YJ 8.8 driveline vibration need advice - JeepForum.com
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post #1 of 35 Old 11-24-2013, 12:11 PM Thread Starter
sardog211
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YJ 8.8 driveline vibration need advice

Ok forum I am about to surrender I have a 89 YJ I6 with ax-15 and 231 with SYE, I just did an 8.8 swap I have been chasing a vibration that occurs occurs around 60 mph and up. Here's the full run down. I have a DC an XJ cut down once for the dana 35 and cut down again for the 8.8. Each time I have been told it is balanced, I had a vibration with the dana 35 installed at 68 mph with the 8.8 it's around 60mph. The other day I took rear driveshaft off an drive it with only front on wow no vibration, installed rear DS and vibration came back. I checked TC yoke this morning with and it was tight no play, I then started vehicle put it in gear and ran it yoke looked great. I also checked angles and if I did it right I have 5 degrees at yoke and 15 degrees at axle pinion. I'm simply at a loss and before I go and buy a new rear drive shaft I want to make sure I am not just wasting money trying guess what it could be. I did notice torque arm bushing was a not tight on torque arm but the transmission mount looked to be good.

I need so serious direction, do I take the driveshaft to a third place to have it checked???

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post #2 of 35 Old 11-24-2013, 03:06 PM
ashland82391
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Quote:
Originally Posted by sardog211 View Post
Ok forum I am about to surrender I have a 89 YJ I6 with ax-15 and 231 with SYE, I just did an 8.8 swap I have been chasing a vibration that occurs occurs around 60 mph and up. Here's the full run down. I have a DC an XJ cut down once for the dana 35 and cut down again for the 8.8. Each time I have been told it is balanced, I had a vibration with the dana 35 installed at 68 mph with the 8.8 it's around 60mph. The other day I took rear driveshaft off an drive it with only front on wow no vibration, installed rear DS and vibration came back. I checked TC yoke this morning with and it was tight no play, I then started vehicle put it in gear and ran it yoke looked great. I also checked angles and if I did it right I have 5 degrees at yoke and 15 degrees at axle pinion. I'm simply at a loss and before I go and buy a new rear drive shaft I want to make sure I am not just wasting money trying guess what it could be. I did notice torque arm bushing was a not tight on torque arm but the transmission mount looked to be good.

I need so serious direction, do I take the driveshaft to a third place to have it checked???
Play in the slip joint?


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post #3 of 35 Old 11-24-2013, 03:47 PM Thread Starter
sardog211
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No play at all I grabbed it and it's tight, everything feels good with the slip joint.
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post #4 of 35 Old 11-24-2013, 03:50 PM
ashland82391
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No play at all I grabbed it and it's tight, everything feels good with the slip joint.
Is it in park/gear when you grab it? If so try it in neutral.


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post #5 of 35 Old 11-24-2013, 05:28 PM Thread Starter
sardog211
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Vehicle is manual so what I did is shifted t-case to neutral spins fine I didn't feel any slop in the yoke. Thanks for your help in hoping someone hits on something I have missed.
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post #6 of 35 Old 11-24-2013, 08:04 PM
Joe Dillard
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By chance - was the drive shaft taken apart at the slip & not slid back together in-phase?
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post #7 of 35 Old 11-24-2013, 08:15 PM
TSEJEEPERS
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Measure you pinion angle and driveshaft angle like this.
http://www.stu-offroad.com/axle/pinion/pinion-1.htm
And get back to us.

93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list.
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post #8 of 35 Old 11-24-2013, 11:04 PM Thread Starter
sardog211
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Joe- it is in phase I did check that I have been talking to someone and since the vibration has used to be at 68 mph now it's at 60 after I shortened again for the 8.8 that it could be that my DS Is to short (17 3/4) on a xj front cut down. Thought is that it is possible that it's just hitting the right harmonics since it is short maybe I need thicker walled tubing to remove that harmonic vibration. I leaning toward getting a Curtis Tatton rear driveshaft made.


