I have a 99 R1100GS (72,000mls) and just did a full spline lube and noticed the UJ at the final drive end is shot (notchy) so am in the market for a used one.
The general consensus seem to be that 1100RT drive shafts are the same but after ordering a UJ from an RT I can see they are different as per the pic. Mine is the bottom one with the splines cut all the way to the end of the shaft.
I am talking to another gentleman who also has an RT drive shaft and compared it to my UJ and he agrees his is not the same as mine either.
I checked with Bob's BMW and they said the 1100RT should be the same. All the microfiche agree.
REALOEM.com also syas the 1100RT should fit.
It did not appear that my GS had been apart before so I am very confused as to which used driveshaft to pursue.
I have a guy who has a 2004 1100S shaft and he says the UJ looks exactly the same as my UJ but I don't particularly want to buy a whole drive shaft just for the UJ but am happy to buy it if the whole shaft works.
Any enlightenment would be appreciated.