Slight vibration around 54 mph after small lift

blamc70

blamc70

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Sylacauga, AL
I recently purchased a 2004 Jeep Wrangler Rubicon with 64,000 original miles. Jeep looks great but has definitely spent some time on the trail with previous owners. I have done a ton to it, including:

New rear chromoly axle shafts/bearings/seals (the original shafts had a slight amount of runout; front axle shafts are good)
New front passenger axle shaft U-Joint
New U-Joints on rear DS (had a slight "notchy" feeling on axle end of DS)
All fluids changed, including front/rear diffs and tc
New 32" Cooper Discoverer AT3 tires on stock wheels
New upper and lower ball joints on both sides
New front driver wheel hub/bearing
All new front suspension and steering rods/ball joints
Replaced 2" budget boost lift with 2" springs from BDS, plus a 1/2" spacer up front for leveling purposes
New Rancho shocks
New, longer sway bar end links
New sway bar bushings
Plus a hundred other things I'm probably forgetting. All of these were replaced due to wear, not as troubleshooting measures. My problem is, I'm having a very slight, tight vibration in the seat starting around 54 mps, up until around 60 or so, then it seems to fade somewhat. The vibration is there whether I am under load, or clutch is pressed in, or just coasting in neutral, while in that general speed range. For troubleshooting, I completely swapped the wheels and tires with a 2000 TJ that I have with the same tires (1" smaller, but otherwise same). The 2000 has no vibration issues, so I know the wheels and tires are good. The problem remained, even with these known good wheels and tires, so I put my others back on, and rotated them just for fun. The vibration is still present. Next, I removed the rear DS, and drove in 4 High... vibes went away, so it appears to be an issue at the rear of the Jeep. I checked runout on the output flange of the tc... it is running true. I checked for play at the pinion... it seems to be good and tight. I cleaned all of the yoke and flange mating surfaces to make sure there were no burs, dirt, etc... all good. I put the read DS back in, and the problem is still there. Driveline angles all seem to be ok, considering I only did a 2" lift. I did lower the tc with 1" worth of washers, but it didn't help. Pinion angle is 9, ds is 9, and tc is 8. Control arm bushings seem to be ok as far as I can tell. I'm kind of starting to run out of ideas... any thoughts? At this point I'm thinking all that is left that it could be is bad bearings in the TC at the rear output shaft, bad pinion bearing, bad carrier bearings, or DS out of balance.

Any thoughts would be very much appreciated. I have researched this for weeks and read more posts and articles on vibration than I can count. Thanks!
 
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First, a big welcome to WTF!!

Are aftermarket adjustable length control arms installed? I'm wondering how the rear axle's pinion angle could be the same as the driveshaft, which it should not be, unless the rear pinion angle was somehow changed.

How did you measure the rear axle's pinion angle? These photos show a good way to measure the rear pinion angle. The angle finder is placed onto either of the two circled points which are exactly 90 degrees different from the pinion angle. Rotating the angle finder 90 degrees allows it to directly measure the pinion angle. The bottom drawing shows how the rear pinion angle should be the same as the transfer case output shaft angle, parallel to it. The driveshaft angle is whatever it is, it's only important the pinion and t-case output shaft angles are parallel/the same.

That you're feeling the vibrations up through your seat does indicate a drivetrain vibration which is typically pinion angle related. Surprised you still have it with the 1" t-case drop which makes me suspect the pinion angle might be off somehow which it shouldn't be with the factory non-adjustable control arms.

Also when the new u-joints were installed into the driveshaft could they have been seated too deeply which can make them bind a tad?

PinionAngleMeasuring1.jpg

Pinion angle, where to measure from.JPG

2joint_angle.jpg
 
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Thank your for the welcome and reply Jerry. I'm a long time reader of the forum, first time posting.

The control arms are OEM. I assumed the pinion angle ended up in line with the ds because of the 2" lift, which I believe (?) would have rotated the pinion up a tad. However, I've read thread after thread where guys have installed 2" lifts with stock arms, with no issues, so I'm at a loss to explain it. I measured the pinion angle 2 different ways... One as you indicated in the diagram (flat spots on the back of the diff) and also across the yoke ears while the ds was removed. The angle finder I used is a Klein digital angle finder.

In this case do you think I would benefit from rear adjustable CA's so that I could lower the pinion angle a degree or so?

As far as the u-joints, I smacked the yokes a few times to loosen them up a bit before reinstalling the ds. Its possible that they could still be a little tight, but it's the exact same vibration that I was feeling before I changed the u-joints, and they were nice and loose (in a good way) before the change. The only reason I changed them was because the joint on the axle end had a little scarring on one end, causing a touch of a "notchy" feeling.

