Still vibrating under load...here are my findings

My TD5 90 is vibrating under load, here are my findins thus far and I would be very grateful for your comments.

My mechanic thinks it is the dual mass flywheel but I think he is wrong. I am inclined to think it is the front diff.

There is vibration under load only at road speeds above 45kmph. There is no vibration at speeds around 30kmph in 2nd gear at similar engine revs as around 45kmph in 3rd (I don´t have a rev counter so I´m guesstimating by sound). Am I correct in thinking that if it was the DMF then vibration would be dependent on engine speed and not road speed?

Next test:
I put the transfer box in neutral (to remain stationary) and then went thourgh all the gears at similar engine revs as on the road. And there were no vibrations whatsoever. If it was the DMF then it should vibrate? Also, if it is a problem with the gearbox then it would also vibrate?

Why I think it is the front diff.
I have recently broken my rear diff and replaced it. Perhaps front went at the same time? This was after I did some muddy offroading in the winter with freespinning the wheels. I don´t think it is the front prop as that has been replaced not long ago.

I´m just about to go and take off the front prop to see what happens. I´ll be back in an hour or so.

I really don´t want to keep throwing money at it... my mechanic would love to!

So i´ve taken the front prop off and it makes no difference. Probably isn´t the diff then. I also notice that it vibrates even when engine isn´t under load though not as much. Doesn´t vibrate when out of gear and coasting.

mikerajjers said:

So i´ve taken the front prop off and it makes no difference. Probably isn´t the diff then. I also notice that it vibrates even when engine isn´t under load though not as much. Doesn´t vibrate when out of gear and coasting.

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Where is the vibration being felt/noticed? You don't say. Through the steering, the engine/gearbox, in the tub?

When the DMF went on my last Mondeo it only vibrated on tick over. The engine shuddered a bit as it ticked over. ie not a balanced tick over. When in gear and driving I couldn't tell there was an issue.

Al2O3 said:

Where is the vibration being felt/noticed? You don't say. Through the steering, the engine/gearbox, in the tub?

When the DMF went on my last Mondeo it only vibrated on tick over. The engine shuddered a bit as it ticked over. ie not a balanced tick over. When in gear and driving I couldn't tell there was an issue.

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It is a general vibration throughout the whole car. It's not a steering wobble which would be caused by hubs, bushes or bearings.

mikerajjers said:

It is a general vibration throughout the whole car. It's not a steering wobble which would be caused by hubs, bushes or bearings.

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Clutch plate coming loose ...

Try it now with the front on and the rear prop off, just to eliminate the rear end.

I reckon it's clutch related, which would include flywheel ...

I will try the rear off tomorrow though its very unlikely as I've changed the rear prop twice and have s brand new diff

I changed my clutch and DMF on my TD5 last Christmas and in doing so discovered that the old DMF was loose and rattly. With the new one a lot of the funny groany whirry noises you used to get with the clutch down have gone. The release bearing and bush in the back of the flywheel which people usually blame for such things were in as-new condition but I changed them anyway. Not quite the same as vibration I know, but I'm just saying because the DMF can give you all sorts of odd symptoms as it's losing the will to live.

Right, I've taken the rear prop off and there are no vibrations! I noticed I had one different length prop bolt on the diff end. Could that cause enough weight difference to mess up the balance? I will get a new prop just in case as I remember mine came apart when I was fitting it.

Yes, a small weight could cause such vibration ... but much more likely that if you didn't put the prop back together in the exact splines it came apart from that might also cause it. If you're really unlucky, the imbalance this causes might be in harmony with the imbalance, however small, from the different bolt and be enough to cause your vibrations. Do a good check of the UJ's while off, grease them or replace them if you have any stickiness or play ..

Could the over size bolt be touching a yolk a bit at one point?

tottot said:

Could the over size bolt be touching a yolk a bit at one point?

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I will order new bolts. I had a bag of propshaft bolts but didn´t notice there were two different sizes.

mikerajjers said:

I will order new bolts. I had a bag of propshaft bolts but didn´t notice there were two different sizes.

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Longer bolts usually used on the handbrake side of the rear prop. Short ones everywhere else, unless you have a short prop and a spacer, but that's a modification for longer suspension, not a usual mod!

tottot said:

Could the over size bolt be touching a yolk a bit at one point?

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It's a possibility., but I doubt it, unless it's not a long prop bolt and nut and just something someone found about the same size to use 'cos he couldn't get the right bolt and nut.

Paul D said:

It's a possibility., but I doubt it, unless it's not a long prop bolt and nut and just something someone found about the same size to use 'cos he couldn't get the right bolt and nut.

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it was the long prop bolt from the packet. I´ve just ordered a new prop....OEM fron firstfour this time as the ones off ebay weren´t very good. The rubber is starting to perish on the front prop after less than 6 months and less than 1000km

I´m going away for nearly 2 weeks tomorrow so won´t get a chance to sort it before I get back

Just to update with my finding...fitted new prop today and problem solved. Drives nice now!

The prop had a red britpart sticker with a G suffix...is that 'genuine'? Bought it from firstfour4x4 and It felt much better built than the previous two eBay props.

Guess that the others were just not balanced right.