Dave, you are not hurting anything to run on them for now. Do replace all 4 at the same time.

 

Disco is only 4 months old for me... Ive been working on the 60k full service... I think I used the wrong terminology as its not "rough" just could feel slight vibration or looseness ... anyway, Im going to have drive shaft rebuilt since it is in fact the stock one with no grease zerts on the u-joints connected to the cadron joint... on inspection the driveshaft itself and joints were not loose at all but I could slightly rotate shaft about 1/2" total 1/4" each way... and could hear gears touching as I did so in the transfer case... Im doing all that on next monday when Im off... anyway I did grease what was greasable and there is a noticeable smoothness added now :-)

 

late followup but maybe it will help others.... it was my front lower ball joints and cause flat spot in tires... but went away and grinding noise all GOOOD!