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4WD High vibration


jjonez
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Happy Sunday folks.  I was hoping to get some suggestions on this.  I get a bad shake/vibration from the front end when in 4hi (tested on pavement going straight). It is the worst when accelerating/under load in gears 3 and 4 (haven't tried 5) but is still present when cruising or coasting.  Here are the scenarios i tested for narrowing this down:

 

2WD w/ both hubs unlocked: no issues

4HI w/ both hubs unlocked: no issues

2WD w/ one or both hubs locked: slight vibration any speed above 50 mph, but not terrible

4HI w/ one hub unlocked: seems smooth, but I still need to test above 50 mph

 

Parts I've checked:

 

Front driveshaft: rotates freely by hand; good end play; U-joints seem solid

CV axles: steep angle from the lift, but both rotate freely by hand

Tires: same model/size and I rotate them regularly

Diff mounts: There is about 1/4" of play in the rubber bushings on both sides when I push up on the rear of the diff (flange where U-joint connects)

Wheel bearings: they do have some play and make a little noise on low speed tight turns

 

So far diff mounts and wheel bearings are all I've identified as potential culprits.  But the bearings I'm not so sure about since the ride is smooth in 2WD/hubs unlocked.  I'm considering buying a knockoff go-pro to stick under there and see if it reveals anything.

 

I'm probably missing something, as usual, so any suggestions before I start replacing stuff?  Thanks for the assistance as always!

 

JJ

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Take a look here:

Rumble and Shake in 4WD?

https://r.tapatalk.com/shareLink?share_fid=45554&share_tid=43858&url=http://www.nissanpathfinders.net/forum/index.php?/topic/43858-Rumble-and-Shake-in-4WD%3F&share_type=t

 

Just in case you want to give it a good read, I was having the same issue as you for a long time, and that’s my thread on it. It was a very large discussion, so reading through all of it might take some time, but I ended up posting my results and fix, analysis, and all that in the final post.

I even used a go-pro under the chassis to find the problem myself, and unfortunately, the result only lead me astray.

 

Like I said, read through it, we really touched on every possible option for what would cause the issue. There’s 132 replies worth of information and troubleshooting, so get a list ready!

 

Good luck!

 

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Also, if you have the time and a good press, changing those Differential Mount Bushings really doesn’t hurt. I did that and I’m glad I did, makes it feel a bit more controlled in 4WD. Originally I could move the diff up and down by hand by pushing up on the pinion side, so it was time to be done anyways haha.

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Thanks Quasar, I followed your thread while it played out. While I do rotate my tires regularly, I use the rearward cross pattern so the fronts and rears always swap in tandem.  I suppose if one set wore faster than the other I could run into the same issue you had and it wouldn't get resolved by rearward cross rotation.  I'll check the tread depth and probably swap one front and one rear regardless of what I find to see if it helps.

 

My main doubt is the fact that I still get a slight vibration in 2WD with the hubs locked.  In this case tire tread depth differences shouldn't matter right?  Since the front driveshaft can rotate independently of the rear.

Edited by jjonez
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Sounds like you've got a pretty good idea of what needs doing already. Even if your tire sizes are identical, if your wheels are anything but dead straight while you're driving in 4H on pavement, you're still winding up the transfer. If your diff is sagging, the U-joint angle could be just wonky enough to vibrate a little when it's spinning but not under load, then get wonkier (and noisier) when loaded.

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Correct, the only time it would REALLY matter is with the tcase in gear, as it requires that near-perfect 1:1 between the front and rear.

How bad is your CV angle? More important, have you done an SFD? I’ve been able to go smooth on 2.5” of lift in comparison to the subframe (and by that I mean I had 6.5” spacers, but only a 4” SFD. That’s changed now) without any major vibration in the CVs. So we’re good there.

Have you looked for play in the driveshaft flanges? Specifically to the transfercase? I’ve heard of cases where the bearings are shot to the output flange and it causes a bunch of balance issues.