TSE- did it just like that both came out at 15 degrees on angle indicator.
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post #9 of 35 Old 04-23-2017, 06:27 PM
NW4wheeler
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Has this ever been resolved? I'm having what's sounds like the same issue. I have messed with my pinion angle with no luck. My drive shaft is fresh built by a driveshaft shop. My 8.8 has no excessive backlash. I have the jb conversations super short Sye. I've rotated my tires. The vibration feels as if it's coming from the back relative to vehicle speed once I get to 60mph i can start to feel it and by 70mph it's very noticeable. Please help.
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post #10 of 35 Old 04-23-2017, 11:44 PM
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Originally Posted by NW4wheeler View Post
Has this ever been resolved? I'm having what's sounds like the same issue. I have messed with my pinion angle with no luck. My drive shaft is fresh built by a driveshaft shop. My 8.8 has no excessive backlash. I have the jb conversations super short Sye. I've rotated my tires. The vibration feels as if it's coming from the back relative to vehicle speed once I get to 60mph i can start to feel it and by 70mph it's very noticeable. Please help.
This is a long shot, but is there a chance that the two halves of the driveshaft were separated and then put it back together at some point before you installed it? If that happened and it wasn't marked for orientation it could have been reassembled 180 degrees off which very likely would throw it out of balance.
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post #11 of 35 Old 04-24-2017, 05:16 AM
jefferson3
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Not sure if this could be contributing, but the 8.8 pinion is 2-3/16" offset horizontally. I know that most people don't seem to notice any issues, but when I bought my 8.8 that was under another YJ before mine its perches were welded slightly offset so that the pinion was brought a little closer to center. I use a wheel spacer on one side to even things out.
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post #12 of 35 Old 04-24-2017, 08:44 AM
NW4wheeler
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No I got the driveshaft directly from the builders unless they f'ed up then the driveshaft should be good.
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post #13 of 35 Old 04-24-2017, 08:47 AM
NW4wheeler
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I know about the pinion off set and it would be nice to hear what other people are feeling. Because I'm not going to run a spacer on just one side I'll upgrade axles if I have to. I just want this thing to be good at 60mph and like this it feels like it's going to take out bearings.
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post #14 of 35 Old 07-27-2017, 09:19 AM
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Zombie posting on my first post in this forum but I'm hoping to get an update (and there has been some recent questions asking for an update as well)... so I think I'm in the clear

I've found that there are a bunch of us who have a very specific vibration, typically described as a "pulse" that starts in the rear of the Jeep and works forward. The pulse usually becomes noticeable at around 55-60 mph. It is very much driveline related, but not your typical rumble or high-frequency shake common with pinion angle issues, worn u-joints or excessive u-joint working angles. In my case, the pulse typically lasts for 1/2-second and is roughly 1-second dwell between each pulse (at ~60 mph). As speed increases, the pulse itself stays roughly 1/2 second long but increases in audible noise and feeling in the seats/floor (the noise is a deep "Bvvoooom", kinda like a subwoofer playing a low frequency sound that ever so slight increases in pitch towards the end). As speed increases, the dwell time between each pulse decreases. Eventually, as in the case of my 95 YJ with 4.5" REE lift, the pulses tend to merge into one another and will compound upon each other. Mine does it so bad that it triggers the knock sensor momentarily. I can muscle the engine through the pulse peak, whereas speed continues to increase (pushing 75 mph here), the pulses will separate again. By 80 mph, my pulses are very noticeable in intensity, but have the same 1-second dwell time between each pulse as at 60 mph.

I believe that the general higher-frequency vibrations, i.e. those from torsional and transverse vibrations, are very different than the oscillating, back-and-forth type of pulse-vibration that I (and many others in this thread) are experiencing. From my research so far, the people who have the most issues and describe this low-frequency "pulse" most often have the following in common:
- 4"+ of lift
- SYE/CV combo
- Deeper Gearing, usually 4.56 and up (numerically) - typically owners will notice the pulse immediately after a regear (>90% of the time)
- 4.0L (more often than not, though there are a small number of 2.5L Jeeps with a similar issue, though they usually have much deeper gearing, 4.88 or 5.13's).

For the record, no one that I have found has had this issue with 4.10 gears and lower (numerically). I have also not seen this issue with anyone running a standard slip-yoke rear shaft.

This problem has been bothering me for a few months now. Initially I was just pissed and figured it was just my luck. I went through a full list of "it's probably this" or "you need to fix your pinion angle" comments before I started to notice that others had very similar and specific issues. In my initial attempts, here's what I tried so far (in order):

- Ensured it was the rear driveline causing the issue and removed the front DS.
Result: No change in pulse, though I did note a decrease in vibration. I tracked it down to a loose pinion bearing preload in the front, so I took the front end apart, checked pinion bearings, adjusted shim pack and installed an Aussie Locker while I was there. I also had Adam's Driveshaft make a new front shaft as my slip yoke was shot!

