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Firm opinions for sound and vibration

2K views 34 replies 11 participants last post by  Ace High Benny 
#1 ·
Happy New Year!

I'd appreciate firm opinions and solutions.

2004 Rubicon, all stock shape and lift. Let's assume that everything is new:

-Front end
-Shocks
-Front wheel Bearings
-Ball joints
-Mounts
-Control arms
-U-Joints

SOUND: Whoom...whoom...whooom...
SPEED: 50+ Miles
VIBRATION: 50+ Miles

NOTE: Sound & Vibration present in 2WD but go away in 4WD.

I have an idea but will require more input for the fix.

What is your opinion?

Best,
B
 
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#4 ·
I have had vibrations like you are referring to that appear at certain speeds. I rebalanced my tires when they hit 25,000 miles just because, drove around town and all seemed fine. Got out on the interstate and up to speed and instantly realized they messed up the balance. Took it back to them and the back right was 3ozs off.
 
#5 ·
Vibration of the drive shaft - results of inspection

One more time, with the intentions of helping the JEEP community, here are my findings:

- It appears so that the new U-Joints on the double cardan joint of the front drive shaft have excessive "axial movement". Although all parts are new, this movement should be limited by using thicker retaining clips and be brought back to specs to eliminate vibration.

Here is a good video explaining the process:



I will report on the final outcome after I work on the driveshaft tomorrow.

B
 
#6 ·
Vibration of the drive shaft - results of inspection

UPDATE:

The axial movement of the U-Joints was adjusted to higher tolerances and tires were rotated and balanced.

THIS DID NOT ELIMINATE THE VIBRATION THAT STARTS AT ABOUT 50 M/H.

To make sure that the issue is not a mechanical and caused by the transmission, shifting was controlled and the vibration was still present at 50 M/H - independent of any gear change (BTW, auto).

Next, I am thinking of:

-FAILING DRIVESHAFT
-BAD REAR AXLE BEARINGS

Any other opinions?

BA
 
#9 ·
The thing of most importance (to me) is that is goes away in 4WD.
So when transfer case is engaged, all is well?
Check your transmission mount, the rubber piece that holds the tranny to the cross member. Maybe motor mounts, too.
Any pulsation in rotors (felt through brake pedal) when lightly applying brakes at highway speeds?
 
#10 ·
Thank you for the input.

I am good with "elimination process" :)

-New Transmission mount (MOPAR)
-New Motor Mounts
-No pulsation through the rotors
-To add, the front end is well put together and new - including the steering damper. Nothing is wobbling

The vibration comes from under the vehicle, accompanied by a rotating sound "whooom...whooom...whooom...whooom..."

Cheers,
BA
 
#14 ·
If it truly goes away in 4wd, it could be worn bushings in rear control arms, letting the axle slightly rotate under torque and start vibes? Going into 4hi might slightly reduce the pressure in the rear.


Have you tried removing the rear driveshift & driving in 4hi (essentially fwd) as a test?
 
#17 ·
:) Absolutely not a test!

I consider myself an "expert do-it-yourselfer" (I can rebuild engines & transmissions) and, considering that the vehicle has brand new parts -except for a few, like rear axle bearings - I am really trying to find out the reason for the 50 MH vibration

I will, of course, post the solution.

BA
 
#18 ·
I'd go back to the wheels and tires...

Verify the tires are balanced correctly and all wheels are true and torqued correctly. Also verify that the tires are true. New tires often aren't as round as they should be, and tire shops seem to get the balance 100% right about 50% of the time. lastly make sure you have the correct style lug nuts.

The "no issue in 4WD" is perplexing though. Double check the alignment.
 
#19 ·
Did you have the vibes before changing out all the stuff on your list? Had a similar problem with a Dodge/Cummins . . . it would vibrate on pavement, then when going into a long sweeper corner, it would vibrate then go out of phase, then back in phase . . . a rear brake drum wasn't centered with the wheel studs, and the front tire on the opposite tire was slightly out of balance. Took quite some time to find this.
Jacked up each mounted wheel and checked the run-out with a dial indicator. Found the problem. Good luck, vibes are hard to find sometimes.
 
#20 ·
Did you have the vibes before changing out all the stuff on your list? Had a similar problem with a Dodge/Cummins . . . it would vibrate on pavement, then when going into a long sweeper corner, it would vibrate then go out of phase, then back in phase . . . a rear brake drum wasn't centered with the wheel studs, and the front tire on the opposite tire was slightly out of balance. Took quite some time to find this.
Jacked up each mounted wheel and checked the run-out with a dial indicator. Found the problem. Good luck, vibes are hard to find sometimes.
While your approach may be right, will all things changed / new (including u-joint & centering yoke for the front driveshaft), I am leaning towards other possibilities like, bent driveshaft, rear axle bearings...

BA
 
#25 ·
I had a pulsating vibe that I couldn't get rid of. Finally took it to a specialist and they stated the pinion depth was wrong on the front axle (I had just bought the axle). They changed the depth and put in a new crush washer and ran a pattern, after that I had no more vibe.
 
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#27 ·
Had both drive shafts re balanced at an industrial drive line shop, had new motor/trans mounts installed, wheel alignment(s), as someone mentioned . . . a wheel may be balanced, but that doesn't mean the mounted tire is round. Check yours with a dial indicator. You may be surprised what you find.
 
#28 ·
This is probably not the solution but who knows. It did happen to me once. They balance the drive shafts by welding little tabs of metal on them. I had one of these remove itself and go flying down the road. Yes a very odd vibration at about 50 mph was the result. Good luck and I hope you find it.
 
#30 ·
Decided to go to a "specialist"

It will, perhaps, be for the first time in about 20 years that I'll taking a vehicle to a mechanic.

With all the money I save by doing the major work myself, I am OK with it.

SOMETIMES, THE RELIEF OF A DIAGNOSIS AND A FIX IS PRICELESS!

The Rubicon is going to a "specialist" tomorrow.

I'll report the findings and the outcome of the fix.

BA
 
#31 ·
Diagnosis and recommendation question

I had already suspected it and, it was indeed the case.

With all the parts being new and, after checking the vehicle on the lift, the mechanic was able to attribute the vibration that started at 45 M/H to a failing front driveshaft

We are talking about a stock 2004 Rubicon. When inquiring about driveshafts, the first name that jumps to you is "Adams" .

Has anybody had a BAD experience with Adams? Do you suggest other brands to look at?

For those who live around Tucson, I highly recommend the services of MY MECHANIC; very honest people!

Best,
BA
 
#35 ·
Vibration / final diagnosis & fix applied



With all the part well maintained, the "specialist" had determined that the vibration starting at 45 m/h was caused by a faulty front drive shaft.

Today, I replaced it with an Adams - Rubicon version.

OUTCOME: The vehicle is fixed and the vibration completely gone. The ride is very smooth.

Bottom line, if you are certain that all the parts are new, tires balanced and the mechanical system is functioning properly, then it is the drive shaft that is causing the vibration. In my case, the front one.

ISSUE FIXED!

Best,
B
 
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