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Vibes after lift - need advice

2K views 23 replies 9 participants last post by  Zigg 
#1 ·
Hello fellas,

For the last 6 months I've been working on this new to me 03 Rubi with Dana 44's front and back. Since I bought in last April I've driven it less the 800 miles, I've been working on it instead. Most of this time has been spent removing rust, and painting with rust protector paint. About a month ago, I started to replace all the front end parts, because it had some DW. And I added a lift. To date this is what I've put on it:

1. All 8 Metalcloak adjustable control arms.
2. Front and rear Metalcloak trackbars.
3. Zone 3" Suspension lift with hyrdo shocks.
4. ZJ tie rod & new TJ drag link, and all new ends.
5. Spicer Ball joints.
6. Spicer axle u-joints.
7. Timken hub bearings.
8. Spicer inner axle seals.
9. Zone steering stabilizer.
9. Tom Woods Double Cardan rear driveshaft.

I adjusted the lower control arms (front and rear) to stock length - 15 3/4" and checked axle squareness to the center bolt on skid. I made only a minor adjustment in the front, both front and rear was within a 1/16". I adjusted the drivers front upper to get the pinion angle the same as driveshaft and adjusted the passenger upper control arm so the bolt slipped in. Did the rear as well. The front pinion angle was 7-7.5 degrees, the driveshaft was 7.5. The rear pinion angle was 15.5 and so is the DS.

So I went to test drive it today, Everything seems rock solid, except when my speeds hit 65, I start to feel a vibration in my seat and the steering wheel. The faster I go beyond 65 and it gets worse.

So I'm stumped as to what can be the cause, since my pinion angles are right on. I started to read some past posts on vibes and Waterdog suggested to someone to isolate the problem from the front or rear. He suggested to remove the front DS. So I did that and NO vibes.

So that tells me, obviously that the problem is in the front. But my questions are:

1. If I did this test drive with the DS disconnected and the axle still turning, this rules out any vibes from the axle - right?
2. Since my pinion angle is correct, then my problem should be the front driveshaft (u-joints or balance) - right?

Thanks fellas for any input, advise or suggestions.
 

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#3 ·
Wow...great build. I think you're on the right track. I had a very similar problem on my 99 and it was the socket yoke assy at the cardan joint. Replaced it and the three ujoints and it fixed the problem. Is that your shop in the pictures or your kitchen...sweet.
 
#9 ·
"Is that your shop in the pictures or your kitchen...sweet" - Yah, it makes working on the Jeep and cooking dinner real convenient. Haha - jk. No, I bought those cabinets from Home Depot more then 20 years ago. They were meant for a garage, but they do resemble some cheesy kitchen cabinets I guess.
 
#5 ·
Seems like it would be the front driveshaft because you've isolated the problem to that. Make sure it is phased properly for starters. Did you drop the transfer case? I would assume that you didn't but if you did that could be a problem because as you decrease the angle for the rear shaft you increase the front one. Since you have the shaft out check the u joints and the centering ball, common wear items on the TJ.
 
#6 ·
I would have guessed tire balance until removing front DS made it go away

Sure sounds like front driveshaft
U joints or could even be slightly bent

On the front you usually have to accept some angle pinion to DS to keep a decent caster angle for nice steering
Typically you go to just before vibes

Unless you have manual conversion then you can have better caster as highway no vibes with hubs unlocked

But since you went for no angle pinion to front DS I would have expected no vibes but squirrelly steering


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#8 ·
Well I wanted to start with the same pinion angle and go from there to see if I could get better caster, but with vibes right at the on-set I never made it that far. What is surprising the tire return to center seemed pretty good.

What I measured for caster (I know it's not accurate without a alignment shop benchmark) was 7 on the drivers side and 8.5 on the passenger side. I was expecting more like 5, but as I said I know it's not accurate, so I dismissed it. I checked on the flat spot next to lower ball joint.
 
#14 ·
If you change out the front DS ujoints, you may also need a socket yoke assy. Spicer 211355X. I rebuilt mine recently and replaced everything with new. Several years ago I had a socket yoke assy go bad and it made so much noise...I actually thought it was the transmission. There is a grease point on it but is only accessible with a needle point attachment.
 
