotate upward under load"
That tells me something: I put the rear axle on stands and measured the pinion angles between the slip spline and the rear yoke. They are exactly the same angle (under no load). So are we saying the diff raises the rear pinion yoke up under torque?

Wait a minute... then the pinion angle would change when I apply the load, which may be causing the load vibration! How many degrees are we talking about?

After buying a totally new shaft (and it still vibrated), I bought a JBA Y-Link Extension to improve my pinion angle, but I didn't install it because my angles were fine. If you are saying they change under load....then that's a different story. So I may need to point the diff down a few degrees with the washers.

Someone please chime in if you are familiar with these details.

The pinion shouldn't rotate up very much if everything is sound... but a couple bad rear bushings (or worn balljoint) will change that. You'd feel it more on a hard acceleration, or towing/hauling a load.

The JBA Y-link extension made the pinion angle worse for me. Basically adds the thickness of the material (~3/8"?) to the length of the UCA, rotating the pinion up a tad. Adding washers for adjustment raises it further. The benefit of the extension is to put the UCA back to approx level (after lift)... taking the strain off the upper arm bushings so they last. Raising the pinion would be good for a CV style shaft, but that's not what we have.

Are you getting an actual vibration? Or is it just a sound? Rolling/swirling/growling noises are usually a bearing issue.

 

[SAString]

The pinion shouldn't rotate up very much if everything is sound... but a couple bad rear bushings (or worn balljoint) will change that. You'd feel it more on a hard acceleration, or towing/hauling a load.

The JBA Y-link extension made the pinion angle worse for me. Basically adds the thickness of the material (~3/8"?) to the length of the UCA, rotating the pinion up a tad. Adding washers for adjustment raises it further. The benefit of the extension is to put the UCA back to approx level (after lift)... taking the strain off the upper arm bushings so they last. Raising the pinion would be good for a CV style shaft, but that's not what we have.

Are you getting an actual vibration? Or is it just a sound? Rolling/swirling/growling noises are usually a bearing issue.

This is a harmonic type vibration, not just sound. I can't pinpoint it. Again I'm running without the front CV shaft and the vibes get worse under load around 50. I'm a bit confused about your Y-link results description. Based on my set-up (with the rear 1" higher than the front) the TC points upwards. That would say, if the diff was to be at the same angle, it should point downward, right? Are you saying the Y-link extension will want to point the diff upwards? Is there no washer arrangement that will point my diff yoke downwards. I'm about to install the y-link this weekend, so maybe a little advice could save me some time.
Thanks,
Steve

 

[tommudd]

It does point the rear diff down
if mounted correctly and right amount of washers installed it does do what it is suppose to do
Wish you were closer, 20 minutes time we'd have it installed and you could see if that takes care of the issue or not

 

[SAString]

It does point the rear diff down
if mounted correctly and right amount of washers installed it does do what it is suppose to do
Wish you were closer, 20 minutes time we'd have it installed and you could see if that takes care of the issue or not

Thanks Tom, I appreciate the offer. We're expecting snow here in KC on Sunday, so I'll need to get both the Y-link and my front shaft re-installed today. I'll post my results. fingers crossed!

 

[SAString]

Deleting.

 

[SAString]

I installed the y-link. I want to post pictures, but I need a URL? I used three washers and the upper control arm is happier, but I didn't find any measurable difference in diff angle ( was hoping it would point lower). The test drive indicated the 50mph vibe is still there. Is it possible to lower the transfer case by adding spacers between the body and crossbar? Maybe that would be a way to reduce the operating angle of the shaft?

 

[tommudd]

Installed the y-link. I created a picture of the final installation with surrounding notes, but I guess I don't know how to post picture to this without having a URL??(help). The Upper control arm looks a lot happier, but even with three washers, it didn't seem to change the diff angle at all. The test drive was inconclusive. Still vibes at 50mph. Is a Transfer case lowering possible by adding spacers above the cross-bar?

NO NEED to lower transfer case
and if you installed it correctly it would of made the front of the diff go down
trying to figure out why you are having issues when 1000s of others haven't

 

[SAString]

NO NEED to lower transfer case
and if you installed it correctly it would of made the front of the diff go down
trying to figure out why you are having issues when 1000s of others haven't

Tom:
Picture attached (per 280pixel requirement) See anything out of place?
Thanks,
Steve

 

[profdlp]

Embedded your picture. Hopefully if it's easier to see more people will respond.

One thing I noticed is that you still have the harmonic balance weight on there. Lots of us have taken them off. Maybe test it out without it? I know that would be ironic, but stranger things have happened.

 

[tommudd]

Tom:
Picture attached (per 280pixel requirement) See anything out of place?
Thanks,
Steve

A lot do away with the Jeep balls also the sway bar
I haven't ran any on any of mine for years
Also remove most that I do lifts on

 

[SAString]

Thanks Prof and Tom;

I appreciate the embedding of my picture (do regular members like me get to do that?)

