mike_hammond

Recently I've noticed a vibration when accelerating moderately hard and its also present and more noticable from around 100 upwards. At normal cruising speeds of between 60 to 80 its smooth as smooth.

I feel it through the whole car through the seat of my pants but only on smooth road surfaces (highway for you guys ), when I'm on rougher back roads its not noticable over the normal feel of our UK road surfaces. There is no associated noise like a bearing rumble, I've checked my front wheel bearing adjustment, tyre pressures, drive shafts, ball joints and bushings and nothing seems to have any noticible wear or play, the DMF was replaced last year so I'm a bit stuck at what else to look at ? Would a poor alignment do it as I've yet to get it checked after replacing the A-Arms and castor blocks ?


Cheers

Mike

BruceWard

Mike, I do not have knowledge in this area, but I think that having it aligned is a good place to start. When were the wheels balanced last?

RajDatta

I would 2nd the high speed alignment. After that the next culprit would be the torque tube.
Raj

flash968

here's one for the "odd stuff" book - ron just had this problem - turned out that his wheels were mounted wrong - the lug lock was not opposite the valve stem

mike_hammond

No lug locks on CS's another weight saving/money saving pearl of wisdom by Dr Porsche I wish it was that simple.

New front tyres and a balance tomorrow, I'll get the alignments checked Thursday when I'm passing by Ninemeister's

BruceWard

On some of my hubs the red paint is still on the lugs on others it is different. I use the lock in any position and have not noticed any ill effect up to 140.

flash968

yeah - this was a weird one - the theory going was that the red dot was to line up the valve stem and then the lug lock countered that weight - i weighed the lugs and it made sense - found out completely by accident about the high speed vibration

i tend to think that what is going on is a balance issue, and it sounds like you will have that resolved tomorrow - check your wheels for roundness too when you are balancing them - a slight tweek and you could get what you are talking about

here's hoping you don't have to get into the torque tube and such

PorscheG96

The red dot is opposite of the valve stem, that way you thread the locking lug nut onto the red dot and it is also opposite of the valve stem.

flash968

yup - that's what the manual says

i am hoping he has a balance issue - the thing that scares me is the "acceleration" issue - balance should not affect throttle positions - that is something you typically see in a driveshaft

mike_hammond

OK, got the new 225/45/17 Goodyear F1s fitted on the front today....WOW what a difference a pair of tyres make (especially the right size !!!) I've had F1's on the rear for about 2 months but have been waiting to finish off the 205/50/17 P7000 Pirellis on the front and now I have its transformed the feel, so pointy, so solid mmmmmmmmmmmmmm love it.

Anyway back to the point, vibrations are now all but gone since the new tyres and balance, looks like the front passenger tyre had been clipped at some stage as there was a chunk of rubber missing from the tread on the inside exposing the cord !! lucky that didn't let go !!

The only vibe I get is a very slight resonance at 100+, but it is Very slight so I'll live with it for now and see how things develop. It certainly feels like a driveshaft given that its dependant on road speed rather than engine & hence torque tube speed. At 140,000 I suppose it to be expected, especially now I've done all the bushes etc up front the rear is bound to start showing up more.

I'm still going in to get the geometry checked on Thursday, since changing the wishbones and castor blocks could have put it out, but so far she feels much much better.

Cheers for the pointers gents

Mike

flash968

now there is a clue, but you got it backwards, unless you are calling the axle shafts driveshafts - in which case, ignore the following

if it's dependent on road speed, then it's something to do with wheels or their associated components (barring an odd thing in the gearbox) - if it was engine or driveshaft related (the driveshaft being located in the center of the torque tube and spinning at the same speed as the engine), it would happen at a specific rpm, regardless of what gear, and therefore regardless of road speed

make sure it isn't in the gearbox - find the rpm in top gear that it occurs - then match that rpm in all other gears and see if you have the vibration - then double check that it doesn't do it sitting still with both the clutch pedal up and down while in nuetral

BruceWard

Mike, glad to hear you have some improvement.

Have you checked the boots on the CV / axle / drive shafts (thingies between transaxle and rear wheels). One of mine was cracked so I repacked the bearings and replaced boot. I believe that repacking them should be a maintenance item. I plan to do the other three someday.

mike_hammond

Flash just to clarify we call the "axle shafts" drive shafts over here ( just to confuse you guys ) as you'll have now gathered I did mean axle shafts and the very minor vibe does seem to be road speed related so I don't think its the Torque tube, more and more likely one of the rear wheels out of balance to be honest, why didn't I get them checked today ??? DOH !

In answer to your question Bruce, yep checked the CVs at the weekend and all was OK, I have actually got planned a regreasing session with some nice fresh Redline CV2 in the very near future, I think its every 50K miles they should be done so its about due.

all good fun huh !

Cheers

Mike

flash968

i thought that might be the case - i should also have added "propeller shaft" for driveshaft too

yeah, you'll probably correct the last bit when you balance the rears

good deal - glad it's working out

mike_hammond

You mean the Prop shaft its almost a whole other language how did English get changed into American English anyhow ? and why do you guys spell colour without a U ? and why do you say tomato when I say toma"r"to :lol:

Mike