Vibration, for serious discussion only

[Mudlark]

Well with due reverence ....

I drove nearly 1500 miles convinced i had a failing UJ on the prop only to have a wheel wheel bearing collapse on Korcula.

That had some good vibrations going on at 70-90kph only and disappeared at 100kph so i would also pay some attention to my bearings and hubs; check to see if you have any play in them ?

[axeman]

on the subject of gear box and diff mounts, 20 years old against new. the old ones are rock hard and have compressed about 10mm, the new onwes are much softer, they cost about £12+vat from tps, 6 for the diff and 4 for the front of the gear box.




neil

[HarryMann]

Well with due reverence ....

[PC52]

Prop is GKN super dooper slider job, as its off at the mo that isn't the problem.
So the done list: Wheels and tyres removed & replaced with BFG ATs
Front and rear w/bearings checked, replaced n/s rear, o/s rear very slight , don't think it's enough to cause the vibes.
All cvjs checked, double checked and replaced the ones that needed
Swapped all drive shafts over etc as per Neil's suggestion
G/box mounts checked and swapped for known good ones,
E/mounts checked all good.
Taken for a drive with engine lid off absolutely nothing evident from the top whilst inspecting
Placed a bit of cushioning by the charge cooler 'just incase'
Checked snorkel was okay
Nothing evident on g/stick or clutch pedal

So in comparison to Clive's and ours yes both diesel but then everything else is different setup and power band, although this is a guess at rpm (not adjusted rev counter yet) vibe starting around 2000 mark and finishing around 2800 mark, more power = louder / aggresive vibe.
The vibe is 'tickly' under foot, noise somewhat throaty but similiar to a washer rattling in a can.

[syncropaddy]

Maybe its a German policeman checking you vehicle details before you are issued with a speeding ticket and he is tapping on the floor trying to get out from underneath

[HarryMann]

NB. SPad mate, Re: Vibration, for serious discussion only

vibe starting around 2000 mark and finishing around 2800 mark, more power = louder / aggresive vibe.

Definitely, more power = louder / aggresive vibe., same as mine

Pete, are you using the best Morrison's or Tesco's fuel, I found that BP, Esso and Shell setup some dreadful shock-waves through the bodywork

The mirror becomes a total blurr at 2200 and full boot, Ughhh!

Drain her out into 25 litre drums, put them to one side for me when I come up there, and brim it with Sainsbury's best.. see what happens

[PC52]

NB. SPad mate, Re: Vibration, for serious discussion only

vibe starting around 2000 mark and finishing around 2800 mark, more power = louder / aggresive vibe.

Definitely, more power = louder / aggresive vibe., same as mine

Pete, are you using the best Morrison's or Tesco's fuel, I found that BP, Esso and Shell setup some dreadful shock-waves through the bodywork

The mirror becomes a total blurr at 2200 and full boot, Ughhh!

Drain her out into 25 litre drums, put them to one side for me when I come up there, and brim it with Sainsbury's best.. see what happens

Clive!!!!
What are we talking about here fueling issues? Thought we'ld done this one. Back of the lorry fuel, always works best.

[PC52]

Maybe its a German policeman checking you vehicle details before you are issued with a speeding ticket and he is tapping on the floor trying to get out from underneath

Nah, dumped him, he caught vlux doing 75mph on Saturday night 1 1/2 hours away from Stadtoldendorf on a slipping clutch.

[v-lux]

Tee hee.....

[Russel]

I had a very similar problem with a syncro camper i bought about 7 years ago. With or without prop same vibration.
I bought the van for the syncro drive train. So fitted a 2wd gearbox but vibe was still there. i then removed the front diff and fitted some stuffed outer cv casings
to hold the wheel bearings together and hey presto Vibe gone. Never found out exactly wot is was but it was up front. Either diff or driveshafts.
Russel

[v-lux]

Im still wondering about the front diff output flanges.

Have you given a wiggle to check for excessive play?

[HarryMann]

It's possible for the VC to develop play on it's splines and that's a heavy bit of mass (Oops! a bit tautological that) jumping around.

Russel will remember a certain VC that had stripped its splines almost completely.. that shock the thing all the way to Coney Farm, but a more fundamental sort of shake, like a Tuba is to a French horn, when compared to what I have now (if you don't push that r/h pedal at low/mid-range wouldn't even know its there). It was alwasy there, slowing down through 40 and accelerating too (well, call it gaining speed in those days)
That was no doubt a result of no oil in the front diff for a few years, normal BBC servicing I presumed!

[HarryMann]

M Ajovalasit1, J Giacomin1

The University of Sheffield Department of Mechanical Engineering Sheffield, UK

Abstract

The variations in diesel engine idle vibration caused by fuels of different composition and their contributions to the variations in steering wheel vibrations were assessed.
The time-varying covariance method (TV-AutoCov) and time-frequency continuous wavelet transform (CWT) techniques were used to obtain the cyclic and instantaneous characteristics of the vibration data acquired from two turbocharged four-cylinder, four-stroke diesel engine vehicles at idle under 12 diffierent fuel conditions. The analysis revealed that TV-AutoCov analysis was the most effective for detecting changes in cycle-to-cycle combustion energy (22.61 per cent), whereas changes in the instantaneous values of the combustion peaks were best measured using the CWT method (2.47 per cent). On the other hand, both methods showed that diesel idle vibration was more affected by amplitude modulation (12.54 per cent) than frequency modulation (4.46 per cent). The results of this work suggest the use of amplitude modulated signals for studying the human subjective response to diesel idle vibration at the steering wheel in passenger cars.

pdf format

First page preview

[PC52]

Im still wondering about the front diff output flanges.

Have you given a wiggle to check for excessive play?

They have had a wiggle - as have alot of things so they will be on the list for a second wiggle

[syncropaddy]

Has the VC thrown a balance weight?