1. Vehicle vibration due to a propshaft out of balance
A propshaft vibration is very similar to a wheel vibration and may be caused by one of the following:
- A new vehicle where there is a driveline fault.
- A modified vehicle where angles or installation are incorrect.
- An old propshaft with worn components.
- A balance weight falling off.
- Accident damage to the propshaft or mating flanges.
- A poorly repaired shaft
2. The driveline vibrates at a certain speed
Most propshaft vibrations are worse within a 15-25mph band. i.e. comes in at 50mph and goes at 65mph. If the vibration is over the complete speed range either the propshaft has been bent or damage has occured to other transmission components (gearbox or differential).
3. There is a clunk when the clutch is released
This can be due to worn components in the propshaft either a universal joint or if fitted, sliding splines or wear between splines and connecting flanges when a centre bearing support is used.
A propshaft with worn components cannot be successfully balanced to known tolerances
4. Is there a standard for propshaft manufacture?
There is an Internationally recognised standard for the dynamic balance of rotating bodies which include propshafts. It is not neccessary to balance a propshaft to very fine limits if the application does not require it. It is as important that the propshaft is straight with minimal runout on tube and forgings as it is to dynamically balance the shaft. The shaft should be balanced at a set speed equivalent to the speed that the application will spend the majority of its life doing. It is pointless balancing a shaft at 5000rpm if it will spend most of its life spinning at between zero and 3000rpm.
The standard for the dynamic balance of propshaft is generally accepted as follows:
- ISO 1940 G40 (VDI 2060 Q40) for shafts with slight wear
- ISO 1940 G25 (VDI 2060 Q25) for new shafts
- ISO 1940 G16 (VDI 2060 Q16) for special application
To certify that a shaft is within the recognised tolerance we must know the speed required, the weight of the shaft and which of the above grades is required.
5. Can a propshaft be made stronger?
In some cases it is possible to upgrade a propshaft within reason. A propshaft must be viewed as a "fuse" in the driveline. If the shaft is upgraded without consultation, premature failure may occur in other driveline components.
Propshaft tubing is NOT standard tube, it is made to a specification that controls straightness, ovality and wall thickness and allows a certain degree of flexibility.