My 5.0 sc FFRR, has developed a vibration (heard and felt) at 4000rpm in any gear. I took it to an Indy and demonstrated it on a test drive. After weeks of tests it was diagnosed as a supercharger issue which was then replaced.

After a month at the Indy and Immediately on driving out the same vibration is present. I was told to run it in for 1000km and then bring it back.

This problem doesn't seem to be getting worse, but can be felt by all passengers and is quite annoying. It first occurred after doing a major service at 75000km. I'm unsure if this could be related.

I believe it is a driveshaft issue, as it doesn't occur when revving the car in neutral.

Any ideas? Any input will be greatly appreciated 😁

does it feel/sound like driving over a cattle grid?

if so might be the torque converter

Unnecessary quote removed

hi docd

that sounds to me like a fuel pump issue. i.e. your fuel pump is getting tired and cannot pump sufficient fuel at higher rpm.

i would start by replacing the low pressure fuel pump and then going from there. that "1000km driving" is not going to improve anything. whatever your indie did in that month, they didn't fix the underlying issue.

Robert wrote:

does it feel/sound like driving over a cattle grid?

if so might be the torque converter

It does feel a bit like a cattle grid, the entire vehicle vibrates. Thanks guys I'll have it checked out, and will keep you informed.

I don't know whether trying it in sport mode if you have one or manual will get the torque converter lock up clutch or valve body doing something different but no harm in trying. RRPhil is your man for transmissions.

No difference in sport or normal drive mode, it banters from about 4000 to 4500 rpm then settles again.

if it's the TC you might try a total gearbox flush including the TC. That's about two liters more oil as the gearbox allone. It did it for me once.

Have you confirmed, that when you get the vibration, ,if you were to manually change down the gears, to say a higher revving gear, you get more vibration? If it's at the speed that 4000rpm comes in, and if say bringing the engine speed down, it still vibrates, then, surely the vibration, is something other than the engine.
On your service, were any tyres or wheels swapped? Any parts replaced, that we are not aware of?
If say 4000rpm, equates to say 90mph, in top gear, if you were to go into manual mode, and hold say 3rd gear at 4000rpm, you might be doing 60mph, and not get the vibration. But the engine is still revving at 4000rpm.
Do you feel vibration through your steering wheel? Or through the seat, or more severe? Like the dash rattles?
Sounds like something has been worked on at the service, and not replaced/refitted properly.
When you see off the pedal, how long does the vibration stay?

This may be a bit off-base, but are there any flexible joints in the rear propshaft?

Reason is many moons back I had a Ford Granada 2.8i Ghia Estate and one time we were driving down the M6 when I felt a vibration at a certain RPM range, when i got home and got it over the garage pit, I discovered that the rubber flexible joint between the gearbox putput shaft and the propshaft flange had split between two of the 3 sets of bolts holding the propshaft to the gearbox

I'm not sure if there are any flexible joints on the RR propshaft to the rear wheels but it might be worth checking for any cracks.

This is where it had split on the Granada, Alternate bolts go through the Gearbox output flange and the Propshaft Flange.

If it's engine speed related in any gear then it can't be propshafts or driveshafts or fuel pump....They do not move at the same speed as the engine in different gears... AFAIK the TC issue happens at lockup speed and that isn't anywhere near 4000rpm in an SC...

A near impossible fault to diagnose on a forum... you need a good mechanic to work their way through the problem...

As you have found out it's best to get some type of guarantee about the problem before anyone else just starts guessing at the problem, if they diagnose an item and it isn't the problem who is going to pay...???

Certainly don't pay any bills until you have test driven the FF...  Pete

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I was thinking if he is running this up to 4k rpms often the vibration could be passengers shaking in fear. That's in the "holy crap" range for me.

Taking it in to a gearbox specialist on Monday, will keep you all informed.

doclees yesterday when I was trying to hit 4K rpm in 4th gear to see if it's the same vibration, had me breaking many road laws. We won't even talk about 5th and 6th.