- Installed RE 2.5 shims to bring my -2.8 of pinion angle back down to near 0 (running Ford 8.8 with AA SYE and Adams DS)
Result: No change in pulse or high-frequency "mirror shake"

- Flipped the above 2.5 shims above around to give me a VERY negative pinion angle to see if it did anything.
Result: Some rumble at take off but nothing severe; no change in pulse or mirror shake

- Tried different shims, adjusting from -4.0 to +4.6 in relatively small increments
Results: No difference in pulse or mirror shake

- Loosened and then retorque all suspension components such as leaf springs, u-bolts, etc.
Results: No difference in pulse, but did confirm everything was nice and tight

- Rotated wheels, had DS checked locally, rebalanced wheels, checked runout on rear rotors, swapped rotors, etc.
Results: No difference in pulse or mirror shake

- Checked and replaced engine and transmission mounts
Results: No change in pulse, but perhaps a very slight improvement in mirror shake (the mounts were in good visual shape, but had cracks and were very hard, though squishy).

- Checked torque on SYE yoke, loosened and retorqued to 150 ft-lbs.
Result: No difference in pulse or mirror shake

- Checked runout of SYE yoke and driveshaft; replaced SYE yoke with new, Adams' DS supplied unit
Result: No difference in pulse, perhaps a minor reduction in mirror shake. I took a week off from life and went to Mexico with the wife and kiddos; I didn't do a "before" drive to recalibrate my Shake-O'-Meter, so the reduction may be hard to say if true with absolute certainty. James (as in James Adams) did say that there were some reports of the India-made SYE yokes supplied in the Advanced Adapters kits that have been found to be out-of-round/concentricity. He was kind enough to send me a yoke free-of-charge to test out.

- Added a 1" T-Case drop I had leftover from my frame swap
Results: Extreme vibrations at take off, up to 25 mph; couldn't shift into 2/4/R; Pinion angle was measured +5.0. I could not test if this helped pulse. Obviously, a very improper pinion angle!

- Replaced new motor mounts with Brown Dog Off-Road 1" MML
Results: Eliminated mirror shake completely! However, did not reduce or affect pulse in any way. For those interested or curious, the 1" MML reduces u-joint working angle about 1.5. My current u-joint working angle at the pinion is 0.3.

- Replaced harmonic balancer and fan clutch. The rubber in the balancer was being "squeezed" out of the center hub, and it was going to get replaced anyways so I thought it would be good to see if it had any impact on my pulsing.
Result: No change in pulse, but I did notice my water pump had a small weep, so I swapped that out and did a complete system flush, while adding a Fail-Safe t-stat at the same time.

- Rotated driveshaft relative to slip yoke to see if there was a specific phasing that eliminated the pulse.
Result: No change in pulse or NVH I could notice (suggesting that phasing isn't an issue with CV shafts as much as it is with single cardan shafts).

- Rebuilt NP231 after discovering some chain slack/drag in the case (used it as an excuse to add a NP241 6-pinion planetary and 231HD wide chain!).
Result: No change in pulse.

It is driving me nuts that I cannot get this figured out, especially as summer has peaked and the nicer riding months are just a few weeks away (I'm in Phoenix AZ, so we welcome October ). My next steps are to install a JB Super Short SYE and then I have 2 options: 1) Extend the current DS out a bit and see if that helps or 2) Replace CV shaft with extended, single-Cardan style shaft (which will require cutting off my perches and rewelding a new set on).

After discussions with engineers who specialize in drive/crank shafts in large industrial applications, we believe the issue is a weird harmonic exacerbated by the relatively short shaft with a high weight-to-length ratio. I could rebuild my shaft to be lighter or stiffer as this is what really impacts resonance of shafts, but there isn't a very significant difference in weight between 2" x 0.120" vs 2.5" x 0.083" vs 3.0" x 0.083" tubing when the driveshaft tube itself is only 5" long!

FWIW, I have found only one case where a person was able to resolve this issue. He installed a single-cardan shaft with slip yoke similar to the front shaft. His TJ was then smooth as butter!
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95 YJ, 4.0L 5-spd, REE 4.5", 33", Ford 8.8, 4.88 gears, Aussie Front, 1" Daystar BL
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post #15 of 35 Old 07-27-2017, 11:41 PM
NW4wheeler
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Have you checked your rear axle bearings? I still have not found out what my vibration is. But I'm starting to think its actually the driveshaft. I've gone through everything else. Also I have friends with the same 8.8 swap as I do with absolutely no vibration and they have more lift then I do. So I can say without a doubt there should be no vibrations at all up to 80mph.
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