Thanks!
 
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LONGJP2 said:
The Rubicon driveshaft makes it less likely that your small lift is the problem.
You mentioned the Jeep has been off-roaded, I would get the driveshaft balanced.
Click to expand...

Thank you LONGJP2. I've never had a ds balanced before, but will see if I can find somewhere around the area that does that, and also how much that costs. If its expensive, I may consider putting that money towards a dcds. Of course, that would mean adjustable ca's too. It never ends, does it? :)
 
blamc70 said:
Thank you LONGJP2. I've never had a ds balanced before, but will see if I can find somewhere around the area that does that, and also how much that costs. If its expensive, I may consider putting that money towards a dcds. Of course, that would mean adjustable ca's too. It never ends, does it? :)
Click to expand...

Where are you at in Alabama? There are quite a few of us here. We will try our best to help you any way possible!!

Welcome from the far NE corner of the state!!!
 
blamc70 said:
Thanks John! I'm just outside of Sylacauga, about an hour SE of B'ham.
Click to expand...

Yep know where you are! Check around and ask some of the local 4x4 shops who they use and recommend.

If you up this way, I would recommend Chattanooga Drivelines.
 
Good idea! There are a couple around this area... I'll call them tomorrow and see what they say.

Do you ever come down this way to ride? You mentioned you know where Sylacauga is... wondering if you've hit Skyway or some of the other trails around this area.

Thanks for the suggestion! I will update this thread as I make progress on the problem.
 
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blamc70 said:
Good idea! There are a couple around this area... I'll call them tomorrow and see what they say.

Do you ever come down this way to ride? You mentioned you know where Sylacauga is... wondering if you've hit Skyway or some of the other trails around this area.

Thanks for the suggestion! I will update this thread as I make progress on the problem.
Click to expand...

No sir, but @AndyG may know something about it.
 
Jerry Bransford said:
First, a big welcome to WTF!!

Are aftermarket adjustable length control arms installed? I'm wondering how the rear axle's pinion angle could be the same as the driveshaft, which it should not be, unless the rear pinion angle was somehow changed.

How did you measure the rear axle's pinion angle? These photos show a good way to measure the rear pinion angle. The angle finder is placed onto either of the two circled points which are exactly 90 degrees different from the pinion angle. Rotating the angle finder 90 degrees allows it to directly measure the pinion angle. The bottom drawing shows how the rear pinion angle should be the same as the transfer case output shaft angle, parallel to it. The driveshaft angle is whatever it is, it's only important the pinion and t-case output shaft angles are parallel/the same.

That you're feeling the vibrations up through your seat does indicate a drivetrain vibration which is typically pinion angle related. Surprised you still have it with the 1" t-case drop which makes me suspect the pinion angle might be off somehow which it shouldn't be with the factory non-adjustable control arms.

Also when the new u-joints were installed into the driveshaft could they have been seated too deeply which can make them bind a tad?

View attachment 503890

View attachment 503889

View attachment 503888
Click to expand...

Jerry where do you like to get the forward/output angle - on the balancer maybe ?
 
blamc70 said:
I recently purchased a 2004 Jeep Wrangler Rubicon with 64,000 original miles. Jeep looks great but has definitely spent some time on the trail with previous owners. I have done a ton to it, including:

New rear chromoly axle shafts/bearings/seals (the original shafts had a slight amount of runout; front axle shafts are good)
New front passenger axle shaft U-Joint
New U-Joints on rear DS (had a slight "notchy" feeling on axle end of DS)
All fluids changed, including front/rear diffs and tc
New 32" Cooper Discoverer AT3 tires on stock wheels
New upper and lower ball joints on both sides
New front driver wheel hub/bearing
All new front suspension and steering rods/ball joints
Replaced 2" budget boost lift with 2" springs from BDS, plus a 1/2" spacer up front for leveling purposes
New Rancho shocks
New, longer sway bar end links
New sway bar bushings
Plus a hundred other things I'm probably forgetting. All of these were replaced due to wear, not as troubleshooting measures. My problem is, I'm having a very slight, tight vibration in the seat starting around 54 mps, up until around 60 or so, then it seems to fade somewhat. The vibration is there whether I am under load, or clutch is pressed in, or just coasting in neutral, while in that general speed range. For troubleshooting, I completely swapped the wheels and tires with a 2000 TJ that I have with the same tires (1" smaller, but otherwise same). The 2000 has no vibration issues, so I know the wheels and tires are good. The problem remained, even with these known good wheels and tires, so I put my others back on, and rotated them just for fun. The vibration is still present. Next, I removed the rear DS, and drove in 4 High... vibes went away, so it appears to be an issue at the rear of the Jeep. I checked runout on the output flange of the tc... it is running true. I checked for play at the pinion... it seems to be good and tight. I cleaned all of the yoke and flange mating surfaces to make sure there were no burs, dirt, etc... all good. I put the read DS back in, and the problem is still there. Driveline angles all seem to be ok, considering I only did a 2" lift. I did lower the tc with 1" worth of washers, but it didn't help. Pinion angle is 9, ds is 9, and tc is 8. Control arm bushings seem to be ok as far as I can tell. I'm kind of starting to run out of ideas... any thoughts? At this point I'm thinking all that is left that it could be is bad bearings in the TC at the rear output shaft, bad pinion bearing, bad carrier bearings, or DS out of balance.

