At our Fall Tune-Up Clinic, it was discovered that the donuts (i.e. Rotoflex couplings) on my 1974 Elan had deteriorated to the point that one had broken in two. History is replete with disaster stories about what has happened when a donut lets go, and the half shaft goes flailing about under the car. Not wanting such an experience, I decided to replace the OEM half shafts with ones fitted with "U" joints.
Upon removing the original shaft, I discovered a "Something I didn't know". In the center of the yokes on the inboard and outboard drive shafts was welded a stud which was long enough that it entered the hollow center of the half shaft. The photos show these in place. Their purpose is clear. If a donut does break, the studs keep the half shafts in line until the car can by stopped. Therefore there is no flailing half shaft and no resultant damage.
I'm not sure when the studs and hollow half shafts began being installed on Plus 2's, or if they were provided on standard Elans. In either case, it would have been prior to December of 1973, the date my car was manufactured. By the way, my Elan +2 parts list shows neither the studded yokes of the outboard and inboard shafts nor a hollow centered half shaft.
