Drivetrain massive Vibration

[F355GTS]

Further to a previous posting asking about vibrations on Lefthand tunrs under drive I've done a bit more investigation.

 

Having lifted the rear of the car off the ground tonight, I started it, all appears fine untill you put it in gear and engage the clutch, the car tries to virtually shake itself apart with a thumping and clattering noise, dip the clutch and the problem goes away. if you increase the revs the shaking etc smooths out although there is still a substantial vibration

 

At this stage I can't easily tell if it's Gearbox, Propshaft or Diff although there appears to be no noticable movement in the Propshaft (as in running out of true)

 

The problems all follow on from a rear end rebuild after an upper diff mount snapped together with one lower bolt, At the time all diff mounts, A frame bushes etc etc were renewed, even greased my nipples!

 

I've checked the Diff alignment to Chassis and it's spot on, all forward gears create the same situation in terms of vibration

 

 

Any ideas?

 

 

thanks

 

Mark

[thinfourth]

since the diff mounts snapped and you are getting vibs i would say it is prop shaft related as that might of accelerated failure of mounts

 

Also try car off ground without wheels incase you got buckled wheel

 

Blatting round aberdeen wondering wether to buy a jumper or heater

 

Edited by - thinfourth on 28 Apr 2004 23:16:00

[Red SLR]

Do you have access to a prop shaft to try?

 

Also are the half shafts ok?

 

Was your car not at the handling day the other....day?

 

I saw your car at Arch a few weeks ago 😬

 

 

[simonstevens]

get under the car, grab the prop as close to the diff flange as you can gat your hands on it and try and push it up and down, if it has more than a thou or two in play then pinion bearings are shot! these get worse under load! otherwise, could be the diff internals, didnt see your previous reply, is it a plated diff or viscous?

 

but hey, what do i know?

[simonstevens]

wheel nuts!

 

but hey, what do i know?

[Sideways Mike]

Hi

 

I had vibration problems with the rear of my car, mine had a vibration which increased as the speed did. This turned out to be a u/s driveshaft. I would doubt it is the diff because they usually go bang because the tolereances are so tight there is no room for play. I borrowed a friends car and removed his driveshaft assembly and installed it into my car this takes about half an hour per side, its cheap and does give positive answer (although in my case and expensive one).

 

Mike

[xflow7]

I'm not familiar with the De Dions, but on the live axles it is possible to get the propshaft and diff flanges slightly offset so that they do not seat together properly. Never done it without catching it first, but I imagine it could cause an unholy vibration.

[EFA]

Mark,

 

Humour this if you like, but check the alternator body is not cracked and that the alternator mountings are tight.

 

Fat Arn

 

Slay the K.

 

[Sheds Moderator]

On an old Spit I had this and tried without wheels, then without drums, etc until I'd identified it. I don't know if you can split the driveshafts off the diff, if so then you could run the car without and see what happened. The propshaft is the obvious most likely cause as you know but it's not easy to test without removing EVERYTHING. Prop vibration usually takes the form of a resonant vibration through the car and will as you describe reduce at certain speeds. The fact that it follows a diff mount problem suggests the prop Ujs as above.

[Rob Walker]

Flywheel bolts. I had two snap and the vibration was terrible.

[F355GTS]

Thanks guys, I'll work through the suggestions later and report back!

 

 

 

Mark

[F355GTS]

Update to answer some specific points

 

Thinforth, yes I thought this last night although there was was no noticable vibration before the diff mount failure

 

Simon (Scott), yes my Daughter did the handling day in it, it was o nthe way home i noticed the vibration when turning left, the halfshafts appear fine (o/s one looks new), haven't got a spare prop, are they the same on all cars?

 

Simon (Stevens) LSD is AP Suretrac I believe which makes it a viscous type I think? going to try it tonight without the wheels but my nuts are tight will check for play in the prop/ front diff bearing

 

Sideways/ Battered, I did take the driveshafts off last night and they appear fine, will run it tonight without them as Battered has suggested

 

Xflow, I will check, by eye it appears to be running true but I don't think it's possible to mount it off centre

 

Arnie, Alternator is new after the old one fell off at Combe (1st run after rebuild) I am wondering if there is some connection as the vibration may have caused the top alternator mount to fall out of the block

 

Rob, probably the last thing to check due to amount of dismantling!