My KJ is now officially castrated based on what seems to be unanimous advice. The sway bar is still there for now. I can't road test it at speed tonight, since the snow is too deep! I'll let you know if I feel any difference tomorrow.

Yes that would be kind of ironic that the very thing designed reduce vibrations, was causing them.

 

[profdlp]

...I appreciate the embedding of my picture (do regular members like me get to do that?)...

When you are creating a post look for the yellowish image icon. Put the URL between the two tags:

[ I M G ] URL goes here [ / I M G ]

I added spaces to mess the code up so it would be visible.

 

[SAString]

Thanks for the pic post advice! I drove without the Jeep balls for the first time today. can't tell much of a difference, if any. Based on my Y-link picture above, do I have the spacers on the right side of the link to point the differential down in front? As I was reading, "more spacers, more angle" but nowhere does it say, what side or more angle up or more angle down. I should have taken Tom's advice and set the angle then see where the spacers go, but I kept it jacked up on the axle to give me room to work. Just added 3 spacers to the front and tightened it up. Didn't see any angle change in the diff, only the upper control arm.

 

[SAString]

Since I still have the driveline vibes at 50mph, I'm thinking of other things to check:

1. Transfer case rear output shaft bent? (check run-out)
2. Differential yoke runout
3. Another trip to the Driveshaft shop and insist they add weights somewhere. When they built it, it had no weights anywhere. The technician just patted himself on the back and said it didn't need any. I'm suspicious of his supposed perfection.
4. I wish I did a SYE instead of a new $600 stock shaft!

 

[u2slow]

Based on my Y-link picture above, do I have the spacers on the right side of the link to point the differential down in front? As I was reading, "more spacers, more angle" but nowhere does it say, what side or more angle up or more angle down.

Zero washers is as low as the pinion goes with the bracket in that orientation. That's how I run it, and the pinion is still high. If its vibrating, I can't tell. The pinion needs to come down to have the 'ideal' equal & opposite angles depicted in your first post.

I debated attaching it to the *front* side of the cast bracket, and then shimming it with 2-3 washers, but haven't had enough time to play with it.

 

[tommudd]

It seems like this all started when you lifted it, correct ?
If so stop throwing parts at it , thinking other things like an SYE will help when it won't.
Start back through everything, something simple is causing your issues
I've lifted KJs with Ironman, OME, JBA coilovers , BDS ( springs and Bilstein shocks ) any where from 2.5 to 4.5 inches , over 55 of them, no issues / no vibes/ ran down the road fine
So somewhere you have an issue that is causing it that you have missed.
If you brought it to me , I would start at square one, and check everything

On my 03 sit at 2.5 inches front and rear ( JBA coilover ) I have the JBA bolt on tri link sit at same spacs as the stock tri link, working well, well for the last 40,000 miles and any where from 0 to 100 MPH on all kinds of roads

 

[SAString]

Vibration Solved!

VIBRATION SOLVED!

After going through and inspecting everything over again, with numerous test drives and configurations, Dial indicator run-outs on the yokes indicated nothing bent. So, I narrowed it down to the drive shaft AGAIN! I took the original shaft into Inland Truck Parts in Olathe, Kansas and had it balanced after my first set of new u-joints. That didn't solve it. I then switched to Spicer sealed u-joints, that didn't fix it. I went back to Inland for the balance again. Ended up buying a WHOLE NEW custom shaft with new spline yoke and a shiny new harmonic disk. THAT made it worse! I didn't see any weights this time, so I was suspicious. Then I read there was a Jeeper guy named Ron Istas at the Missouri Inland Truck facility. I called Ron and made an appointment, telling him I was suspicious of what the Kansas store had done. Ron drove it, felt the harmonic and had me pull the shaft. He and his team put it on the balance machine (Fantastic facility) and spun it up to high RPM. It was well within tolerance, they even tacked on a small weight to make it perfect. I reinstalled it and Ron drove it again. No improvement. So after a lot of thought, Ron said, "it's got to be that big harmonic balance disc causing a frequency to set-up at 50mph. Pull it off this weekend and see if it helps".

Yesterday, I pulled the shaft and precisely knocked off the disc with a BFH, reinstalled the shaft and went for a drive. IT'S GONE! No vibes at 45-55 even under acceleration! All this work and money and that's all I really needed to do. REMOVE SOMETHING, not add a new everything! Again, Ironic that something intended to reduce vibrations was actually causing them.

 

[Aceofspades]

Interesting. Wonder if that would solve a few more issues. Still have my whirring noise on the one and slight vibes on the other.
Didn’t know you guys took those weights off the rear end either. Each time I did the Y link extenders or upper arm - I re installed them.