New Vibration Driving Me Nuts

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LukesfirstJeep

TJ Addict
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Aug 2, 2018
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Location
Central PA
I have a new vibration from my front axle/driveshaft that driving me nuts. I installed a 3" lift kit in my LJ about 5 years ago. Everything was great until I regeared the axles. I resolved the problem with a SYE, Adams double cardan rear driveshaft, and some adjustable upper rear control arms. Pinion and driveshaft angles were within a degree of each other for both the front and rear axles.

For the past several years, I was vibration free. This past Spring, I picked up a vibration that was very noticeable around 60 MPH. I was pretty certain the vibration was from the front, but I ignored it until my front pinion seal started to leak. Eventually, I removed the front driveshaft and replaced the pinion seal. I noticed the the factory balance weight on the front drive shaft had fallen off (looks like the welds rusted through). Without the front driveshaft, there was no vibration up 80+ MPH.

I rebuilt the joints in the front driveshaft and had a local shop balance my driveshaft. When I installed the driveshaft, the vibration returned and was more intense. It still occurred at the same speed as before. I installed an Adams front driveshaft and there was no difference. I remeasured my pinion/driveshaft angles and they may differ by 2 degrees. If you were looking at the front axle from the driver's side, the front axle would have to rotate counter clockwise to match the pinion angle.

IMG_3152.jpg


Other Things I’ve done to try and resolve the problem;

  • I removed the rear driveshaft and drove around in 4WD with the front driveshaft. The vibration was still there.
  • I removed the front driveshaft, again, and the vibration was gone.
  • I checked both front and rear pinions for play while not connected to a driveshaft. Neither had any up/down or in/out play. Both had left/right rotation, which I assumed was backlash. The rear pinion was maybe 1/8” left/right, while the front pinion was a good ¼” left/right rotation.
  • I didn’t notice any up/down or in/out play in the transfer case yokes.
  • The transfer case yokes spins freely.
  • I removed the front differential cover and did not see anything obviously wrong. I could see shiny very fine metal particles, but no large pieces, in the oil.
The vibration reminds me of a bad wheel bearing, except wheel bearing vibrations occur at all speeds and their frequency increases with speed. I'm thinking if it were a wheel bearing, the vibration would exist with or without the front driveshaft installed.

I’m not sure what to do next, and am looking for some suggestions.
 
LukesfirstJeep said:
I have a new vibration from my front axle/driveshaft that driving me nuts. I installed a 3" lift kit in my LJ about 5 years ago. Everything was great until I regeared the axles. I resolved the problem with a SYE, Adams double cardan rear driveshaft, and some adjustable upper rear control arms. Pinion and driveshaft angles were within a degree of each other for both the front and rear axles.

For the past several years, I was vibration free. This past Spring, I picked up a vibration that was very noticeable around 60 MPH. I was pretty certain the vibration was from the front, but I ignored it until my front pinion seal started to leak. Eventually, I removed the front driveshaft and replaced the pinion seal. I noticed the the factory balance weight on the front drive shaft had fallen off (looks like the welds rusted through). Without the front driveshaft, there was no vibration up 80+ MPH.

I rebuilt the joints in the front driveshaft and had a local shop balance my driveshaft. When I installed the driveshaft, the vibration returned and was more intense. It still occurred at the same speed as before. I installed an Adams front driveshaft and there was no difference. I remeasured my pinion/driveshaft angles and they may differ by 2 degrees. If you were looking at the front axle from the driver's side, the front axle would have to rotate counter clockwise to match the pinion angle.

View attachment 477720

Other Things I’ve done to try and resolve the problem;

  • I removed the rear driveshaft and drove around in 4WD with the front driveshaft. The vibration was still there.
  • I removed the front driveshaft, again, and the vibration was gone.
  • I checked both front and rear pinions for play while not connected to a driveshaft. Neither had any up/down or in/out play. Both had left/right rotation, which I assumed was backlash. The rear pinion was maybe 1/8” left/right, while the front pinion was a good ¼” left/right rotation.
  • I didn’t notice any up/down or in/out play in the transfer case yokes.
  • The transfer case yokes spins freely.
  • I removed the front differential cover and did not see anything obviously wrong. I could see shiny very fine metal particles, but no large pieces, in the oil.
The vibration reminds me of a bad wheel bearing, except wheel bearing vibrations occur at all speeds and their frequency increases with speed. I'm thinking if it were a wheel bearing, the vibration would exist with or without the front driveshaft installed.

I’m not sure what to do next, and am looking for some suggestions.
Click to expand...

Your front pinion looks low to me. You say the pinion and DS “may” be 2* different. What are they really?

What are the vibes like? Constant or oscillating?

Where do you feel them? Steering wheel or seat?
 
Your front pinion looks low to me. You say the pinion and DS “may” be 2* different. What are they really?

What are the vibes like? Constant or oscillating?

Where do you feel them? Steering wheel or seat?
Click to expand...
Vibes are constant, and I feel them in the seat.

My angles are 84 and 86 degrees.

IMG_3157.jpg


IMG_3160.jpg
 
Get the tires balanced?
Click to expand...
Mac, that's on my list, but I doubt it will make a difference, since the vibration goes away when the driveshaft is removed.

I keep going back to "when the driveshaft is removed". I removed it again last night and double checked the transfer case's front yoke for movement. There was a little rotation, like backlash in the chain and sprockets, but no other movement.

I think I will disconnect both driveshafts at the transfer case so that I can spin both yokes to see if I can feel any worn bearings. Although, I would think if I had a bad transfer case output shaft bearing, I would feel the vibration at all speeds, and the vibration would get more intense as speed increased.
 
Both yokes spins freely and no roughness felt. I also drained the fluid from the transfer case. It was clean.

My next step is to adjust the pinion angle and have the tires rebalanced.

I want to attach two videos showing how much backlash I have in each axle, but I don't know how. How do I attach a video?
 
Problem Solved. I have a bad tire. It balances on a tire machine, but goes crazy when mounted on my Jeep.

It's been awhile since my last update, but my daughter gave birth to my granddaughter in early December, and then I got busy with the Holidays.

Since my last post I had the tires balanced, new ball joints installed (old ones showing wear but still functional), and wheel alignment. I had a 4x4 shop check the front axle components and ring and pinion bearings. I sent my new front driveshaft back to Adams to double check balance. Nothing was found. Out of desperation, I rotated the front tires to the rear axle. Vibration greatly reduced and not felt through the steering wheel, but mirrors still vibrated.

My spare has a plug in it, but still holds air, so I have not included my spare in the tire rotations. Swapping my spare for each rear tire identified which tires was causing my problems. Externally, it looks fine, and the amount of balance weights used is not excessive, and actually less than some of my other tires.

My tires only have about 20K miles on them and still have plenty of tread, but their date code caused me to replace them.
 
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