Vibration when Decelerating

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awillemsen

Active Member
Posts
210
Location
Llandrindod Wells, Powys
My 2000 4.6 P38 has developed a vibration and (as a relative novice) I don't where to start looking, so some help would be greatly appreciated.

It happens when decelerating above an indicated 70mph. So, for example, if I go up to 70 and then take my foot off - nothing. But, if I go up to 75 and do the same then the vibration starts until I get down to 70 when it disappears.

Vibration can be felt through the handbrake, gear stick, and especially through my feet :) There's also a low growling sound - which if you weren't listening for it you probably wouldn't notice.

Tyres are in good nick and were new about 18 months ago (Scorpion STs all round). Car has been serviced regularly, but not sure if transmission or gearbox fluids have been changed recently. MoT was a couple of months ago at a reputable place - no advisories. Note that the vibration appeared before the MoT and has very slowly been getting worse.

The question is - where do I start? Or is it best to just book it in??
 
Does it do it if you go to 75 take your foot of and put it in neutral?

Yep - exactly the same in N, D or 3.

Today, vibration is less (hardly noticeable) but sound is louder (noticeable if radio isn't on).

Decelerating from 80 gives constant sound until 72, then it goes quieter until it disappears at 70.
 
I've just checked the MoT history online (thanks to another post) and discovered that the MoT just over a year ago (when I bought the car) had an advisory: "Offside Front Ball joint has slight play". I haven't fixed this, and I can bet my last penny that the dealer who sold the car to me didn't either. So, would this cause the noise and vibration?
 
It could but it sounds like it is coming through the body as opposed to the steering wheel might be worth checking the shock bushes at the top if worn could be allowing the wheels to tramp with the transfer of weight
 
My 2000 4.6 P38 has developed a vibration and (as a relative novice) I don't where to start looking, so some help would be greatly appreciated.

It happens when decelerating above an indicated 70mph. So, for example, if I go up to 70 and then take my foot off - nothing. But, if I go up to 75 and do the same then the vibration starts until I get down to 70 when it disappears.

Vibration can be felt through the handbrake, gear stick, and especially through my feet :) There's also a low growling sound - which if you weren't listening for it you probably wouldn't notice.

Tyres are in good nick and were new about 18 months ago (Scorpion STs all round). Car has been serviced regularly, but not sure if transmission or gearbox fluids have been changed recently. MoT was a couple of months ago at a reputable place - no advisories. Note that the vibration appeared before the MoT and has very slowly been getting worse.

The question is - where do I start? Or is it best to just book it in??

It's the new Nanny State speed limit advisory system installed on your last MOT. As you know the limit is 70 mph, any more and just like the anti stall warning on an aircraft you get vibration and if the overspeed is excessive it growls at you.:rolleyes:
 
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