When a Land Rover is designed, the angle of the propshaft in relation to the two end flanges is carefully calculated in order that the vibration inherent with universal joints* is undetectable. The universal joints at each end of a propshaft are also set out of line, out of synchronisation to control this vibration, this is known as phasing.
Lifting the vehicle by raising the suspension alters the propshaft angle which often causes severe vibration. Aggressive mud tyres, noisy engine and transmission and the slower speeds associated with hard core off road vehicles usually masks the vibration and drivers often tolerate the additional drone or rattle from the shafts on overrun. A more road biased lifted Land Rover will most likely find the noise and vibration too obtrusive and will be keen to rectify it.
The most effective way to eliminate vibration is to fit a propshaft with a double cardan joint** at the gearbox end. Even Land Rover found this essential on the Land Rover Discovery 2.
Double cardan propshafts are successful vibration cure on vehicles around 2". Beyond 2" even the double cardan joint cannot always accommodate the angle without vibration.
* Universal joints working at an angle speed up and slow down during rotation.
** Double cardan joints have two universal joints joined by an intermediate shaft, the joints are phased or synchronised with each overcomes the speeding up and slowing down of a single joint thus reducing vibration.
It is a common misconception that fitting a wide angle propshaft will cure vibrations caused by raised suspension. The cause of the vibration is the angle of the shaft in relation to its end flanges, fitting a wide angle shaft does not change these angles. The vibration may seem reduced but this will be coincidental with a new heavier shaft in perfect condition.
Wide angle propshafts are necessary for vehicles fitted with very long travel suspension where on full axle drop out the original propshaft yoke will bind up straining the joints and ultimately locking the shaft solid which in extreme cases can literary tear the shaft in half.
A 32 degree yoke and joint will accommodate typical long travel suspension set ups on Land Rover based chassis using up to 11" travel shocks.