Vibration due to Uneven Coated Shaft?++Famous Clunk Solved (1 Viewer)

abuck99

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I just solved my vibration that started after AHC delete. Chased the same vibration for a month or so. Came down to SIDE MOUNTING BOLTS on the DIFFERENTIAL MOUNTING BRACKET. The FMS suggests 50ft lbs. Set mine to 42ft lbs and my 100 is back to Cadillac smooth. There’s four 18mm bolts that go through the differential mount and the frame. If they are too tight, the vibration from diff. is unable to dampen and is sent through the entire chassis. Hope this helps.
Are you speaking of the No. 3 Frame Cross Member mounting bolts (diff drop bracket)? Not sure how the bolt mounting torque would affect your vibration unless the diff drop bracket was fabricated poorly/out of spec and deformed further under the added torque of the driveline flex.
Screen Shot 2021-02-26 at 11.48.31 AM.png
 
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Are you speaking of the No. 3 Frame Cross Member mounting bolts (diff drop bracket)? Not sure how the bolt mounting torque would affect your vibration unless the diff drop bracket was fabricated poorly/out of spec and deformed further under the added torque of the driveline flex.
View attachment 2597060
That’s the one I’m speaking of. Not sure why torque made such a big difference. Seems like a reasonable explanation to me seeing it’s where it bolts to the chassis. Over tightening seemed to not allow the vibration to dampen. But your guess is a good as mine.
 
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Well, today I discovered an internal leak from my front ARB air locker, its discharging the air from front diff breather, pipe from compressor to diff is fine, defiinitely inside. So I'll open it and I ordered all front diff bushings from dealer in order to put diff back in with new OEM bushings.

And then, while I was coming back home, I realized that "famous clunk" which occurs while applying throttle as vehicle is coasting, disappears when I lock centre diff. Hmm..... Open centre diff causes clunk, locked centre diff does not. What happens is, when both shafts turning at the same speed, it does not clunk. When they are independant to deliver power to their diffs (front-rear), it does. And also, it does not clunk from R to D when CDL locked. That clunk is really annoying, it shakes the whole car, somehow I will solve it whatever it costs.

Additional info, when I gently start moving from a stationary position, vehicle starts moving, after 1/4 second I get that clunk from drivetrain. It does not clunk first then starts moving. Why I'm telling this, if it was a gap in front diff gears, or rear (cant be CV or hub they are brand new) where I'm searching and feeling the problem, it would first clunk and then starts moving. Because, from the perspective of open centre diff, it would be easier to fill the gap in front diff via transmitting the power to front shaft, after it fills the gap, faces the resistance, then vehicle should be moving. Am I wrong?


Another option is removing the front driveshaft but "CDL+no clunk" says that I am %100 sure that it wont clunk when I remove the shaft.

If its my front diff bushings, why does it not clunk CDL locked? If both the shafts locked and turn at the same speed, is it delivering power much smoother to diffs? At this point my diagnosing skills are insufficient.

Or should I search the source of clunk centre diff mounts or etc...?

So could you please share your experiences about "clunking with open centre diff, not clunking CDL engaged."


Edit: After giving some search efforts and thinking, clunk means I have gap somewhere maybe front maybe rear. CDL locked no clunk means I have this gap at only one side of the car, cant be both. Why I am thinking like this, if the gap is in front, CDL locks the tight rear side and loose front cant deliver power further to clunk. I rebuild the front end, CV axles, hubs, bearings etc... so this thoughts directing me to rear end....?

But this contradicts with my theory that it should first clunk and then start moving, when CD is open...

I feel I am so close to find it, it maybe the cause of my vibe issue.
 
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abuck99

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"Additional info, when I gently start moving from a stationary position, vehicle starts moving, after 1/4 second I get that clunk from drivetrain. It does not clunk first then starts moving. Why I'm telling this, if it was a gap in front diff gears, or rear (cant be CV or hub they are brand new) where I'm searching and feeling the problem, it would first clunk and then starts moving. Because, from the perspective of open centre diff, it would be easier to fill the gap in front diff via transmitting the power to front shaft, after it fills the gap, faces the resistance, then vehicle should be moving. Am I wrong?"

Condition: when fully stopped and you let off the brake and before applying throttle you then get a "thud" this is mainly due to worn bushings in the rear upper & lower control arms.
 
