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Author Topic: Rear driveshaft vibe  (Read 5612 times)

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Offline Vinman

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Rear driveshaft vibe
« on: February 12, 2012, 06:48:37 PM »
05 LJ Rubicon.
Stock suspension, no lift yet.
33 Engineering belly-up skid
1" MML
Adjustable rear upper control arms.

I get a nasty vibe starting at 60 MPH and continues as speed increases.
I have played with pinion angle from about 2.5 degrees below driveshaft to 1 degree below DS angle, no change at all.

- New CV shaft just built
- Vibes are much worse with CV shaft then with stock shaft and stock CAs.
- Absolutely ZERO vibes at any speed with rear shaft removed.

Am I missing something here? Any ideas? Maybe a bad driveshaft balance?

Any input is appreciated.

Vince
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Quote from: Bnine link=topic=25904.msg162940#msg162940      date=1341881306
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Offline SwampSinger

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Re: Rear driveshaft vibe
« Reply #1 on: February 12, 2012, 07:15:43 PM »
How much does the Belly up brings everything up? ... may be you need more then 1"MML.

With a CV you should be ok though...

When I put a tummy tuck on Bonnie's 06 rubi... I raise every thing pretty much the same....1.25 MML+1.5" TT + 1.25" body lift (which des not affect the drive line at all)...

You have a longer wheelbase and a longer driver shaft also. You should be ok.

How's your pinion angle compare to the driver shaft?  may be it binds there on the yoke.
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Offline Vinman

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Re: Rear driveshaft vibe
« Reply #2 on: February 12, 2012, 07:40:26 PM »
Quote from: SwampSinger on February 12, 2012, 07:15:43 PM
How much does the Belly up brings everything up? ... may be you need more then 1"MML.

With a CV you should be ok though...

When I put a tummy tuck on Bonnie's 06 rubi... I raise every thing pretty much the same....1.25 MML+1.5" TT + 1.25" body lift (which des not affect the drive line at all)...

You have a longer wheelbase and a longer driver shaft also. You should be ok.

How's your pinion angle compare to the driver shaft?  may be it binds there on the yoke.

I didn't measure the actual increase in t-case output height between stock and the bellyup but I would guess it's about 2 inches.
The pinion is pointed almost exactly at the t-case so the pinion is about 1 degree below driveshaft angle (to compensate for pinion movement when power is applied)
According to the numbers and angles, I should have no issues with my current setup, well within specs.

Here are a couple of pics.



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Offline Spinalguy

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Re: Rear driveshaft vibe
« Reply #3 on: February 12, 2012, 08:09:29 PM »
my best guess is your driveshaft is not balanced properly.
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Offline Vinman

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Re: Rear driveshaft vibe
« Reply #4 on: February 12, 2012, 08:20:29 PM »
Quote from: Spinalguy on February 12, 2012, 08:09:29 PM
my best guess is your driveshaft is not balanced properly.

That's what I'm leaning towards as well.

I must be the unluckiest guy in the world when it comes to having driveshafts built or repaired. EVERY time I had one built or repaired the shop got it wrong, this one is no exception. I was very specific when I ordered it that I wanted a greasable center section and NON greasable u-joints. When I went to pick it up, all u-joints were greasable >:( >:( >:( .
I had to make a second trip so they could replace the u-joints. This leads me to the possibility they did not re-assemble it the same way they took it apart resulting in a brand new, unbalanced shaft.

Vince 
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Offline SwampSinger

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Re: Rear driveshaft vibe
« Reply #5 on: February 12, 2012, 08:23:01 PM »
Quote from: Spinalguy on February 12, 2012, 08:09:29 PM
my best guess is your driveshaft is not balanced properly.

True...

