I've got this sort of vibration that comes in at 55mph...
They can make all the difference between a pleasant driving car and something horrible! Even the smallest wear, stiffness, or misalignment can cause an incredable amount of vibration through the car.
Just changing the Universal Joints can put a shaft out of balance - please note that unlike the halfshaft UJs, the ones in the propshaft should not be set tight. The type of propshaft you have fitted determines the cure.
Change UJs, rebalance, and refit.
Check for any broken straps and that there is no wear in the pin which fits into the prop end - a worn pin means the prop is scrap as it will not balance on the car even though it may balance on the machine. If all is OK, change UJs and rebalance.
Check for wear/play in the joint and that the UJs are in line with each other. (When you look down the length of the prop, the UJs should be sitting exactly above each other). If OK, change the UJs and rebalance.
Check for wear in joint. If any wear shows, have sliding joint from Marina/Dolomite welded on, fit new UJs and rebalance.
Propshaft Lengths (Working Length)
|Herald with Overdrive (3 rail)||46.5"||1.18m|
|Herald with Overdrive (single rail)||45.5"||1.16m|
|Vitesse with Overdrive||43.5"||1.10m|
|Spitfire I - IV||41.25"||1.05m|
|Spitfire I - IV with Overdrive||38"||0.97m|
|Spitfire 1500 with Overdrive||37"||0.94m|
|GT6 with Overdrive||35.5"||0.90m|