Sounds like you've got a pretty good idea of what needs doing already. Even if your tire sizes are identical, if your wheels are anything but dead straight while you're driving in 4H on pavement, you're still winding up the transfer. If your diff is sagging, the U-joint angle could be just wonky enough to vibrate a little when it's spinning but not under load, then get wonkier (and noisier) when loaded.


This is also a good point. A U-Joint setup requires similar angles on both ends of the shaft for it to operate smoothly. If one end is too high or at an extreme angle, it’s gonna be a rough ride.


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Hmmm.. yeah that slight vibration in 2H with hubs locked makes me suspect the CVs.

How are your CV boots? If you’ve already got a small crack then try pumping them slap full of grease.

I use this for mine:
94a445a5789814e07b04836c0ba6fa0f.jpg

My boots are ripped up but I slam them full of grease every 5k miles and they’ve been going for years like that now.


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My boots are ripped up but I slam them full of grease every 5k miles and they’ve been going for years like that now.


Oh god, I had a small hole about a centimeter across in a boot once, and the mess it made from the grease was horrendous. I cant imagine the mess if they were pumped full :O


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Oh yeah it slings grease for sure but it washes off with a power washer. The underside of my vehicle is a dirty dirty place.. my leaking rack coats everything all the way back to the transfer case with a layer of oil. Rust protection. :]

If the vibration is coming from his CVs then packing them with grease can temporarily reduce the vibrations. It’s like over packing a worn electric motor bearing to buy time until you have the replacement.

If you do pack your CVs then the thicker the grease the better. It wont stop the vibrations for very long and you can repack them again to confirm. And Quasar is right, it’ll be a mess.


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Thanks for the replies guys.  So I measured the tread depth in multiple locations and only got about 0.5 mm difference front to back.  I'm going to swap around a front and rear tire but Im not getting my hopes too high for this to solve the issue, since Quasars we're about 3 mm different.

 

I inspected the front driveshaft again.  There is some VERY slight play in the Tcase flange compared to the diff flange which has none.  Also, the piece on the shaft that is closest to the Tcase but still rotates with the shaft (dust cap?) is not seated evenly, not sure if that matters.

 

Also also, when I rotate the shaft I can feel both U-joints articulate slightly, so I guess the diff/Tcase aren't perfectly aligned?  Though that's what U-joints are for right?  But still, could be the sag from the mount bushings I guess...

 

The CV angles are pretty steep.  OME HD coils and a 1" spacer so maybe 2.5-3" of lift and no SFD.  At least one of my CV axles is from the junkyard, can't remember about the other.  There is a tiny tear in one (on the edge where the boot doesn't flex) that I covered with RTV and it's held up so far.  The underside is surprisingly clean, I hope to keep it that way so I'll save the grease pumping for when I'm really desperate haha.

 

I hope it gets resolved.  The truck is a joy to drive with the new suspension and has held up amazingly well for being 16 years old with 150k miles.  Sucks to have it spoiled when trying to use it like it should be.

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Well let’s talk about the vibration characteristics. How would you describe the vibration? Is it low frequency like death wobble? Or is it a medium frequency like the hum of your engine? Or high frequency like the roar of a wheel bearing?

When the CVs (both at same time) went bad in our old MDX it was a combination of medium frequency vibrations that waxed and waned with very low frequency and violent vibrations that increased with acceleration.

When my steering rack bushings gave out the vibrations were low frequency and could be seen in the shaking of the steering wheel side to side.

When my drivers side wheel bearing went out there was what seemed like white noise at highway speeds with vibrations that felt like traveling over ice in a sled at lower speeds.

When my control arm bushing went out is was also low frequency and extremely violent.. like shake the car so hard you can’t see straight violent.

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Definitely on board with onespiritbrain. It might be able to be narrowed down that way.

And yeah, depending on the size of your tires altogether, 0.5mm just won’t cause that much trouble due to the angular velocity and rotation of the tire, a difference of 0-0.5mm is so tiny that the differential or TCase won’t see it when it’s geared in proportion. That CV angle sounds like a bit of a flag however. Is this the first time you’ve experienced this after the lift? Did you lift it recently, and now that you’re using 4WD you notice it? Or have you had the lift for a while and this only now started?