Any thoughts would be very much appreciated. I have researched this for weeks and read more posts and articles on vibration than I can count. Thanks!
Click to expand...

Dialing in the pinion angle is where it typically is-

I’ve got an almost identical post 2” lift situation with a 2004 Rubicon I’m about to resolve if possible- PM me if able and I’ll endeavor to follow up. I have a spare rear shaft so I have a couple of ways to approach the job.
 
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AndyG said:
Jerry where do you like to get the forward/output angle - on the balancer maybe ?
Click to expand...
Front pinion angle? It can be measured from either of the two circular points in my middle photo above in post #2. But I've never felt the need to measure my front pinion angle. I would only raise the pinion angle to increase the caster angle until it caused vibrations from excessive pinion angle and then back off a half turn or so on the control arms to lower it until the vibrations stopped.
 
Jerry Bransford said:
Front pinion angle? It can be measured from either of the two circular points in my middle photo above in post #2. But I've never felt the need to measure my front pinion angle. I would only raise the pinion angle to increase the caster angle until it caused vibrations from excessive pinion angle and then back off a half turn or so on the control arms to lower it until the vibrations stopped.
Click to expand...

This part-

To see if my angles are close so it cancels out at the pinion-

5E7F6E4E-5189-41F1-B00D-674541E4572A.jpeg
 
I wanted to post an update, just so the thread isn't left hanging.

Originally as part of my troubleshooting I removed the rear ds and did a test drive in 4 high... the vibrations went away, but there was a little noise coming from the front ds whenever I'd start off in first, and even when changing gears at lower speeds. That led me to think the problem was in the rear, but that I probably needed to check the front ds at some point as well. I was going to get my rear ds balanced today, but when I called the shop yesterday evening they told me they had gotten several shafts in that had thrown them behind, so it was going to take like a week or so to do the balance. So, me being a little impatient I called Shawn at Tom Wood's and talked to him. He suggested that based on my previous tests, the problem could still be in the front ds, so, I disconnected that from the axle last night and took it for a test drive. It was absolutely butter-smooth... no vibrations or noises whatsover at any speed. That, combined with the clunking I was hearing when I did the test drive with the rear ds out is leading me back to the problem being in the front.

So, this morning I finished taking the front ds completely out and checked it more closely. I was expecting to find some bad u-joints, but to my dismay, the u-joints all feel good. No slop or notchiness or anything like that. The front pinion feels tight too... no play there. Of course, it could be the balance on the front ds rather than the u-joints.

I did notice a couple of things that I'm wondering about. First was a very small amount of slop at the slip joint in the front ds. If I grab it on both sides of the slip joint and twist back and forth, there is just a very small amount of play. Is that normal or could that be an issue? Also, what about at the tc input shaft? If I grab that and aggressively shake it back and forth and in and out, there is the very slightest amount of play there... is that normal, or should there be absolutely no play at all in it? It feels very smooth if I rotate it around, and there are no signs of leaks on it at all.

Just wanted to update the thread and get your thoughts on what I've found today.

Thanks!
 
Update on the vibration issue... Still not resolved. I found a bad front wheel bearing (not terrible, but a little play) and replaced it. I also got my new TW front DS installed last night and went for a test drive. Maybe just a touch better, but the slight vibration is still there around 55mph. The only thing I can come up with at this point is there is a slight amount of lateral play at the TC output shaft for the front DS. Should there be any play here? Or is a little lateral movement normal? I'm wondering if the output shaft bearing may be bad...
 
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