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post #91 of 228 Old 12-21-2010, 05:18 AM
williambmac
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Quote:
Originally Posted by Stang5lgt View Post
Two other factors to throw in here. Sean ran 35s 37s. Unlimited is running 33s. Which means more RPMs. Other thing that is new besides the 33s. Is the true track. Next if it was the gears or true track wouldn't the vibes still happen with driveshaft removed. Unlimited said they go away. Unlimited I have spare Advanced Adapter SYE yoke you can borrow if you wanna try changing to a different one.
No there wouldnt be vibes with the rear shaft removed, because now there is no load on the "drive" side of the ring and pinion while accelerating.


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post #92 of 228 Old 12-21-2010, 06:59 AM
MeltdWhiskey
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i've had the same issue from day one of my regearing. i did a lot of what has been mentioned in this thread and it's tolerable now. ..but it's not completely gone. ..i eventually gave up.
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post #93 of 228 Old 01-14-2011, 05:47 PM Thread Starter
Unlimited04
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Update: Still vibrating.

With 31s and 3.73s = driveshaft was going 2900 rpms at 70mph.
With 33s and 4.88s = driveshaft is going 3500 rpms at 70mph.

What's changed since the regear: driveshafts are spinning 600 rpm's faster @ 70 mph, and the gears & carriers. Thats it.

Got the original shaft balanced again, didn't change anything one bit. Balancing was done at speeds around 3000 rpms. The original shaft weighs about 10 lbs heavier than the second shaft. The second shaft is a ZJ front shaft cut down, so its small diameter & small splined. The second shaft shows less vibes. Both are balanced by the two best driveshaft/drivetrain shops in the area.

Had Stang5lgt (Josh) check the diff over today. Diffs do not howl - sound same as stock. I took him on a ride so he could feel the vibes, then pulled the rear shaft and drove in front wheel drive to verify no vibes. Backlash was 7-10 thousands on all teeth, so all within spec. Basically zero side to side movement in the ring gear, and zero runout issues with the carrier (so no carrier wobble). Absolutely no unexplained resistance when driving the ring gear by hand with the pinion yoke or a tire...bearings have broken in nicely...everything is very smooth. Pinion is nice and tight.

The wear pattern was nice, but he also checked the pattern with marking compound...all looks good:



So it ain't the gears either.

WTF!!?!?!?!

I'm clueless.
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post #94 of 228 Old 01-14-2011, 05:54 PM
Stang5lgt
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DS speed calculation.


33 inch tires at 65 mph
RPM x OD x RG x DSRPM
1703 x .69 x 3.73 = 4383
2228 x. 69 x 4.88 = 7502
35 inch tires at 65 mph
2101 x. 69 x 4.88 = 7074

RPM calculator. Find your OD gear and use that ratio to figure you RPM.
http://www.csgnetwork.com/multirpmcalc.html

OD - Over Drive gear transmission
RG - Rear Gear ratio
RPM - Engine Revolutions Per Minute
DSRPM - Drive Shaft Revolutions Per Minute

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post #95 of 228 Old 01-14-2011, 05:58 PM
AZJeepNewbie
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Yup. Been there, done that, got the T shirt. I'm convinced that the folks who say they don't have the problem at these ratios simply don't drive their Jeeps that fast. I believe our driveshafts are just not designed to turn at those speeds at these angles.

My current plan is to go with a front locking hub conversion. That ought to do it, as long as it doesn't introduce some new problem. I'm currently watching one fellow to a hub conversion on ROF. Assuming that works out for him, I'm getting mine. The biggest pisser is having to buy all new wheels.

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post #96 of 228 Old 01-14-2011, 06:10 PM Thread Starter
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Quote:
Originally Posted by Stang5lgt View Post
Here is actual DS speed calculation.
33 inch tires at 65 mph
RPM x OD x RG x DSRPM
1703 x .69 x 3.73 = 4383
2228 x. 69 x 4.88 = 7502
35 inch tires at 65 mph
2101 x. 69 x 4.88 = 7074
I don't think your math is correct Josh. The OD just lowers the engine RPM, it doesn't change the driveshaft RPM at any given MPH. Driveshaft speed only depends on tire size and diff ratio...make sense?

I calculated the driveshaft speed by assuming it the same as the engine speed with a top gear ratio of 1:1.

