[Littelwill]

Ok so this is being asked on behalf of a friend of mine who has got a real bad vibration in the cabin of his p38 diesel auto it seems to be getting no worse but is really annoying.

It only does it at Idle and when he is slowing to stop at lights or a junction but disappears completely when the revs are increased or he pulls away. Hes searched and searched and it seems that others have had the same issue but never seem to get a final answer as to what it was or how they fixed it.

So I'm putting this thread together for him to try and finally find out
A) what causes this "Dreaded vibration" and
B) how it can be fixed.

So i need your help please have you had/got this? what are your thoughts?


Thanks

 

[Fergie46]

Check exhaust routing/tired mounts or engine and transmission mounts,too.

 

[Littelwill]

Engine and gear box mounts are all new... He has taken the exhaust system off and still gets it. It only happens when the vehicle is warmed up. If you lay under it whilst its running it sounds like it comes from the transfer box?

 

[stuu]

It sounds like an exhaust hitting the body like on downshift on a manual car. Mine started making the noise then next day father in law showed me it sounded like an exhaust vibrating on a plastic bumper upto 1200 rpm then it made a slight noise at 2kish then foot down to build up speed from 30 to 60 and then the big bang theory came to life

 

[stuu]

It took a total of no more then 16miles from noise starting to bang. No signs before noise started just after a start up. Its very sudden no warning. Only real suggestion would be to drop the drain bung on bellhousing and look as its spinning and see that the flex plate isnt like a buckled bike wheel when its spinning and that its not the bodies of the t/c hitting each other. If it is and you have to remove box pm me iv got pics ect from when i did mine

 

[Littelwill]

I'll get him to have a look at it theough the inspection plate tomorrow. I think he has had a look but not with it running. Might be a stupid question but what should we be looking for to make sure it's all normal?

 

[stuu]

Just look thats when its turning its turning true. Any movement at all off center or out of true on the plate the outer part of the tc can be seen turning with the plate if visable make sure it isnt moving in or out or up and down. I didnt see plate before it went bang just afterwards when she was together and running again. Any out of line in that bellhousing is damage time everything has to be 100% even fitting the box back up. Not like a manual you can sort of line it up and wiggle into place it has to be pushed back to block dead square and only once and straigh and true the whole time onto dowels. And also the plate canot push on the tc it sits flush to it then bolts take care of the rest

 

[Datatek]

Check the crank pulley torsional vibration damper.

 

[Littelwill]

Ok thank you. he's going to look today. What are your thoughts on it only happening when it's warmed up? Surely it's all spinning all the time so why does it being warm make a difference?

 

[Datatek]

Ok thank you. he's going to look today. What are your thoughts on it only happening when it's warmed up? Surely it's all spinning all the time so why does it being warm make a difference?

It's been covered a few times before, idle revs drop when warmed up which shows it up more. A crank does not actually spin smoothly, it turn in a series of very small jerks, hard to detect without specialised kit, the damper smooths these movements which appear as vibration.

 

[stuu]

Mine had only covered a mile most downhill just before it went so wasn't really warm at all. Unfortunately i was passanger in the back when it happened no invetigation before it went bang. Its only a thin stainless triange plate really dosent look upto the job