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.
 

[Range Rover Blues]

That's a good one.  Obvioulsy the vibration at 100 is a harmonic of the main vibration at 55.

Now you've almost answered this yourself because the transfer box is vibrating, unless you engage diff-lock :-.  curiouos :-k

But I think the T-box is your problem.

3 questions, was the truck on it's axles whilst on the ramp or were the wheels "dangling" from the chassis? this will effect the front propshaft UJ angles badly and wear in the T-Box would be shown up worse than usual.

And is the truck lifted above standard, have you done any suspension work recently?

Finally, how quick did the problem appear?



I'd be looking for a collapsed bearing, a bent or loose shaft/flange or chipped teeth somewhere in the T-box.

[nzoliver]

Howdy!  :lol:
The axels were in dangle mode. The truck is bog standard as supension goes. I'm not sure how quick the proble appeared but it appears to be gettimg worse. It is less noticable when cold. Once the trans. box is warm then it is very evident. More so when it is hot.

Hmmm, its a doozy alright! :doh: We pulled the transfer box out and all looked good. Same with the centre diff. Took the plate on the bottom of the t/case off and no 'bits' or spare parts so no broken teeth etc. Oil was clean etc.

This is a damn nuicance!! :-k

[nzoliver]

Howdy again.. :roll:
The brand new front driveshaft that turned up was 'in phase' and probably ballanced as such. Would shifting to phase the 45deg that it is meant to be alter the ballance of the shaft? :-k If so that would make the new shft out of ballance and therefore useless. :doh:

[Range Rover Blues]

Err, hmm.

I tried for ages to get my head round why the UJs appeared to be out of phase, on early RRC it's about 30 degrees but by the 90s it was 45 degrees.

The best that I can understand it's because the T-Box and axle diffs are at different distances from the centreline of the truck, so that the UJs are in fact in phase, because of the unusual way the front prop is installed.

Anyhow, the difference it would make is minimal, a droning from the front end during coasting is the most obvious.  When I was trying to sort out oour lifted truck (before castor correction etc) I re-aligned the front prop so that the UJs were in line, because it was lifted 2" this helped.  I didn't experience any out-of-balance issues.

If the prop was built properly (no punn inteneded) then the balance issue will be minimal.


I've been trying to figure out why engaging difflock when it was on the ramp made any difference :-k, the first answer is that perhaps the 2 axles were running at different speeds and engaging difflock changes the speed of the front axle :?


If you can be bothered trying it again stick the truck up on axle stands rather than a lift so the weight is on the axles and they are in their normal position.

Meanwhile, check that none of you engine mounts have become damaged or gone soft, oil contamination can do this but check none are split either.

Do you off-road? could it be damage from striking something hard :-k

Does the gear you are in make much difference? obviously it effects the rate at which you accelerate but I have seen a combination of engine vibration and propshaft vibration that's worse in some gears than others.



You tried another set of wheels, so I take it you can't identify exactly what's vibrating.  How good are your shocks and do you feel the vibration through the steering?

Lastly for now, check the rubber coupling on the rear prop, both the doughnut and the spigot bush inside the back of the prop.

[nzoliver]

Hiya,
The gear doesn't seem to matter as yo can get it in low range as well at the same speed ( although to a lesser degree as the engine is reving its t*ts off at 55km/h!).   
Engine mounts seem good as do the gearbox ones. 
I don't have any droning but just virbation at what seems to be driveshaft speed.
The consenus on an American LR site is the front output shaft bearing. Might feel good but be knackered. The mechanics did run the bearing in their fingers and felt no rough spots.
The rear shaft has a new 'donut' so it's not that although we have not checked ballance of the rear shaft. In saying this, the problem went away when using the rear shaft only to test drive.  :roll:
Hmmm :-k

[Range Rover Blues]

Right, you've answered my next questions there already and I think the output shaft or bearings myself.  I'd do both though to be safe and whilst it's striped check the shaft for straighness.

As well as the rubber doughnut there is a small internal rubber bush, if you don't replace this the doughnut only lasts a short time, so worth checking that, Sometimes removing the front prop covers up probelms with the back prop as it's under more stress, but I don't think it's the case here.

 I have to agree that it's the output side of the T-box. It's just odd that difflock makes it go away, did you try engaging difflock when driving with both props on?

[nzoliver]

Howdy,
Yep. Same prob when in difflock 'on the road'.  :doh:
The old doughnut was ok just not genuine and a possible source of probelms but out it went anyway. There are no signs of belts to either shaft. A brand new shaft on the front gave us the same results.
Looks like the front output bearing!!

[Range Rover Blues]

Yes I'd have to agree, it's certainly the front end of the transfer box and IIRC the bearing isn't too hard to swap :-k

Let us know how you get on with it though ;)

[nzoliver]

HI,
Roger. Will do.

Thank you

[lurch_917]

might be a stupid question but have you checked the harmonic damper on the front axel its the dinner plate shaped part that somed times falls of and as its strange for this to happen it normaly over looked as a fault

[ben_haynes]

might be a stupid question but have you checked the harmonic damper on the front axel its the dinner plate shaped part that somed times falls of and as its strange for this to happen it normaly over looked as a fault

I never had any problems with mine when i took it off to fit my diff guard

[nzoliver]

Hiya,
All present and corect. 

I am now just about convinced it is the fron output bearing. But....this is Land Rover.....NEVER say never :shock:

[nzoliver]

OK all! Here's the latest!   8-[

I MADE them change the front output bearing today.  It has made an 80-90% difference!!!! :clap: 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.  :roll:


I'll keep y'all posted....   :?

