Bad Vibrations

[nzoliver]

Howdy all, Something to ponder.....

I have a harsh vibration under medium to hard acceleration at 55km/h (31MPH) and it comes in again at 100Km/h (62MPH). SO far we have tried this to no avail:

Remove rear prop shaft - problem stays
Remove front shaft - problem gone
Install brand new front shaft - no difference
Dissasemble and check centre diff - all just fine
Dissasemble front diff - all fine
Checked both CVs and front wheel bearings - all fine
Changed the wheels for some from another vehicle - no difference
Put the truck on a hoist and run it up to 55 - transfer case starts shaking - engage diff lock and the problem is almost gone.

Where to next??
Any clues?? It is a '98 300Tdi with 80000km.
:(

[Blknight.aus]

Howdy all, Something to ponder.....

I have a harsh vibration under medium to hard acceleration at 55km/h (31MPH) and it comes in again at 100Km/h (62MPH). SO far we have tried this to no avail:

Remove rear prop shaft - problem stays
Remove front shaft - problem gone
Install brand new front shaft - no difference
Dissasemble and check centre diff - all just fine
Dissasemble front diff - all fine
Checked both CVs and front wheel bearings - all fine
Changed the wheels for some from another vehicle - no difference
Put the truck on a hoist and run it up to 55 - transfer case starts shaking - engage diff lock and the problem is almost gone.

Where to next??
Any clues?? It is a '98 300Tdi with 80000km.
:(

ding ding ding ding ding....

WE have a winner.

Flogged, siezed or otherwise not happy UJ, slip joints flogged out or the shaft has thrown a weight and is now out of balance.

Its rare but it could aslo be the output flange on the Tcase is out of true, slopping on its splines or the front bearing is on the way out.

have fun, dont keep driving it if the UJs aint happy, thrown front propshafts Aint exactly fun.

[Graeme]

Check that the handbrake drum isn't out of round by really backing-off the shoes.

[jmkoffice]

Howdy all, Something to ponder.....

I have a harsh vibration under medium to hard acceleration at 55km/h (31MPH) and it comes in again at 100Km/h (62MPH). SO far we have tried this to no avail:

Remove rear prop shaft - problem stays
Remove front shaft - problem gone
Install brand new front shaft - no difference
Dissasemble and check centre diff - all just fine
Dissasemble front diff - all fine
Checked both CVs and front wheel bearings - all fine
Changed the wheels for some from another vehicle - no difference
Put the truck on a hoist and run it up to 55 - transfer case starts shaking - engage diff lock and the problem is almost gone.

Where to next??
Any clues?? It is a '98 300Tdi with 80000km.
:(
800,000 km......Hmmm

[abaddonxi]

Howdy all, Something to ponder.....

I have a harsh vibration under medium to hard acceleration at 55km/h (31MPH) and it comes in again at 100Km/h (62MPH). SO far we have tried this to no avail:

Remove rear prop shaft - problem stays
Remove front shaft - problem gone
Install brand new front shaft - no difference
Dissasemble and check centre diff - all just fine
Dissasemble front diff - all fine
Checked both CVs and front wheel bearings - all fine
Changed the wheels for some from another vehicle - no difference
Put the truck on a hoist and run it up to 55 - transfer case starts shaking - engage diff lock and the problem is almost gone.

Where to next??
Any clues?? It is a '98 300Tdi with 80000km.
:(


ding ding ding ding ding....

WE have a winner.

Flogged, siezed or otherwise not happy UJ, slip joints flogged out or the shaft has thrown a weight and is now out of balance.

Its rare but it could aslo be the output flange on the Tcase is out of true, slopping on its splines or the front bearing is on the way out.

have fun, dont keep driving it if the UJs aint happy, thrown front propshafts Aint exactly fun.

Two dud front prop shafts?

Cheers
Simon

[nzoliver]

Hi Graeme - Ran it without a brake drum to eliminate that!
Hi Simon - New shaft turned 'in phase' not out of 'phase'. I wonder if it was ballanced in phase and moving it to out of phase has shifted the ballance? UJs feel just fine on the old shaft.

[Graeme]

Gearbox mounts or less likely, engine mounts?

[agrojnr]

Panhard or Radius bushes completely shot or all bushes??????


Adam

[nzoliver]

Howdy
How would you tell?

[sich nich]

ive posted this on another thread, and i have no idea why the front prop shaft on discos and fenders have the uni yokes misaligned. they should be aligned flat, because in a mechanical sense, unis at both ends of a shaft that have the unis misaligned causes massive vibration. Yet this is how they all come from they factory.
I split mine at the spline, and reassembled it with the uni's aligned flat, and it drove heaps better, allowing higher top end speed, but i still had some vibration due to the flogged bearing inside the output flange.

[Slunnie]

It doesn't surprise me that it vibrates on the hoise due to the suspension and driveline geometry. Does it have any suspension lift at all?

[nzoliver]

Howdy!
It is a joe standard truck at the moment. In difflock the transfer case didn't leap about the same on the hoist but the vibration is still bad on the road. :( The general consensus is the front shaft output bearing. :mad:
The mechanics reckon it is good and has no rough spots. Maybe it is just best to change it.

[nzoliver]

:o
OK all! Here's the latest!

I MADE them change the front output bearing today. It has made an 80-90% difference!!!! BUT, the vibration is just still there at the same speed but only just. Now, i'm going to have the driveshaft ballanced tomorrow to see if that is the problem and if it ain't, well I'm not sure what to do next as this small problem could stuff another bearing in not too many miles and we end up back at square 1. :mad:


I'll keep y'all posted....

[nzoliver]

Hi all,
Well, it is better now. The new genuine donut had torn. On with a new one! I had a couple of weights put on the driveshafts (which were straight). The weights were VERY small tho. Right from the off it was smooth! Now, all I can sense is the 55km/h vibration but it is had to differentiate from engine vibration.
Now, could a bush in the rear end be rsponsible? Maybe the locator arm bush or similar?

Thanks all!:)

[nzoliver]

Howdy,
Hmm, well wheel ballance wed arvo if I can. Do y'all reckon the spigot bush should be changed with the donut? This is the bush inside the rear shaft that the spigot sticking out of the diff goes into? :eek: