Pagnobito

Go to Post #52 for update..

I've searched and read lots of threads but they either do not match the symptoms or if similar have suggestions but then finish with no resolution or feedback unfortunately.

I like my 95,000km 928 Auto but I don't like to drive it as it makes me feel sick.

It's always had the problem, better after the mounts were replaced with Volvo type. There might be two different problems as there is a vibration that comes in around 80mph and gets worse, speed not engine related.

You can't feel the other problem until after driving a few miles it makes your head feel fuzzy, your vocal chords feel like you have been submitted to sub harmonic frequencies and you exit the car feeling like you've been on one of those simulator rides with a hint of travel sickness.

I've read enough to check rotational mass behind the TC to rear wheels. different wheels that work fine on another car didn't change it. The drive shafts appear to be good. It had a bad bearing in the TC housing when I bought it which could have been caused by an imbalance of the TC but would expect to feel that at engine not road speed as it's always spinning (couldn't feel it, but hear the bearing whine). The TT and bearings check out OK.

I've done a refresh of the intake including knock sensors, replaced various engine HT items and replaced the leaking vacuum reservoir which led to an improvement in engine manners, pickup and acceleration along with improved gearbox characteristics. MAF re-calibrated via JDS. The sickness inducing vibration is intangible, I don't know if I will ever find that one.

I could throw money at it replacing drive shafts, brake rotors, hubs, bearings and so on. The UK MOT passed fine with an advisory on one of the front lower ball joints has a bit of movement so that will be done but I doubt that would be a cause here.

It's parked and I like to look at the car, drive it not.

Schocki

Since you are talking about vibration: what is the status on your rims? Are they straight and have been checked? Tires in good shape overall?

Pagnobito

Brand new tyres on checked and balanced Speedlines, was also the same on previous tyres, replaced out of age and to see if it made a difference. I also ran it on some D90s with new tyres off my '79 which didn't make a difference. They went with the car end of last year and I put this one away to think about what I am going to do with it after trying to find the issue(s) for 18 months previous.

I carried out the engine work and TB etc over the winter.

I read on one thread "does it have spacers" as a question to another car with issues, I think Bill's car. His doesn't mine does and I hadn't thought about that before, it's an S4 in GTS clothing.

69gaugeman

Wheel bearings can be the source of low frequency drone but at 95k I wouldn't think it was an issue. Also CV joints can do that too. Check your front wheel bearings as well. All those items are speed related and can cause that type of vibration.

FredR

Am I correct to understand you have the one symptom [the speed vibration] and it is this phenomena that also causes the nausea you refer or is that some other phenomena?

For purposes of completeness has anybody else driven the car and experienced the same sensation? Vibrations can be annoying and in the extreme downright uncomfortable but what you describe I have not come across previously. I have read of people who are affected by light reflections coming off the dash panel or wherever making them feel queezy.

Assuming your torque tube and half shafts are OK then the vibration sounds like a wheel or more likely a tyre fault problem. If so a good quality tyre shop should be able to pick up the problem on a Hunter wheel balancer or similar. Have you checked the boots on the half shafts? Not actually sure how to check the half shafts but they should also be eliminated as the cause of any vibration.

The only thing I can vaguely speculate for the nausea would be if your dampers are shot and at some particular road speed the car starts to pogo a bit, nothing too dramatic but something that specifically affects you but if it was I would expect you could feel this happening. On my 90S4 I felt the car was unsettled going into bends, probably because of the transition from the softer spring rate to the firmer one- that problem disappeared when I went to Eibach springs and Bilstein gas dampers.

Best thing you can do [if you can stand the journey] is to pop over to see Paul Anderson in Stroud and get his take on the problem if the tyre shop cannot diagnose anything for you. That or maybe Adrian up in Cambridge if he has some time/inclination to advise.

Rgds

Fred

Pagnobito

Thanks Fred,

I've owned 928s for a few years now, this is the 4th and one I was planning to keep as cosmetically at least it's in very good condition with leather everywhere inside which is added evidence it has only done 95,000Km or around 57,000 miles. I know Adrian and a few others in the 928 UK community and I am planning to visit Paul in a few weeks for the PSD system. He has looked at it before and could not conclude the issue in the limited time it was with him.

