I got a VW New Beetle 2000 with a 1.9 TDI ALH engine. The gearbox is a 02J/EBJ. The car is 19 years old and odo shows 232400km.
There is a strange sound for a very very long time, it was already the case when the car was only a couple of years old.
-> Click here to hear 5 different samples of the strange sound. The strange sound is at the end of each sample. Each sample is separated by a 2 sec silence.
Conditions to trigger the sound
- Decelerating only
- Only within the speed range 20km/h -> 5km/h. The sound appears only at 20km/h and below, and dies when the vehicle speed reaches 5km/h or less. Then the normal idle ALH engine sound comes back. With my wheels/tyres circumference of 1985.17mm, this means within 168RPM -> 42RPM wheel speed range.
- Only when decelerating slowly, in free wheels configuration (neutral speed selected with clutch pressing against the flywheel).
- The sound is of low frequency. Approximately the same frequency band as the idle engine sound itself.
- The sound is of oscillating nature. It oscillates as long as we are within the 20km/h -> 5km/h range, and then the oscillation dies.
- The duration is variable. Sometimes the oscillation lasts 2 seconds, sometimes 10 seconds. It actually depends on how long the car will stay in the 20km/h -> 5km/h range. If you succeed to make the car decelerate very very slowly and keep it in this range for a long time (in free wheels), the sound will last a long time.
Possible sound origins
- Silent blocks on the engine or elsewhere
- Imbalance in the drive axles
- Unstable gearbox output shaft or differential
- Wheel hub bearing
For sure, the sound is intimately correlated to the drive wheels speed but I don't know what part causes that sound. Any ideas?