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4 hours ago, onespiritbrain said:

Is it low frequency like death wobble? Or is it a medium frequency like the hum of your engine? 

I'd say probably in between these two.  It just borders on being a shake but still a vibration in my opinion. It's more subtle when not under load, but the intensity increases dramatically when accelerating.  Sounds most similar to your MDX.  I didn't think of the control arms, though I would expect the problem to always be present in that case.  You've had your fair share of shakes and vibes!

 

4 hours ago, QuasarDecimari said:

That CV angle sounds like a bit of a flag however.

Now that I think about it, I've only used 4hi a handful of times since the lift went on a year ago.  I first noticed the issue earlier this year on a snowy road and haven't used 4hi since.  Maybe I damaged a joint before that on a nasty road requiring 4low.  Or maybe the joints never liked the angle of the new lift and I never noticed.  Now that ski season is around the corner it's time to address it haha.

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With the MDX on cold mornings it would be smooth as butter until after driving for a while then it would start again. And after it had started vibrating badly you could blip the gas pedal and sometimes it would stop vibrating completely until you came to a stop.


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That was the case for me too. I did a bunch of mods but never used 4WD at higher speeds other than crawling on trails, so I didn’t know there was a problem until later. One of the problems with a high CV angle is that the front end lifts a little bit under torque, which causes and even more severe angle for the axles to put up with. While not enough to bind, it’s still pushing the limits of their smoothest operating range. Thats a har one to troubleshoot though.

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Alright then, I think game plan for this weekend is to go ahead swap a couple tires just to put that to bed, and while the front is in the air do a thorough inspection of every suspension component and check for bind/smoothness of the CV's at full droop.

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Alright, so today I jacked up the front and poked around.  Fortunately the the cv axles didn't bind at full droop with both wheels in the air.  However the right wheel has a couple spots of resistance when I spin it.  In addition to that, spinning the wheels/axles revealed the diff mounts to be worse than I thought.  Lots of side to side movement seen in the bushings on both sides when rotating the right wheel.  For some reason the diff sits still when rotating the left tire and keeping the right still.  My coworker spun the wheel while I filmed.

 

Video right side

 

Video left side

 

The tapping/scraping noise every 2-3 seconds is a portion of the cv boot band clamp contacting the lower ball joint stud.  Not an issue when laden.

 

So here's my thinking: I only get bad vibes with hubs locked/4Hi b/c the wheels are connected to the diff AND the diff is receiving input from the motor.  With hubs locked I get only mild vibes b/c the wheels are still connected to the shaking diff, but not amplified by torque.  When in 4hi/hubs unlocked I don't get vibes at all because the shaking diff is isolated from the wheels/suspension.

 

Quasar I know this didn't fully fix your issue when you had it, but I think new bushings is the best course of action for now since it's at least apparent that it needs to be done.  What method did you use to remove the bushings from the mounts?  I'm tempted to just by new OEM mounts to avoid hassle, based on my experience with the rear control arm bushings.  My one concern with buying rubber stuff regardless if it's the whole mount or just the bushings is the age of the "new" part.  What do you guys think about rubber parts sitting on a shelf for 10+ years?  If it's in a sealed package should it be a concern?

 

That being said, I wonder if Towndawg made any progress on his diff poly bushings...

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Oh yea, and I did swap the front left and rear right tires just to put that to rest.  It's possible it might have helped, as sometimes the vibe isn't as pronounced, but I can't say for sure since the only testing I can do is accelerate back in forth in an empty parking lot.

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Definitely swap those bushings haha, it’s going to be worth it by the looks of it (and really help narrow things down if it isn’t the fix). If you have the cash, buying the whole arm assemblies with pre-pressed bushings will save you a crap ton of work. I otherwise had to use a press and large impact sockets to get those suckers in and out of the arms. With a big press, it was easy. Never would have gotten it done without one, however.

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When I did my rear control arms I had to pay a shop to do the pressing.  Worth it for switching to poly.  But it would totally eat into the savings of just swapping new rubber bushings in this case, so the whole mount is worth it.

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