Diagnose Vibration That's Worse When Coasting

[ukkid35]

It's not a violent vibration, more like a rumble, but doesn't sound like a wheel bearing

If I take the car out of gear at high speed it seems to get more pronounced

I presume this means it must be from the back of the RWD car

Where should I look? And what do I look for?

• Propshaft
• Diff
• CV Joints
• Wheelbearings

It would probably be cheapest to replace the wheelbearings first to rule them out, but I'd rather identify the cause then fix it, than replace things until it stops

Any suggestions?

[ssray]

Which car?
Could be a rubber donut type thing halfway along the driveshaft

[ukkid35]

ssray said:

Which car?
Could be a rubber donut type thing halfway along the driveshaft

TVR Cerbera, the vibration is mainly felt in the seat rather than steering wheel or pedals

[E-bmw]

ssray said:

Could be a rubber donut type thing halfway along the driveshaft

^^^^ Wot 'e said.

[liner33]

If its the driveshaft you would feel it through the gear lever

Hard to say what it is since it could be some many things need to get it oin the ramp and check it

[ukkid35]

There's no rubber isolator on the propshaft, but maybe the bolts have come lose, I'll check that - thanks

[Clifford Chambers]

E-bmw said:

ssray said:

Could be a rubber donut type thing halfway along the driveshaft

^^^^ Wot 'e said.

They make a right old mess it they let go too.

[Jazzy Jag]

When you are coasting, do you have the clutch depressed ?

Could be clutch release bearing, gearbox bearing or flywheel spigot bearing?

[ukkid35]

Jazzy Jag said:

When you are coasting, do you have the clutch depressed ?

Could be clutch release bearing, gearbox bearing or flywheel spigot bearing?

Thanks, happens out of gear both clutch depressed and not - both release and pilot bearing are new, and I rebuilt the gearbox a few years ago

[Jazzy Jag]

ukkid35 said:

Jazzy Jag said:

When you are coasting, do you have the clutch depressed ?

Could be clutch release bearing, gearbox bearing or flywheel spigot bearing?

Thanks, happens out of gear both clutch depressed and not - both release and pilot bearing are new, and I rebuilt the gearbox a few years ago

When you are coasting, the loading and side loads on gears reverses so anywhere with beveled gears will load up the opposite sides and thrust washers ,if fitted.

Diff side load on the sun crown wheel. Pinion will get pushed outwards. Any beveled gearbox gear will thrust in the opposite direction.

Have you said what car it is?

[stevieturbo]

Are the wheels bolted on tight ?

[annodomini2]

Diff mount come loose?

[ukkid35]

Now it's on axle stands I can see that there's enough play in one of the inner CV joints for the boot to visibly twist when turning the wheel back and forth

Any chance that is not the culprit?

[Zener]

If one of your CV joints as rotational play like you describe its fked , got be changed regardless