 

 

Is there any reason why I can't run the car engine/ box without the prop just to eliminate them? (I appreciate that it may be messy with oil coming from the rear of box)

 

 

Anybody got a known, good propshaft I can borow to prove either way (Car is a '92 VX 2.0, 5 Speed dedion_

 

 

 

ta

 

Mark

[Red SLR]

haven't got a spare prop, are they the same on all cars?

 

They are different lengths, I dont think one off a K will fit your car and vice versa.

 

 

 

 

[deanteam]

Perhaps a long shot, is the bearing in the tail housing of the gearbox ok? We have had one on a 4-speed go with similar vibrations.

[F355GTS]

Dean

 

Could be suspect, at the same time the diff mount broke at Brands the plug opposte the speedo drive fell out!

 

Mark

[Graham Perry]

Agree with Deanteam. input or output shaft bearing failures can also give similar effects (been there and bought a whole box of T shirts) ☹️

[F355GTS]

Ok

 

An update so far, same problem with wheels and driveshafts removed, No obvious damage to Diff and no noticable play in front bearing, propshaft U/J's appear good with no play at all although one in one direction has a slight notchiness (is that a word!)

 

Shaft at rear of gearbox can be moved probably 1mm in any direction, is this normal?

 

There is evidence that when the Diff mount failed the flange of the prop hit the Chassis bending one of the small tubular rails slightly, I though maybe the propshaft was bent but then the problem was not evident immediately after rebuild.

 

Tempted to send Diff off to R&R to see if they can find anything

 

 

Anybody know where I can get a propshaft tested for straightness/ balance?

 

Mark

[Paul Gibb]

Mark,

I have a spare propshaft off a '95 dedion Vx in the garage which you are welcome to have FOC - it was routinely changed this winter (after reading Anthony's posts about propshaft failure last year) & AFAIK it is fine. Email me if you are interested.

Paul

 

L7 FUN

[Paul Gibb]

Mark,

I have a spare propshaft off a '95 dedion Vx in the garage which you are welcome to have FOC - it was routinely changed this winter (after reading Anthony's posts about propshaft failure last year) & AFAIK it is fine. Email me if you are interested.

Paul

 

L7 FUN

[F355GTS]

Paul

 

YHM

 

Mark

[Paul Ranson]

I reckon it's the bearing in the front of the diff housing.

 

It's at the centre of the previous event.

An out of true prop would probably vibrate before it would clank.

It seems unlikely that an event at the diff end of the prop shaft would cause a problem in the gearbox.

 

OTOH I'd have thought the sound would be locatable to that area?

 

I've had broken teeth in a straight cut box, no noise until a little load is put on, and then it clanks horribly. I don't think this is your problem!

 

Paul

[Sheds Moderator]

I agree with paul that out of true props vibrate not clank. I've had this and it's a bit like wheel balancing except that it runs right through the car at certain speeds. At low prop speeds obviously it's no problem, it just comes in and out as you hit resonant frequencies and various harmonics thereof. I'm sure you know this already, so sorry if this is granny and eggs.

[Michael_E]

Mark: this maybe a silly sugestion, but have you checked your engine mounts recently?

 

I only say this as I've seen several cars come into the workshop with vibration issues that appear to be rear end related but are caused by the engine being loose.

 

Just a thought.

 

Michael

 

C7 MLE

here

Spouting bollox so that you don't have to, since 1969

[AndyA]

Very interested in the content! Have a similar problem, when cold everything is fine, however when hot (post race) the whole back end seems to judder and clank, etc. At Brands there was a red flag and so for the restart the car was 'hot' and it sat there and juddered as i tried to start and evryone went past me

 

But during driving/racing there is no noise/juddering , has been suggested that there may be 'contamination' on the clutch plate.

[ECR]

If you can move the prop as it exits the gearbox 1mm in any direction (which is what I understand from your post), the rear plain bearing in your gearbox remote extension is very worn....

 

If the prop is able to move then it is able to run eccentricaly (which would give vibration....)

 

Edited by - ECR on 30 Apr 2004 13:24:08