[mdss]

Good evening all.



Was doing quite a bit of spirited and side ways driving this week and today something strange happened.



After a little side ways action i noticed that as i geared down to second at high speed around 50mph there was a loud thumping coming from the rear sounding like the diff or something heaving banging under the car and also the gear stick was vibrating violently.



This only happens when the car is geared down at speed, it drives fine other than that engaging gears fine and no funny noises.



I am assuming that my diff mounts have finally given up the ghost, am i correct or have i bust something else.



Any advice is warmly received and thanks as always in advance for any help.

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[flash]

there is only 1, so maybe it went. it has been known to happen.

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[mdss]

Is that what it sounds like flash?? the thumping from the rear to me would indicate its the diff as its quite a violent banging and only happens when gearing down as i said. When i rev the car hard all the way to the redline in all gears ther is no problem what so ever.



Could it be rear axle carrier mounts or is that a daft question



thanks for the prompt reply, this is the problem with such a well balanced car i like driving it sideways and exiting corners becomes a pleasure!

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[flash]

well, there are all sorts of places that could cause violent banging and make is seem like it's in the rear. it may in fact be in the rear, but for example, when a clutch disk glazes, it can seem like it's in the rear.



clutch glazing is a common problem with this car, especially if you try to use the clutch to slow down, rather than the proper technique of blipping the throttle while in neutral, raising the rpms to the point where they will be AFTER the downshift, and then letting out the clutch. this is not a simple technique to master, and many people fail to do it, and consequently glaze their disk.



the bottom line is that you are going to have to get the car in the air to see if anything is amiss

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[tamathumper]

Could this also be a dual-mass flywheel failure?

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[flash]

possible.

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[mdss]

Hi

Guys quick update. today the banging from the rear has gone and i was not able to replicate, we got under the car the gearbox mount and all bushes on the rear were fine. Although when gearing down i.e from 3rd to 2nd for example the gear stick is still vibrating quite violently the higher the speed the worse the vibration.

We had to jack the car up as the ramp was occupied , but as i said nothing at the rear looked bad.My friend the tech said it could be engine mounts as the banging which occured the other day happened after a heavy session and his thought was maybe the engine mounts were worse when warm.



When accelerating hard in all gear there is no problem, to me it feels like a mount has gone but hey what do i know.



Do these cars suffer from engine mount failure? or may be torque tube problem but there are no noises or problems other than when gearing down.



Tomorrow the ramp will be free so i will have a good look at what ever you guys suggest.

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[flash]

you can tell if the mounts are bad. there is a measurement for them, but normally at idle the engine will vibrate the chassis.



i suspect either the DMF or the clutch disk, and more likely the latter.

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[mdss]

oh dear sounds expensive think the <acronym title='dual mass flywheel'>DMF</acronym> and clutch come in a kit together?



Should i change it immediately as i have no other problems when driving normally or can this cause further problems.



Thanks flash .....just when i was looking foward to fitting your short shift kit!

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[968TDG]

When my 968 is warm and I've been doing some spirited driving, I will have issues downshifting from third to second if I don't properly match the RPMs by blipping the throttle. It sounds like my issue is the glazing Flash is talking about. It is certainly worse once the car is really warmed up. It basically shakes the drivetrain violently, like the clutch only wants to be slipping or locked. I don't know if the problem you are talking about is a pulsing thumping like this, but thought I'd mention it. It's violent enough that sometimes I abort the downshift and try again with the RPMs properly matched. I can also notice this issue when I'm starting from stop on a steep incline when the car is warm. The problem is similar. The clutch is very jumpy, and makes it difficult to do anything precisely or slowly, like parallel parking on the steep city streets in San Fran was a pain...



Phil

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[mdss]

Phil exactly the same issue here.

I will still check the engine mounts tomorrow and report back but the hill starts when warm is the same issue here so we are both by the sounds of it in the same boat.

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[Ab54666]

[quote name='mdss' timestamp='1326139164' post='120218']

Phil exactly the same issue here.



[/quote]



Same here, a little blip on change down from 3rd to 2nd and it no longer happens. Just having a new clutch and lightweight flywheel fitted will see if it still happens after that...

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[mdss]

ab54666 keep us posted will be interested to hear what its like after its fitted

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[Ab54666]

[quote name='mdss' timestamp='1326143311' post='120222']

ab54666 keep us posted will be interested to hear what its like after its fitted

[/quote]



Will do, it'll be a few weeks as having quite a bit done (all new suspension as well).

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