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"Additional info, when I gently start moving from a stationary position, vehicle starts moving, after 1/4 second I get that clunk from drivetrain. It does not clunk first then starts moving. Why I'm telling this, if it was a gap in front diff gears, or rear (cant be CV or hub they are brand new) where I'm searching and feeling the problem, it would first clunk and then starts moving. Because, from the perspective of open centre diff, it would be easier to fill the gap in front diff via transmitting the power to front shaft, after it fills the gap, faces the resistance, then vehicle should be moving. Am I wrong?"

Condition: when fully stopped and you let off the brake and before applying throttle you then get a "thud" this is mainly due to worn bushings in the rear upper & lower control arms.


Yes, UCA LCA was in my list and fitted brand new ones... I actually dont get it after releasing brake, it comes after movement with throttle applied.
 
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Today I removed the front driveshaft out and took it for a test ride. Clunk gone, vibration still there.

I am pretty sure that vibration is caused by rear driveshaft or maybe due to its joint angle to diff. Most of you were right, we caught it, thanks for that.

While front shaft was out, I experienced no clunk, so I took a look to that under the vehicle. There's the video, its being a bit off topic so I'll post it to official clunk thread as well.

 
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Today I removed the front driveshaft out and took it for a test ride. Clunk gone, vibration still there.

I am pretty sure that vibration is caused by rear driveshaft or maybe due to its joint angle to diff. Most of you were right, we caught it, thanks for that.

While front shaft was out, I experienced no clunk, so I took a look to that under the vehicle. There's the video, its being a bit off topic so I'll post it to official clunk thread as well.

So what do you think that translates to? Suppose the problem could be anywhere from TC, to front diff, to cvs and hubs.

I just came from the clunk thread and right as I was making my peace with dealing with the clunk, I am now hell bent on figuring it out =]

I think there is a connection between the clunks that people get from shifting out of park and coming to a stop ( most likely DS or bushing related based on driver reports) VS the clunks some drivers get when letting off gas and getting back on it, but go away once CDL is locked ( possible internal gearing worn rather than a drive shaft issue )
 
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So what do you think that translates to? Suppose the problem could be anywhere from TC, to front diff, to cvs and hubs.

I just came from the clunk thread and right as I was making my peace with dealing with the clunk, I am now hell bent on figuring it out =]

I think there is a connection between the clunks that people get from shifting out of park and coming to a stop ( most likely DS or bushing related based on driver reports) VS the clunks some drivers get when letting off gas and getting back on it, but go away once CDL is locked ( possible internal gearing worn rather than a drive shaft issue )

I actually added a video to the post that you quoted. But probably its not appearing. I think its front diff. I will open it.
 
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I think there is a connection between the clunks that people get from shifting out of park and coming to a stop ( most likely DS or bushing related based on driver reports) VS the clunks some drivers get when letting off gas and getting back on it, but go away once CDL is locked ( possible internal gearing worn rather than a drive shaft issue )


Here I am trying to tell what I understood with my broke English, hope I can...

The reason why CDL erases the clunk, its because driveshafts can not spin freely. Assume that front diff has more play than rear, and shift it to D, centre diff will transmit power to both shafts until they will fill the gap, if one of them has execessive play, it clunks. Because shafts are free.

But when you lock CDL, which means shafts are equal now, and we assumed that our rear diff has no excessive play, and rear shaft will face the resistence earlier then the front, so when rear stop after filling the factory gap, front one cannot go more to clunk, cuz they are locked.

Thats what I understood after giving effort today under the vehicle, removing shafts, using pry bars, giving test rides with one shaft removed etc.....


Edit: are you able to watch the video, if not, I will find another way to upload.
 
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Here I am trying to tell what I understood with my broke English, hope I can...

The reason why CDL erases the clunk, its because driveshafts can not spin freely. Assume that front diff has more play than rear, and shift it to D, centre diff will transmit power to both shafts until they will fill the gap, if one of them has execessive play, it clunks. Because shafts are free.

But when you lock CDL, which means shafts are equal now, and we assumed that our rear diff has no excessive play, and rear shaft will face the resistence earlier then the front, so when rear stop after filling the factory gap, front one cannot go more to clunk, cuz they are locked.

Thats what I understood after giving effort today under the vehicle, removing shafts, using pry bars, giving test rides with one shaft removed etc.....


Edit: are you able to watch the video, if not, I will find another way to upload.
Great information , thank you. I do see the video now but will watch closer when I am on my computer .

I guess the next question would be do we care about this play in the differential, should it be considered normal with our trucks ? If a fluid change doesn't show any metal chunks then my thought is to just let it go until it gets really bad before a rebuild.
 
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Did you grease the shafts after installing?