It might be also the case of empty Labbatt 50  you have in the back of the Jeep  ;).
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Offline Rubi03 jef

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Re: Rear driveshaft vibe
« Reply #6 on: February 12, 2012, 08:43:18 PM »
go have it re balanced    and  check your pinion bearing if u have any movement in it ..
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04 rubicon <4'' X series RC lift, 1.25'' RC body lift, 1'' RC MML, CV rear drive shaft,  Stubby front bumper, CB,35 MTZ" ,Hi Lifter 54'',LED tail lights , flat fenders, LED front Flasher, half doors, Light force spots, and CDN M101 custom Military trailer

Offline Vinman

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Re: Rear driveshaft vibe
« Reply #7 on: February 12, 2012, 10:20:28 PM »
Quote from: SwampSinger on February 12, 2012, 08:23:01 PM
True...

It might be also the case of empty Labbatt 50  you have in the back of the Jeep  ;).

When I have the top off the Jeep, I hide my wallet under the case of 50, nobody this side of Nova Scotia will even touch the 50
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Offline Vinman

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Re: Rear driveshaft vibe
« Reply #8 on: February 12, 2012, 10:21:27 PM »
Quote from: Rubi03 jef on February 12, 2012, 08:43:18 PM
go have it re balanced    and  check your pinion bearing if u have any movement in it ..

Zero movement in the pinion bearing, I guess I'll take the driveshaft back for rebalance.

Vince
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Offline FiEND

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Re: Rear driveshaft vibe
« Reply #9 on: February 12, 2012, 10:31:49 PM »
looks to me like it is too straight.  this will wear out the needle bearings and there will be no .... backforce when the phase of the driveshaft wants to shift.  if the shaft can phase in and out at will, it will vibrate.  i wouldnt use a cardan for that angle.  when my shaft dies i am going without the cardan cause my angles are too strait to have one.
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Offline Vinman

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Re: Rear driveshaft vibe
« Reply #10 on: February 12, 2012, 10:39:10 PM »
Quote from: FiEND on February 12, 2012, 10:31:49 PM
looks to me like it is too straight.  this will wear out the needle bearings and there will be no .... backforce when the phase of the driveshaft wants to shift.  if the shaft can phase in and out at will, it will vibrate.  i wouldnt use a cardan for that angle.  when my shaft dies i am going without the cardan cause my angles are too strait to have one.

I have never heard of a problem like you're describing and lots of vehicles run the double cardons with a relatively straight driveline. The stock front TJ driveshafts don't have much of an angle and don't have any prroblems.

Everywhere I've read suggests the pinion should be pointed directly at the t-case output then dropped about 1 degree to compensate for the diff rotation when under load.


Vince
« Last Edit: February 12, 2012, 10:45:05 PM by Vinman »
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Offline morerpmfred

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Re: Rear driveshaft vibe
« Reply #11 on: February 12, 2012, 10:54:27 PM »
All it takes is one of the ujoint cup to installed with piled up needle bearings
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Offline FiEND

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Re: Rear driveshaft vibe
« Reply #12 on: February 12, 2012, 10:58:28 PM »
yea, always boggles me.  im pretty sure when under load the pinion side of the low pinion will lift upwards.  im pretty sure one of the nathans had the same problem with straight or 3 degree +/- angles.  i think +/- 5 degrees fixed it.  ive seen where they suggest pointing the pinion at the transfer case with a cardan shaft but only recall reading that about TJ's.
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Offline Bnine

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Re: Rear driveshaft vibe
« Reply #13 on: February 13, 2012, 07:15:00 AM »
Was the stock flange and dampener removed Vince? If so, it's common with rubi's to have the Lin slide out of the speedo tone ring then fall behind it when you re torque. All which causes a runout issue on the rear output and a subtle vibration.
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Offline Vinman

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Re: Rear driveshaft vibe
« Reply #14 on: February 13, 2012, 07:24:25 AM »
Quote from: Bnine on February 13, 2012, 07:15:00 AM
Was the stock flange and dampener removed Vince? If so, it's common with rubi's to have the Lin slide out of the speedo tone ring then fall behind it when you re torque. All which causes a runout issue on the rear output and a subtle vibration.

Stock flange and damper was re-used and the damper was never removed from the t-case.
This is hardly a subtle vibe Bill, above 60 mph,this thing shakes like a dog pooping razor blades.

Vince
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