I don't know if there are two different problems with vibration, there's no noise with it by the way and I've had a bad wheel bearing on a previous S4 so I know what that's like. It could be that the low level vibration is amplified as the car increases in speed and becomes tangible at higher speeds and hopefully if I can fix the one I can feel then it might cure the other that makes me feel sick.

When I replaced the bearings in the nose of the gearbox I had obviously dropped the rear frame and separated the torque tube at that time and checked it all.

I've also had cars with sad looking and bouncing suspension and although this one is aged doesn't give a floating ride or nose dive as one would expect with tired struts. I do however have replacements which will be fitted at some point. I should add that if you look at the picture the ride height is pretty good if a slight bit low at the back.

Chalkboss

Have you checked that the transmission mounts have the proper spacing from the crossmember... A few mm as specified in the manual. After pulling my transmission I overlooked this and had a vibration. After adjustment vibration went away.

Pagnobito

Yes, I checked that and the problem didn't change after the gearbox was refitted and checked again after the bearing swap. Also used a new front and rear pinch bolt. Have since fitted a Ritech clamp on the flex coupling but that's just for information, the end float was fine so just a preventative measure.

the flyin' scotsman

Are you referring to the Torque Convertor bearings? How was the TT checked?

how are the TT clamps front and rear?

I would start at the wheels and tyres then go from there. One step at a time.

Pagnobito

As in my first post, the bearings in the nose or TC housing, there are two, the inner one was making a noise.
Clamps and splines are good, new bolts and Ritech clamp at the front, that didn't nor did I expect it to make a difference as it is just there to prevent clamp migration.
I am aware of bearing migration so checked the TT by listening to it as I turned the shaft, position of the visible bearings and deformity with the same gauge I used to measure the end float. It ran true and quiet.

You say go from there, wheels are good, what's next?

Cheburator

Diff bearings...

the flyin' scotsman

thx for the clarification.

Given you have ruled out the wheels, tyres, TT, clamps etc it would be interesting to try and eliminate the engine. I seem to remember someone disconnecting the flex plate then running the engine to troubleshoot if the vibes are coming from there?

Search may reveal who but Im thinking Bill Ball or Mr Merlin.

Pagnobito

Indeed, problem is I don't actually feel any vibration until over the speed limit, the one I can't feel is the one that makes me feel sick at any speed which is why I say intangible. I don't fancy running the engine at cruising RPM when stationary for 10 minutes to see if it affects me but I have thought about taking it to a rolling road where it might be easier to visually check while running at road speed. Idling is smooth with only the very slightest feeling the engine is running other than the noise of course.

I had a thought when driving my daily car which has a switchable exhaust, maybe it's the resonance of that causing the problem in my 928, (not the high speed vibration). It's a standard Cat equipped exhaust but I have no idea how I would test for that without swapping to a completely different maybe more open flowing or better silenced one?

I may still try disconnecting the engine from the TT to see what difference it makes.

Pagnobito

Thanks Alex but I would expect them to make a noise before getting bad enough to cause vibration. I'm pretty sure they are good anyway as there wasn't any lateral movement at all in the stubs the drive shafts attach to as I removed them to check for wear when the gearbox was off and when I changed the diff oil.

jetson8859

In reading original post you mentioned two different issues one was a vibration starting at 80mph and getting worse with speed. The other you mention:

"You can't feel the other problem until after driving a few miles it makes your head feel fuzzy, your vocal chords feel like you have been submitted to sub harmonic frequencies and you exit the car feeling like you've been on one of those simulator rides with a hint of travel sickness."

My comment is this: is it vibration related or other? you say you can't feel it but it makes your head fuzzy, affects vocal chords and hint of travel sickness. Have you checked for exhaust leak into cabin, I have similar problem with a car and it had a leak on top of exhaust pipe at CATS connection near gearshift (5 speed Mustang) and I would get headaches, sick feeling everything I drove it. You really couldn't hear the exhaust leak and only by chance was it found. However, when it was fixed headaches and sick feeling went away. Just my thoughts.... you have a beautiful car so I hope it is sorted out soon!