I see a lot of people who don't grease them which results in a clunk at takeoff
 
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Great information , thank you. I do see the video now but will watch closer when I am on my computer .

I guess the next question would be do we care about this play in the differential, should it be considered normal with our trucks ? If a fluid change doesn't show any metal chunks then my thought is to just let it go until it gets really bad before a rebuild.


For now I advice you not to touch it. I will leave it to a professional shop and tell them to adjust the front diff if possible, if not put new gears and also fix the leaking air locker, and will put it back with new OEM bushings, and will tell you that fixed or not. If that fixes then you may do it. Here where I live it won't cost too much but I can understand in the States these things are expensive in terms of labor. Though, cars are expensive here in comparison to US :)
 
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Did you grease the shafts after installing?

I see a lot of people who don't grease them which results in a clunk at takeoff

No I didn't cuz they were already greased, rebuilt with new U-Joints, balanced etc... I am %100 sure clunk has no relation with shafts, in my case. But I am also %100 sure that my car vibrates slightly due to dents or coating on the rear shaft.
 

94SRUNNER

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No I didn't cuz they were already greased, rebuilt with new U-Joints, balanced etc... I am %100 sure clunk has no relation with shafts, in my case. But I am also %100 sure that my car vibrates slightly due to dents or coating on the rear shaft.
Would it be possible to pull the shafts and have them use an sand blasting type technology to clean the coating off, taking care to protect the sensitive parts?
 
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Would it be possible to pull the shafts and have them use an sand blasting type technology to clean the coating off, taking care to protect the sensitive parts?


Yes sure, I was just wondering which one was causing that vibe. You know we feel one problem and start throwing money at it, I just don't want to do it anymore, ensuring the cause should be main objective. In this forum I spent hours and hours about that clunk and vibration thing. There are millions of reasons but we just cannot replace everything at drivetrain.

My problem; clunk+vibration. I suspected CV axles, hub flanges, UCA+LCA and some other etc.... One of my CV boot was shot, UCA boots were totaled, blabla... so I dont feel much pain about replacing them but no more waste of money, I should stop replacing parts on assumptions.

What I did, took the front shaft out, drove it. Vibe is there, clunk gone. So clunk related to front diff, vibe related to rear. I am also thinking about rear shaft angle, I am pretty sure that I am very very close to solve these problems and enjoy the vehicle. But being impatient and replacing parts on assumptions is really waste of money and time.
 
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Update on vibration issue;

Today I took the rear driveshaft out of the vehicle, and drove a test. I reached up to 135 km/h (85 mph) and no vibe... Before I also did drive the vehicle without front shaft, vibe was there but clunk was gone. Before I already checked the front diff free play (video post #46) which was a lot, today I checked the rear diff free play, its like hair thin, which is factory I think.

So today I am definitely sure that my rear shaft has balancing problems.
And clunk thing caused by the excessive gap in front diff.

Another thing I realized, at some certain speed front diff is whining, which tells me a lot about official clunk thing. :)

Next week, I will start cleaning and rebalancing the rear shaft and open the front diff in order to fix the leaking air locker and re-adjust the gap in between ring and pinion.

The dramatic free play difference in between the front and rear differential is probably caused by being AWD and front wheels steer. Also you may find it silly but I think that very very common clunk thing may be caused by resistence difference. Somehow most of our 100's eating the front diff earlier, maybe because of the weaker design of front diff and steering is another stress, and the resistence different I mentioned.

By that resistence difference I mean; front diff is closer to transfer case and uses a shorter, lighter shaft. MAYBE (lynch me If I am wrong) it's somehow being easier to transmit much power by a hair to front diff in comparison to rear. After long years and kilometers that occur.
 
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Finally, I took the front diff apart... Inside, it was not disaster actually. Yes there was a bit of free play but it was not that bad. To sum up what we did is;

-Renewed the leaking ARB air locker with its rebuild kit after 10 years. This is the worn part.



-Gears, bearings were all fine, no broken gear, acceptable metal shaving on the drain magnet. Put it back together, did the adjustment with gear paint, set to factory gap, and pray for not to whine :)
Some pics.






Then I just did not want to put it back with old factory bushings, they were shot. The one located on the diff cover is pain in the ass to remove. But somehow we did it, heater gun, hammer etc... Did it.







And some extras, my LC100 has ARB OME and they are 10+ years old, I took the front suspensions in order to inspect their bushings, and what happened is, loosened suspension bolts, grabbed it to pull out, then bushings inner metal tube fell on ground :) Toast.