#15 ·
Once you have verified that the drive shafts are balanced you will know when you have the correct pinion angles when you no longer have vibes. It doesn't matter what the angle finder says if it still won't run vibe free at the angles you've set it to. Even then, with certain gear and t-case combos, you may not be able to fully dial it out at all speeds. Especially true with the Rubi t-case.
Well I've read a lot of Vibe posts in the last few days, and I've been thinking. I had no vibes before the lift, so I assumed the DS was ok, and it must be angles. But with the 3" of added lift the DS angles have changed, so maybe the DS is the problem after all. I'm looking into replacing the DS with a Tom Woods DS.

Now back to the angles. So much attention is given to pinion angles and rightly so, but the pinion angle is only the vertical plane. What about the horizontal plane. If this angle is off, and the vertical angle is ok, I would imagine the vibes would still occur.

So what determines the horizontal angles? Axle squareness? well i've adjusted front and back to within 1/16". But that squareness is to the frame not the T-Case output. If this is off even a little bit, with the much longer front DS, it will be exaggerated. So it seems to me the connection to the frame and the T-Case is the MM's and the skid mounts.

I don't even know how to measure this - uggg.

Another thought was the track bar effects this horizontal angle right? And for me, after I adjusted the track bar to the correct length, to achieve side to side balance of the tires sticking out, and sitting on the ground at ride height, I had to have my wife turn the steering wheel so I could get the holes to line up. This bolt is under tension - why?

I would think adding a lift, raises the suspension straight up, so if I just lengthened the trackbar to accommodate the lift, the bolt would slide straight in with no bind, and the side to side adjustment should be good. In fact this is exactly the case I discovered in the rear.

So a lot of theories hear, am I on the right track?
 
#16 ·
No a longer difference between attachment points makes less angle for same offset

A longer driveshaft is therefore more tolerant of very or horz offset

This is why a LJ can tolerate a little more lift without a SYE

The shorter driveshaft in the rear is longer in a LJ so a little more lift tolerant




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#17 ·
I am talking more about a geometric point of view. I know a longer shaft means that you will have less of a steep angle at the Cardan joint than a short shaft.

I'm talking more of a misalignment between the tcase and pinion in a horizontal plane. Imagine the tcase was rotated (horizontally) by 1 degree. The longer the shaft is the more misalignment there will be, perhaps in this example, several degrees. It's like aiming a rifle at something 1 foot away and then 100 yards away, 1 degree of mis-aim will not effect hitting the target at 1 foot, but will make a huge difference at 100 yards.

I hope I'm explaining myself.
 
#19 ·
Measuring the angles is easy, use an inexpensive protractor or even your smart phone. Spicer has a unjointed angle calculator online that's real easy to use. You'll need the pinion angle, the output shaft angle, and the driveshaft slope. I could get into how to figure it out on paper but the calculator is easy enough to use.
 
#22 ·
missingtwo...that's a great write up on the vibration. I did the same but I also noticed that my UCA bushings were shot...adding a clunk to the problem. I replaced both front upper bushings, adjusted the control arms 3 full turns to move the output shaft of the front diff...down. It's about at 7 degrees using rough measurement. I also took the opportunity to replace the ujoints and yoke centering joint. I have warn lockout hubs so could get away from the vibration but the clunk from the bushings was bad.
 
#23 ·
Like WaterDog stated, you are over thinking this. If you stated in your initial post that removing the front DS eliminated the vibes, you have pretty much isolated your issue. I would still recommend getting the front DS U-Joints replaced along with a balance before looking at other areas.
 
#24 ·
Well since I adjusted the pinion angle and DS to be equal, and I still have the vibes, I decided it must be the DS.

I bought a new Tom Woods front DS, installed it and ... ugggg, I still have the vibes. No change at all.

Could it be something in the front axle. I ruled everything out in the front axle since the vibes disappeared when I removed the front DS, but I'm wondering if somehow something there is causing it.
 
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