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burnt_servo

vibration at 80km

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so this might be a bit long  , please bear with me .

working of a 2001.5 quadcab 4x4 diesel 2500 automatic ( single piece rear drive shaft ) less than 150,000km

I'm getting vibration around 80km +/- 10-15 km ( starts around 70km , goes away over 100 km )

it feels like a drive shaft or bad u joint . ( but drive shafts are good )

started off with swapping the rims and tires over to another balanced set ( both sets of wheels where clean , no mud , and weights where in place ) .... vibration still there

went through the rear diff and rear drive shaft , all good , replaced rear  brake pads and joints in drive shaft ( joints where still good )..... vibration still there

went through front axle , ended up replacing upper and lower ball joints ( lowers where wore out ) , brake pads and put a lukes link in track bar .

wheel bearings are good , u joints next to wheel bearings also good .

tie rod ends are tight , track bar really didn't need the lukes link . previously installed a steering box brace ( steering box is still tight ) ....... vibration still there , but less intense .

removed front drive shaft ..... vibration still there without front drive shaft  ..... rebuilt the entire shaft , 3 u joints and centering pin joint .( it needed it ) . put front drive back in , and no change in vibration .

put truck on axle stands and could not get it to vibrate while powering the drive train ,even spun everything up to 180ish km ...nothing .

I had previously installed a switch to lock up the torque convertor , the vibration becomes more noticeable while locked , but I am assuming that is due to the lack of damping effect when the convertor is locked .

switched out the harmonic damper on motor , things got smoother , but I think this was due to the balance holes in damper filled solidly with gunk . the original damper was in much better shape than the spare I put on .

I also changed the rear drive shaft out to my spare , thinking it might be a balance problem on the shaft ..... it made no difference .

vibration does not change with engine rpm , only changes with vehicle speed .

it also becomes slightly less severe when you  lift the throttle .

 

any ideas ?

 

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1 minute ago, burnt_servo said:

feel exactly like a dry , slightly worn u joint cup would .

Hoo boy.  Thats a tough one then.  There are only 28 U joint cups on the truck.  U joint wear can be hard to find until they start grinding.  

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after doing a bit more digging I've come up with a couple more things to chase down once it warms up a bit .

the tail shaft on the transfer case  could be worn enough that the one end of the drive shaft is essentially spinning in a larger circle and

dynamicly unbalanced .

the other thing that might be happening , and worn transmission mounts would makes this worse , the springs could be settling enough and the pinion angle could be in a slightly more lifted position from stock . 

6 minutes ago, CSM said:

Hoo boy.  Thats a tough one then.  There are only 28 U joint cups on the truck.  U joint wear can be hard to find until they start grinding.  

and I have replaced all but 2 of them , and the 2 left alone where very closely examined .

 

what I'm thinking now is a worn tail shaft would cause a similar type of unbalance .( the drive shaft turns a larger circle than it is supposed too , a worn dry cup would do something similar ..... in other words the dynamic centerline of the shaft isn't the same as the static center line  ) .

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it isn't leaking , but I am going to see if I can swap the tailshaft out  from my parts truck .

I'm running out of things that might be the issue .

also the part number is this 18172 .

type " 18172 bushing " into google and that is the bushing .

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sure sounds like a drive shaft problem, but i had it happen once that rear drums were warped so bad it was shaking driving down the road. might try to rotate tires and see if vibration moves to a different spot could be something with rims or tires. 

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I checked the run out on all 4 of the brake rotors and they seemed good , checked the wheel bearings front and rear and even set the rear wheel bearings  up with a torque wrench .

also no change  in vibration  with 2 different sets of rims and tires .

 

when I pulled the rear tail shaft out my parts truck I measured the angles of the shaft in the transmission and the pinion ..... now this is on the parts truck .....with the angle finder zero'd on the transmission , the pinion was 2.5 degrees high ( high as in away from the ground ) ...... it should be 0 or 1 degree low ( as the pinion will lift under acceleration , this is according to the shop that balances drive shafts ) .

if you take the zero off of the pinion , the end of the tail shaft is 2.5 degrees low .( the transmission needs to be lifted )

so pretending that the transmission  mounts do settle with age , it is entirely possible this the issue .

the more I google this , the more I am seeing this as a issue that is either unsolved or has many possible solutions .

 

I have a bushing and seal coming in tomorrow , so I didn't get too  carried away with my truck today .

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Arrg,  Sorry burnt!  Missed this, was gone all weekend!

Hope you get it straight!  What I surmised my problems to be, with the tailshaft bushing going,  the splines are designed to transmit torque, NOT center the yoke. (The bushing is supposed to center it,  the output shaft of the TC is almost "free" in that direction)  So the shaft can move eccentrically.   I am not sure why this shows up worse on some vehicles and others not at all.... 

I have had trouble with the "location" of the carrier bearing...  like the slop in the holes makes a difference....  on an early S10, The driveshaft would vibrate unless you had the carrier put back in JUST the right spot....  I never could explain it.  (I have a center post lift, so I could never see what happened easily while it was loaded, so maybe something moved funny.)

Hag

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it has been -20 here the last few days , today it warmed up to around -5 , so I started tinkering .

 

the bushing I got was the wrong size . not sure if the part number is wrong , or the part was mixed up with a bag with the right part number on it .

so I measured the clearances on my parts truck and my truck .

parts truck , 8 thou clearance between yoke and bushing .

my truck , 13 thou clearance .

so I installed the parts off of the parts truck , and the vibration was cut in 1/2 .

 

as for drive shaft angle .

zero'd it out on the tailshaft , then measured the pinion angle , and the pinion is 0.2 degrees down ...... which is almost perfect .

 

so what is left ? I haven't touched the mechanism the engages / disengages the front axle for 4x4 .

I'm going to get the rear drive shaft balanced just for the heck of it .

and seriously thinking about putting balance beads in the tires , again just for the heck of it .

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Burnt,

I hated to give you a part number... I couldn't find exactly what bushing I used, and there seems to be some discussion on what is really the right one. 

Here are a couple pictures.  There was some question when I was looking for my replacement, as to whether two casting numbers were use-able.  (C-16258 and C-17460) 

They are interchangeable.  The earlier design had the fluid return machined in, and the later it was just cast in.  No real functional difference. 

Yoke to bushing actual clearance numbers seem to elude everyone...  It looks like New should be  0.003"-0.004"  worn out is in the 0.008"-0.009" range.

Hope this helps!

Hag

IMG_0872.jpg

IMG_0878.jpg

IMG_0879.jpg

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i've been meaning to update this  . 

 

so i shimmed the bushing with shimstock , then pressed it into the housing , i can't remember off hand the clearance but it was tight , around 2 or 3 thou . 

i then drilled and tapped the the housing with a grease nipple , and i give it a shot of grease when i grease the other u joints . 

 

but there was still a bit of a vibration ..... and i think i figured it out today , i've had a 216 error on my injection pump for a while , this controls timing advance . well now  right when the vibration would normally appear , the engine is starting to misfire slightly .... the vp 44 isn't long for the world , but i strongly suspect it was doing this before , undetectable , but just enough to set up a harmonic  to create a vibration  . 

 

i'll know when i finally get the new vp44 installed 

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