[Range Rover Blues]

It's entirely possible that running out of balance due to the bearing has bent the front prop a tiny bit.  I had a rear diff bearing collapse and byt he time I'd stopped the truck the rear prop looked like a banana :-.

[nzoliver]

Hi all,

Today's information:
ANOTHER NEW donut - The old 1 had torn!
Ballanced both driveshafts - they were both out but by less than 1oz.
All this has made a difference - quite markedly.
Smooth now - EXCEPT fot the 55km/h point. I'm beginning to think now we have a bush issue, maybe the locator arm bush?

Thoughts???

[Range Rover Blues]

If the doughnut has torn that's a classic sign that the rubber spigot bush inside isn't doing it's job, but TBH I struggled to get my prop balanced and ended up having it rebalanced with the new doughnut on.

Also my LSE is as fussy as hell about wheel balancing and even some brands of tyres it doesn't like :-k at 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? :roll: This is the bush inside the rear shaft that the spigot sticking out of the diff goes into? Is there a part number for this? Or a picture?

[Range Rover Blues]

Can't help with ther picture but if you're buying the rubber doughnut then they should be able to get the bush.  Yes it needs swapping, if the doughnut has worn then bet your shirt the spigot has gone too.

Unlike the rotaflex couplings used by Ford and Triumph amongstthers the LR joint is not self-supporting.

[nzoliver]

"I also think that a lot of people dislike the rubber doughnut because they have had bad experiences with them, breaking up when nearly new and bad vibrations.  Ironically it's often down to the fact that the centre spigot get neglected when the doughnut is changed.  If you see chafing on the face of the doughnut then the spigot is goosed."

Hiya RRB! I pinched your reply (above) as it may pertain to my problem as well. I had a little chaffing on the front surface of the donut. I had the spigot measured when they were doing the shaft ballance and it was 15 thou out.  I'm picking this is causing the chaffing now after reading your reply. Also, have you a part number for the spigot bush as it doesnt show up in the LR service manual?

Thank you

Oliver :clap:

[Range Rover Blues]

It wouldn't be th eonly thing that doesn't show up on a LR manual

TBH it was propshaft technology in Rotherham who sorted mine out, so I never bought the bush on it's own.  I'll look but don't hold your breath.

[nzoliver]

Hi again,
Tues mornin here!!! Typing this around toast!!  :shock:
Would the spigot being 15thou out be a problem? Never had changed the bush. Is there a ball in there to centre the spiigot or does it just rely on the rubber insert? :roll:

[Range Rover Blues]

The spigot that comes out of the rear diff fits tightly inside a rubber sleeve or bush inside the back end of the prop.  15 though could be enough as you you are getting the chaffing on the doughnut itself, indicating it's running out of true.

[nzoliver]

 
Howdy!
Should there be an angle difference between the rear diff flange and the 3 spoke flange on the end of the drive shaft (causing the rotflex to be compressed at the 'top' and stretched at the 'bottom'? There isnt a huge difference but there is a difference and i'm picking the spigot inside the shaft will be causing the shaft to 'swing' a little as it sits further up the shaft than the 'centre' of the 'flex' joint.  :roll:Would I be correct in assuming this could cause a vibration? :-k

[Skibum346]

Howdy!
Should there be an angle difference between the rear diff flange and the 3 spoke flange on the end of the drive shaft (causing the rotflex to be compressed at the 'top' and stretched at the 'bottom'? There isnt a huge difference but there is a difference and i'm picking the spigot inside the shaft will be causing the shaft to 'swing' a little as it sits further up the shaft than the 'centre' of the 'flex' joint.  :roll:Would I be correct in assuming this could cause a vibration? :-k

Isn't that the job of the doughnut... in place of a UJ it allows the prop & flange to be at different angles...?    :-k

[Range Rover Blues]

No it should run fine at quite a noticeable angle, mine does, my car is lowered 1 inch but in high profile it's about 2 inches above standard and I get no problems.  In fact I think they dope ok with 2 inch lifts on coil sprung cars, where they run that height all the time.

If you still think it's the back prop then you best bet is a 200 series prop and change the input flange.

[nzoliver]

Hi,
Hmm, well if thats the case I dont know where to go next. Looks like we might have to pull the rear diff and see what's up.   :?  It i soooo specific in the speed area and under load too. Very light load it is hardly 'feelable' and it is worse when the driveline is cold. Is that another clue?? :roll:

[Range Rover Blues]

Well oil is thicker and rubber harder when cold :-k

Here's a thought, if it really is better when it's wrm, measure how warm each part is, say the diff, gearbox etc.  if it's a few degrees then I'd be sceptical but if say thegearbox is getting quite a bit warmer then perhaps it makes a difference.

I can see you chasing you tail on this one though, as you fix one part then another that you thought was ok is now the bit letting you down.l

I gave up trying to sort my steering kickback out and fitted stronger shocks for that very reason.

[nzoliver]

[!Expletive Deleted!]! :doh:
Should have read wot I typed. It is better when cold not worse. Worse when hot.  :roll:

I wonder if it isnt the top locator arm bush or shocks - either a binding one or they are too sloppy but the truck doesnt seem to bounce at all. In fact the opposite - this is a very harsh truck. The 2 lower sway arm bushes have been swapped for Nolathatne. Dunno why. The rest look ok and are origonal.  :-k
Chasing me tail is chasing me out of this truck and into the SII v8 i've got coming that I was going to sell.

[Range Rover Blues]

Ah, hard ride, bit of a clue.  Try slackening the shocker bushes half a turn, amongst other things you might be trying.  With a beam axle you have to let a small amount of vibration go unchecked.