Hi folks. My car is running really well, touch wood. I don't want to tempt fate too much here, but everything does exactly what it should and it just recently sailed through it' annual inspection. But, as my daily driver, I feel that I'm very much in tune with it and I've noticed recently, a sort of vibration throughout the whole car, very slight, evident in the steering wheel and in general, as an "all round" feeling. It isn't missing on any cylinders, idles perfectly, no light shows from the coils and I get the impression that it's something related to shocks/suspension/bushes/bearings/ propshaft, if that makes any sense.

Imagine the difference between running on a really smooth, flat tarmac surface, and then running on concrete, with the accompanying vibration. Today, I did an 8 hour round trip, mostly motorway at 75mph and the car sailed along, but still this niggle is noticeable. Sometimes it seems to lessen somewhat when I accelerate, or decelerate, or taking a long sweeping bend, left or right.

It's not a problem and no one else seems to notice it, but I do. Any thoughts on where to start looking? Likely culprits with regard to bushes? Rear shocks were replaced around Christmas, so that might be ruled out, but I wonder, would worn "A Frame" bushes cause the above? Anti roll bar bushes likewise?

I know this is all very vague but would appreciate any input or similar experiences. Thanks.

 

You could end up going through the entire suspension and steering looking for the cause!

Worn Rear A Frame bushes you've mentioned do cause transmitted vibration as do worn Vee mounts on the front crossmember. Worth a check on condition if neither have been replaced for a considerable time.

Graham

 

With my XJR I'm experiencing (what seems to be) the *exact* same sensation and under the same driving conditions. Like you I've 'tuned in' to the condition .....grrrr, I'd give anything to be able to ignore it....and nobody else seems to notice. In my case I describe it as more of a 'tingle' type of sensation through the car. Sometimes felt thru the body of the car, other times more thru the steering wheel....etc etc just as you describe.

I'm fairly sure it's related, somehow, to the driveshaft/prop shaft, but I can't confirm that. I've experimented with the left-right adjustment and that does vary the symptom but never eliminates it. I'm tempted to find a used driveshaft/prop shaft and install just as a guess.

A couple years ago I *did* have a pronounced vibration which was cured by replacing the center bearing and u-joints. But what I have now is much more subtle. I can't remember, darn it, when the problem began....but I'm sure it was after the above mentioned repairs.

I've visually inspected 'all things suspension' and found nothing. I really didn't expect to, to be honest. I also disconnectd the half-shafts and tested the movement/feel of those u-joints----smooth as can be.

I've also pondered the idea of a transmission fault of some sort .....perhaps a torque converter problem or such....but there's no easy or practical way to confirm that as far as I know.

I've used an electronic vibration analysis tool like this......

Kent Moore Eva Electronic Vibration Analyzer Tool J 38792 | eBay

....to no avail. It's a great tool but, in this case, the vibration is just too subtle for the tool to work.

I've resigned myself to living with the problem and *hoping* it will get much worse.....at which point it can be isolated.

Let's hope someone chimes in with a magic answer.

Cheers
DD

 

Would a fault with the vee mounts or rear a-frame bushes be apparent on simple visual inspection? Or is it a case where you can't really tell if they've gone bad until you take them out?

Cheers
DD

 

How hard is it to do u joints and bearings?

 

So I don't know if this is your problem or not, so it's more of just a question.

I'm an OTR truck driver. The service manual for most of the big rigs say to replace the crank shaft damper at 500,000 miles. Could it be, or should the damper be replaced at a certain mileage? With 291,000 miles on mine I was thinking about just doing it. Does anyone have any thoughts?

 

I've had 3 fail on 3 different vehicles. All gave sufficient warning of impending failure (but me being a bit slow on the uptake for the first two) - Excursion 7.3L decided to continuously toss the drive belt about a year after a short, high-pitched chirp developed on cold-start. S-Type 3.0L made the same noise on cold start for 6 - 12 mo. before it started shredding belts. By the time the X300 FEAD started making funny noises (not exactly like the other two, though) I had learned to mark the damper to determine if it was failing. Even so, first noise in April, and I changed it at the end of July - my daily driver averaging 70+ mi/day, and in this case it was still functional. With usage rates on your typical big-rig, plus the complications of a breakdown (it's no longer just you who needs a ride, but maybe 80K lbs of goods) a periodic change under planned maintenance is a good idea. For your car, maybe not so much.


Maybe put the car on a lift or jackstands and run it to isolate the suspension-induced vibes from the spinny-bits in the drivetrain? (just don't slip off - hitting the deck doing 50-60 mph from a standstill would likely break something expensive or at least be an E-Ticket ride!

