940 Holiday

[Rversteeg]

I have been looking for the official Volvo service bulletin regarding this rumble but could only find its text:

Driveline Take-Off Vibration: Shimming May Be Required.
From Volvo Technical Service Bulletin 45/102 Jan '91. [Symptom:] Take-off vibrations at low speed, especially with high acceleration and/or heavy load, can occur in some cases.
[Solution:] Before you conclude this is the problem, make sure your engine and transmission mounts are in good shape. The level of driveshaft vibration can be reduced by changing the vertical position of the center support bearing. The support bearing is bolted to a bracket, which in turn is bolted to the underside of the car body. Adding shims or washers between the car body floor and bracket will shift the bearing down. Adding shims inside the bracket between the bracket and support bearing will shift the bearing up. Best results differ from car to car. Start with a change of 6mm (1/4") upwards. If results are not acceptable, try positions from 5mm (3/16") downwards to 12mm (1/2") upwards from the original position. Note that clearance between drive shaft and fuel lines must be at least 20mm, and between drive shaft and the fuel tank at least 16mm. Shimming upwards should not exceed 12mm (1/2") and after re-positioning the center support bearing housing should not contact the floor pan.

To get a visual idea of how the axle moves during driving:
https://www.youtube.com/watch?v=OFlZZ96poIM

Rob