Unsolvable vibration

schulte

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Jul 31, 2010
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So this vibration started almost a week ago on the highway after I went over a bump. 2008 LMM regular cab / cab and chassis, 216k miles on it, mostly stock motor with straight pipe, deleted, tct batmowheel, fingers vanes, etc.

The vibration is very harsh in the cab, like a broken crank or worse. Wants to shake the dash apart. Now it starts when I go over a bump, especially if I hit a bump on the right side. It keeps on vibrating if I slow down or speed up, and only stops when I stop or almost stop the truck.

I've tried dropping it in neutral and revving the engine and the frequency of vibration doesn't change. I've also tried shutting off the engine and just coasting, and it still vibrates.

Driveshaft has all balancing weights intact, has relatively new ujoints, and has no dents.

Here are some videos...

https://www.youtube.com/watch?v=_aqm47_5Aog

https://www.youtube.com/watch?v=J6DrQOixWp8
 

Novak

SQUIRREL TRYN TO GET A NUT
Jun 15, 2015
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It doesn't seem like a large violent like a death wobble so I wouldn't think it was steering. Notice any leaks or seeping, Check your transfer case fluid or differential fluid?


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Novak

SQUIRREL TRYN TO GET A NUT
Jun 15, 2015
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But it wouldn't hurt to check your pitman and idler for slop in the steering components and box.


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subman1980

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Feb 4, 2013
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Sounds like death wobble. It does happen on IFS trucks, I have seen it several times at the body shop on damaged trucks and due to worn out steering parts. Get the front end in the air and check for play at 12 and 6 and also 3 to 9 position on each front tire. Check pitman and idler, tie rod ends, ball joints etc.
 

Bulldogr6

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Feb 18, 2012
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Wester Mass
Does turning affect it or happen right after? Sometimes A worn CV joint can cause a wobble feel.

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schulte

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Jul 31, 2010
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Probably the Rear end.

Jack up rear axle and put it in gear.

It's got a relatively new (10,000mi?) ring and pinion and all new bearings, and if I run it up on jackstands I don't get any vibration.

Then again, the vibration only starts when I go over a bump.
 

oscyjack

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May 7, 2016
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I'm gonna go with a shifted leaf, bad leaf bushings, or a broke spring/bolt. The again who did the rig and pinion? Could be something wasn't done properly. Is the g80 new?

CV could be it, cheap replacement. Any play in them?
 

Bulldogr6

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Feb 18, 2012
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I'm gonna go with a shifted leaf, bad leaf bushings, or a broke spring/bolt. The again who did the rig and pinion? Could be something wasn't done properly. Is the g80 new?

CV could be it, cheap replacement. Any play in them?
It's not so much a loose thing always. What happens is a grove gets worn in n the cup . Mostly happens after a turn.

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
i would suggest you lift the front end and look for worn parts. do the typical checks for wheel bearings and ball joints and steering. should be the first thing you do since we are not there to look it over
 

schulte

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Jul 31, 2010
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I'm gonna go with a shifted leaf, bad leaf bushings, or a broke spring/bolt. The again who did the rig and pinion? Could be something wasn't done properly. Is the g80 new?

CV could be it, cheap replacement. Any play in them?

I've just replaced all the leaf spring bushings.

Also just replaced the front upper and lower control arm bushings and ball joints on one side, as well as wheel hub on that side.

I did the ring and pinion; it was a new ring and pinion with full install kit (timken or SKF?), bearings, crush sleeve, etc. Preload, backlash, and pattern were all great. Installed with a new Detroit TrueTrac.
 

schulte

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Jul 31, 2010
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i would suggest you lift the front end and look for worn parts. do the typical checks for wheel bearings and ball joints and steering. should be the first thing you do since we are not there to look it over

The whole front end is a little worn, definitely some play in tie rods and pitman/idler, but nothing insane. I've seen many worse that didn't do anything like this.

Then again, maybe it's just the combination of certain parts worn more than others.
 

schulte

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Jul 31, 2010
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Just drained the transfer case, fluid was OK but definitely some shit floating around in there.

No leaks out the rear output shaft, but the transmission shifter shaft seal has been leaking for a while so the whole extension housing/front of transfer case is wet so I can't really tell if it's leaking out the front.

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schulte

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Jul 31, 2010
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Also just pulled the rear diff cover; fluid was ok with no signs at all of any metal save for a little tiny bit of black sludge on the drainplug.

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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83
Phoenix Az
The whole front end is a little worn, definitely some play in tie rods and pitman/idler, but nothing insane. I've seen many worse that didn't do anything like this.

Then again, maybe it's just the combination of certain parts worn more than others.

have you not checked since this happened? alot of what you claim points to wheel bearings or separated tire too
 
Last edited:

2004LB7

Well-known member
Dec 15, 2010
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Norcal
Also just pulled the rear diff cover; fluid was ok with no signs at all of any metal save for a little tiny bit of black sludge on the drainplug.

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shouldn't the faces of those teeth be worn in / polished shiny? looks flat and dull in the photos. how many miles on them?
 

Bulldogr6

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Feb 18, 2012
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have you not checked since this happened? alot of what you claim points to wheel bearings or separated tire too
I was thinking along this line as well like possible cracked wheel too but feel those symptoms would be more constant.


Curious ly do you have aftermarket wheels and/or a leveling kit?

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schulte

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Jul 31, 2010
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have you not checked since this happened? alot of what you claim points to wheel bearings or separated tire too

Yes I've checked since this started; definitely not tight but not terribly sloppy. All the front end parts could probably be replaced but I'm talking probably 1" or so of play at 9 and 3 o'clock.

Driver side wheel bearing was just replaced. Passenger has no play at 12 and 6 o'clock.

I've tried different tires; I was previously running aftermarket 265's on 17" aftermarket wheels (less than 15k miles on that setup) and I tried swapping over to some stock PYO's with 245's, no change in the vibration.