 

Doug visual inspection can help but is not necessarily conclusive.

For the rear A-frame, check that the gap between the top of the bushing and the body and the bottom of the bushing and the arm are the same. If they are different it could indicate that the rubber internally has collapsed.

For the fee mounts, put the car on jacks and with the wheels removed you can get a good view of the condition of the rubber. Then take a pry bar and wedge it between the mount and the frame and see if you can see movement. While on stands you might also try using a jack under the subframe to push up slightly and see if there is any de-laminatation.

Best way of course is to remove them but you already knew that

 

Well, I took a good, hard look at the busings and vee mounts. I was really hoping to find something obvious and conclusive that I had simply overlooked before. It wouldn't be the first time

But, as luck would have it, they 'appear' to be in very good condition.

I'll have to do some mulling about replacing them. Not exactly a 15-minute job but I may end up taking the plunge..

Cheers
DD

 

As an alternative line of thought, I am also considering the possibility of fuel delivery issues, pointing at either the fuel pump, injectors, fuel filter and whatever else comes to mind. As stated, my car is starting and running fine, with no apparent loss of power, but the slight vibration/faltering might also be caused by the above. It's just that sense of the car not "humming along", which I suppose may well be expected of an 18 year old car.

I have a new fuel filter which I will fit soon and see if it helps. Although the one that's on it doesn't look very old and I have owned the car for almost two years, maybe a change won't do any harm.

 

Hi
Just an other part that will cause a viberation is the flexible jurid coupling at the propshaft end to diff flange part number CBC8996. These can get small unseen cracks and cause the prop shaft to rotate un even
Cheers Ray

 

I'll be ordering one!

Today I decided to give the coupling a good look....again.

It *looks* virtually pristine. Not even any of the tiny surface cracks that rubber parts even develop. I was about ready to 'call it good' when I decided to put a little pressure on the rubber with a screwdriver. Lo and behold a giant split appeared. Release the (very slight) pressure and the split completely disappears.

With any luck replacing it will solve my problem.

Cheers
DD

 

let us know how it works out? ... good luck and maybe some pics if you can...i might need to do the same....cheers

 

Changed the Jurid coupling and the vedict is.......

No change at all.

Drat.

Cheers
DD

 

Yes, it's disappointing when the fix doesn't work, but you can take comfort from the fact that it's one more improvement to your car, either way. It's one of those irritations that may just need working through and replacing certain items, but at least bushes and the like are fairly affordable. I intend to replace my coupling as a first step either way, so, we shall see.

Thanks for the update.

 

Doug,

I've gone through some battles with vibration just recently and believe it or not, it came down to the propshaft u-joints, even though I had replaced them! I'm working on a write up but don't be surprised if this is the issue, even though you have replaced yours.

 

I'm all ears, Allan

And I'm really dreading the prospect of changing the Vee mounts on speculation. That's a lot of work !


Cheers
DD

 

Well.....?

Are you trying to torment me or what ?

My interest in solving this problem....which waxes and wanes according to mood....is fairly high at the moment !

Cheers
DD

 

Sogood,

Like others I suspect your vibration is driveline-related, but a failing fuel pressure regulator could allow the pressure at the fuel rail to fluctuate and lead to uneven cylinder combustion, probably in a "wave" function as pressure builds and recedes and dependent on engine speed. If your FPR has never been changed, I would highly recommend putting in a new one as a matter of course. Too often Jag owners are not recognizing FPR problems until the diaphragm fails and fuel is sucked into the intake manifold, or some other issue occurs, like fuel pump failure or idle speed control system malfunction. I found an OE Bosch FPR for under $100, but other brands are available for as little as $40.

As far as your driveline goes, the two most common culprits of "hard to locate" vibration are the Jurid flexible coupling and the driveshaft/propshaft center/centre bearing (why can't our friends in the U.K. learn how to spell???). :-)

Cheers,

Don

 

Did the vibe present after your wife drove the car? Have you eliminated a bent wheel as the source? Sounds elementary, I know. But I had a Buick Century T-Type that developed a faint vibe only discernible at 60 mph+, then it became much more pronounced upon tire rotation. Think I may've had 'em rebalanced more than once before the tech identified a bent wheel. Previously, I'd driven alongside it in a separate car and observed both sides, front & rear at highway speed and there was no wobble nor other problem visually evident. Replaced the suspect wheel and all was well.


Since we have full-size spares in these, maybe put the spare on and move it through each of the four positions to see if any effect?