Engine/Drivetrain Vibration Issues

[jondee86]

If the vibration does not happen with the gearbox in neutral, then
it is safe to say that the problem lies further forward. That it only
occurs when decelerating probably rules out an engine imbalance.

The fact that the vibration stops when you touch the clutch pedal
or throttle, and that it only occurs at certain rpm's, indicates that
you may have a resonance problem.

When the car is decelerating, the momentum of the car is placing a
load on the engine and gears. Each time the engine fires, it unloads
the drive train. This causes a cyclic torque reversal on the gears and
the clutch, taking up the clearances first in one direction, and then
in the reverse direction. At certain frequencies this can cause
rattling of the gears and/or the clutch plate sprung centre.

This type of problem is more likely if the engine is fueling while on
the overrun (decelerating). That is why I asked if your ECU supports
fuel cut on closed throttle. Some people have found that solid centre
clutches cause gear rattle, and changing to a sprung centre solved
the problem.

Did the vibration start/get worse when you installed the 6 puk clutch
or the lightweight flywheel ??

Cheers... jondee86