I used www.4lo.com and verified with this site.
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post #97 of 228 Old 01-14-2011, 06:12 PM
Stang5lgt
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Quote:
Originally Posted by Unlimited04 View Post
I don't think your math is correct Josh. The OD just lowers the engine RPM, it doesn't change the driveshaft RPM at any given MPH. Driveshaft speed only depends on tire size and diff ratio...make sense?

I calculated the driveshaft speed by assuming it the same as the engine speed with a top gear ratio of 1:1.

I used www.4lo.com and verified with this site.
Yeah your right I should have left the gear ratio out of the figure and used one as drive gear. 600 - 800 rpm doesn't seem like a lot.

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post #98 of 228 Old 01-14-2011, 06:47 PM
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I actually got mine to quit the pulsating vibrations last week. Swapped in a set of 1" Brown Dog motor mounts and poof, vibes were gone. I have no idea if it corrected my front drive shaft angle a little or if my old motor mounts were just shot but whatever it was my vibes are now gone.

Might be worth a try.

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post #99 of 228 Old 01-14-2011, 06:49 PM Thread Starter
Unlimited04
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Originally Posted by kolky View Post
I actually got mine to quit the pulsating vibrations last week. Swapped in a set of 1" Brown Dog motor mounts and poof, vibes were gone. I have no idea if it corrected my front drive shaft angle a little or if my old motor mounts were just shot but whatever it was my vibes are now gone.

Might be worth a try.
already have a Currie 1" MML, been on for several years now actually.
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post #100 of 228 Old 01-14-2011, 06:52 PM
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Quote:
Originally Posted by AZJeepNewbie View Post
Yup. Been there, done that, got the T shirt. I'm convinced that the folks who say they don't have the problem at these ratios simply don't drive their Jeeps that fast. I believe our driveshafts are just not designed to turn at those speeds at these angles.

My current plan is to go with a front locking hub conversion. That ought to do it, as long as it doesn't introduce some new problem. I'm currently watching one fellow to a hub conversion on ROF. Assuming that works out for him, I'm getting mine. The biggest pisser is having to buy all new wheels.
Before you get real earnest about that or any hub conversion, you should give me a call.

I am Savvy
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post #101 of 228 Old 01-14-2011, 08:03 PM
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My LJ has the same vibes from the rear. I have a brand new SYE, fully rebuilt/shortened/balance ZJ front driveshaft. Driveshaft and rear pinion angles match at 15 degrees. The vibes started with the 4.88 gears. Back then I was running the stock skid and stock rear driveshaft, once I did the tummy tuck the vibes were a loud worse and louder so I quickly did the SYE and new driveshaft. It's better than it was without the SYE, but starting at 68mph or so I have a pulsing vibration.

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post #102 of 228 Old 01-17-2011, 07:50 AM
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Quote:
Originally Posted by mrblaine View Post
Driveshaft and pinion angle. Point the pinion directly at the driveshaft, screw the 1 down BS. Get your driveshaft rebalanced perfectly.

Also, does the harmonic seem like it cycles from front to rear through the vehicle and then start over?
Quote:
Originally Posted by quadna71 View Post
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.
Had the rear driveshaft checked - joints are fine, centering ball is fine, and it's balanced according to the shop. I'm starting to get a little defeated with this resonating vibe. I have to make a long road trip this summer (about 4800 miles) and would love to get it taken care of beforehand. I may steal the driveshaft from my wife's TJ and see how that affects it...at least to eliminate the possibility of the driveshaft still causing it. I'm also swapping out the RE 4.5 springs for a set of Currie progressive 4.0s today. I hate adding more variables into the scenario...but maybe while resetting the pinion I'll stumble upon a cure. Any other ideas?

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post #103 of 228 Old 01-17-2011, 08:51 AM Thread Starter
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post #104 of 228 Old 01-17-2011, 09:02 AM
jermeyg
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I know this might be a lot of work but I wonder if a big change is needed to solve the problem? For example, a transfercase swap with someone willing to let you try theirs for a day or less. Even a rear axle swap. I know if you were close I would let you swap around with my stuff( if I had 4.88 gears, etc) to see if you could isolate the problem even more.

It sucks to see you dealing with this issue for so long!
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post #105 of 228 Old 01-17-2011, 05:22 PM
williambmac
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just out of curiousity what brand ring and pinion, and who set it up?

2000 TJ 5.5 Long arm, lots of extras. R.I.P.
2005 LJ rubi 35's Clayton, lots of extras
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