Does anyone know if the upper drive shaft is physically different between an X and XR they are different part # or just heat treated different. have drive apart wanted a stronger shaft. THANKS

They are interchangeable. I don’t know the reason for different part numbers.

Looking parts up at BAM, only difference in the part number is on the XR and it ends in T02 which just indicates a different vendor has made it of such thing

Get with George at AADS, he has improved a lot of the design and his don't break like the factory parts.