Another thing, on bumpy roads, I had a clicking noise coming from steering column, I grabbed it and shaked, nearby the brake/gas pedals, it was definitely column upper bearing. So took'em apart, tons of cables, switches, wiring, narrow place to work in etc.....

Finally got it and took it to a metal works shop where they have advanced lathe machines, they replaced the shot bearing. Put back, tight as rock!

Problematic little bearing can easily be seen on second picture.






Finally, smoother front end, tight, no gap, no play, no sound.

Vibration still there at highway speeds, its the next and final thing to solve. I'll keep posted.
 
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Finally, I took the front diff apart... Inside, it was not disaster actually. Yes there was a bit of free play but it was not that bad. To sum up what we did is;

-Renewed the leaking ARB air locker with its rebuild kit after 10 years. This is the worn part.



-Gears, bearings were all fine, no broken gear, acceptable metal shaving on the drain magnet. Put it back together, did the adjustment with gear paint, set to factory gap, and pray for not to whine :)
Some pics.






Then I just did not want to put it back with old factory bushings, they were shot. The one located on the diff cover is pain in the ass to remove. But somehow we did it, heater gun, hammer etc... Did it.







And some extras, my LC100 has ARB OME and they are 10+ years old, I took the front suspensions in order to inspect their bushings, and what happened is, loosened suspension bolts, grabbed it to pull out, then bushings inner metal tube fell on ground :) Toast.




Another thing, on bumpy roads, I had a clicking noise coming from steering column, I grabbed it and shaked, nearby the brake/gas pedals, it was definitely column upper bearing. So took'em apart, tons of cables, switches, wiring, narrow place to work in etc.....

Finally got it and took it to a metal works shop where they have advanced lathe machines, they replaced the shot bearing. Put back, tight as rock!

Problematic little bearing can easily be seen on second picture.






Finally, smoother front end, tight, no gap, no play, no sound.

Vibration still there at highway speeds, its the next and final thing to solve. I'll keep posted.



Nice work, it is cool to see the progress you are making.
 
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Finally, I took the front diff apart... Inside, it was not disaster actually. Yes there was a bit of free play but it was not that bad. To sum up what we did is;

-Renewed the leaking ARB air locker with its rebuild kit after 10 years. This is the worn part.



-Gears, bearings were all fine, no broken gear, acceptable metal shaving on the drain magnet. Put it back together, did the adjustment with gear paint, set to factory gap, and pray for not to whine :)
Some pics.






Then I just did not want to put it back with old factory bushings, they were shot. The one located on the diff cover is pain in the ass to remove. But somehow we did it, heater gun, hammer etc... Did it.







And some extras, my LC100 has ARB OME and they are 10+ years old, I took the front suspensions in order to inspect their bushings, and what happened is, loosened suspension bolts, grabbed it to pull out, then bushings inner metal tube fell on ground :) Toast.




Another thing, on bumpy roads, I had a clicking noise coming from steering column, I grabbed it and shaked, nearby the brake/gas pedals, it was definitely column upper bearing. So took'em apart, tons of cables, switches, wiring, narrow place to work in etc.....

Finally got it and took it to a metal works shop where they have advanced lathe machines, they replaced the shot bearing. Put back, tight as rock!

Problematic little bearing can easily be seen on second picture.






Finally, smoother front end, tight, no gap, no play, no sound.

Vibration still there at highway speeds, its the next and final thing to solve. I'll keep posted.
Vibration....Transfer case rear shaft output bearing?
 
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Vibration....Transfer case rear shaft output bearing?

You can be very right.

Considered already on many possible things, I am doing my list for that. What I have in my hands is, without rearshaft, does not vibrate. Shaft balanced trillion times, by different shops, experts, I even took it to a factory where they build Ro-Ro shafts :) All say its something else not the shaft itself.

Rear bearing at centre diff, also the bearing at rear diff etc... but I do not open things till I believe %99 problem is there. Another thing I realised, pinion angle things. I measured the height difference in between the front and rear fender well, its approx 6-7 cm (I think its approx 2.5 inches) I do not know the exact factory "should be" difference but a friend of mine has a bone stock LC100 without AHC from factory. I just called him and parked vehicle next to mine and measured, compared many things. (heights, angles, control arm angles etc....) mine might be raked a bit much. First start with cheap, I'll remove the plastic round shaped thing whichs put up on the rear spring by previous owner, then give a try. If that fixes, I'll get new springs cuz the ones on the vehicle are may oversqueezed. If that not fixes, I'll borrow rear shaft, give a try. Not fixes again, its time to aim on diffs :)
 

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