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post #46 of 228 Old 12-17-2010, 09:59 PM
quadna71
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Originally Posted by mrblaine View Post
Also, does the harmonic seem like it cycles from front to rear through the vehicle and then start over?
Yes, it does that with mine. I've been sporadically trying to pin down the pulsating vibration in my Jeep for a couple years.

Rotated the tires - no change.
Road force balanced the tires - no change.
Replaced all my seized control arm heim joints with sealed flex joints - no change.
Pulled my front driveshaft off - no change.
Pulled my rear driveshaft off - big change for the better.
Drifted my pinion up and down a few degrees - aside from the expected onset of vibes corresponding to accel/decal - no change.
I checked all my ring bolts when installing a new diff cover last week - all was fine.

I think that either my driveshaft has a bad u-joint that isn't obvious, needs to be rebalanced, or I may have mucked up my output shaft.


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post #47 of 228 Old 12-17-2010, 10:39 PM
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Originally Posted by Unlimited04 View Post
I'll have him check it on Monday. Thanks!
Jack up the rear wheels and wind it up to 65 and see if it has the vibes. Lifting the rear wheels will take the load off the differential gears.

I had a bad driveline angle when I bought my jeep and it literally smashed needle bearings in the rear drive shaft U-joint into powder in less than 100 miles. I couldn't detect any vibrations, I only detected the driveline slapping when the needle bearings were shot. So I can't imagine that the drive shaft is vibrating enough that you can detect it while driving and you don't have U-joints failing all over the place.
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post #48 of 228 Old 12-19-2010, 07:30 PM
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I kind of question the transfer case/output shaft being bent, I have a brand new SYE that had all new bearings and seals. I wonder if its a low fluid thing in the T-case.

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post #49 of 228 Old 12-19-2010, 07:43 PM Thread Starter
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Originally Posted by rlk_99 View Post
I kind of question the transfer case/output shaft being bent, I have a brand new SYE that had all new bearings and seals. I wonder if its a low fluid thing in the T-case.
Fluid is fine (ATF+4), t-case output shaft is not bent in any way, nut is torqued to spec with a Snap-On wrench.
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post #50 of 228 Old 12-19-2010, 08:03 PM
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It almost sounds like a bent carrier in the rear diff. I'd have them check that too while you have your jeep at the shop.

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post #51 of 228 Old 12-19-2010, 08:31 PM
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Originally Posted by LJameson View Post
It almost sounds like a bent carrier in the rear diff. I'd have them check that too while you have your jeep at the shop.
seen this as well during R&P installs. too much runout can cause vibes.

Old stretch thread: http://www.jeepsunlimited.com/forums/showthread.php?t=403448
New stretch thread: http://www.rockymountainextreme.com/showthread.php?t=48591
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post #52 of 228 Old 12-19-2010, 08:39 PM
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The carriers were replaced with brand new true tracks at install. So if the carrier is bent it was done by the manufacturer. If the carrier is bent it would make gawd awful noise from the gears. Not to mention do you think a bent carrier vibe would go away if you took the DS off???? LMFAO you guys are killing me.

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post #53 of 228 Old 12-19-2010, 08:45 PM
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Ever since I re-geared to 4.88s, I have had the same pulsating vibration at about 60 mph. I chased it around for a while and then just gave up. Between the belly up, SYE, aftermarket drive shafts, lockers, steel wheels, chewed up 35"tires, hand full of U-joints, It could be anywhere. That was 30,000 miles ago. PRP suspensions seats soak it up nicely and I only notice it in the rear view mirror now Someday something will let go and I'll figure it out
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post #54 of 228 Old 12-19-2010, 08:52 PM Thread Starter
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Josh, I'll bring a new pinion seal & diff oil. After the drive, I'll pull the cover and I'd like to have you check the backlash, preload & gear pattern, just to eliminate possibilities. I've changed the fluid once, spun the diff and didn't see anything wrong...but I don't really know wtf i'm looking for, lol.
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post #55 of 228 Old 12-19-2010, 08:55 PM
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Hey what do ya know... I'm not alone! Since I have regeared to 4.88s, I have gotten vibes from 70 on up. I just figured it was my ****ty rear driveshaft. Gears, pinion, angles, bushings are all good. I'm hoping with a new driveshaft or rebalance the vibes will go away. If not, oh well I can live with it. The vibes aren't too bad. I never cruise above 70mph anyhow.
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post #56 of 228 Old 12-19-2010, 09:00 PM
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I just went from 4.56s to 4.88s a couple months ago. Before the gear change I had a little bit of vibe. But now it is a lot more noticeable and I can feel it at lower speeds with 4.88s. I know it is the DS cause still do not have a SYE and DCS. I have geared over 60 axles this year. I did one with 5.13s and another with 5.38s. Neither had any vibes. The 5.13 was a Ranger with 35s. It would run 90 mph down the highway with no vibes. The 5.38 was 09 JK Rubi. Guy was cheesing said I did a great job he drove it on a 1500 mile business trip day I finished the regear. He just spent big bucks on real HD CV shaft not a double cardan shaft. I never had a vibe that didn't come from the DS or the tires.

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post #57 of 228 Old 12-19-2010, 09:06 PM
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Quote:
Originally Posted by Unlimited04 View Post
Josh, I'll bring a new pinion seal & diff oil. After the drive, I'll pull the cover and I'd like to have you check the backlash, preload & gear pattern, just to eliminate possibilities. I've changed the fluid once, spun the diff and didn't see anything wrong...but I don't really know wtf i'm looking for, lol.
If there was a problem inside you would have seen it when you spun the ring gear. I have to get a bumper finished for guy tomorrow but if you wanna tear it down I will check it once you have it apart. I have 7 gear jobs I need to finish before Christmas.

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post #58 of 228 Old 12-19-2010, 09:21 PM
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Pull the front drive shaft and go for a ride before you mess with a cover, not to mention yanking the carrier to check the pinion preload.

I can't even begin to tell you the amount of time I've spent messing with caster angles to get rid of driveshaft vibs when all along, the front shafts just needed to be rebalanced. r&p is hardly to blame for vibs just because they crop up from a regear and didn't do it stock, you just never got it going fast enough. even a TT can flush out, out of balance CV shafts.

I want your factory 07-up take-off/thrown out JK front/rear Lower Control Arms! Bent ones are perfect also as long as the bushings and cold cut rings are in good shape/useable


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post #59 of 228 Old 12-19-2010, 09:29 PM
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OK so if I understand right you guys can actually feel the vibe not just hear it? Mine is auditable not anything that I feel. Ive got ARB lockes front and rear in mine. It wasnt there then all of a sudden there it was.

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post #60 of 228 Old 12-19-2010, 09:49 PM Thread Starter
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Quote:
Originally Posted by mudb8 View Post
Pull the front drive shaft and go for a ride before you mess with a cover, not to mention yanking the carrier to check the pinion preload.

I can't even begin to tell you the amount of time I've spent messing with caster angles to get rid of driveshaft vibs when all along, the front shafts just needed to be rebalanced. r&p is hardly to blame for vibs just because they crop up from a regear and didn't do it stock, you just never got it going fast enough. even a TT can flush out, out of balance CV shafts.
I've pulled the front shaft and had it balanced, didn't change anything. If I pull the rear shaft the vibes go away. The rear shaft has been fully rebuilt and balanced. Whats your next suggestion?
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