"The front one is an easy replacement w/o removing the d/shaft."


Loosening the 42-46MM nut/coupler will give you enough BackSlide room to
R+R the front disc.







I'd visually inspect the "Centering bushing" and if there are no signs of distortion
/wear, just re-lube it.
R+R of the Bushing will require the removal of the Driveshaft,for sure.

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'84 300SD sold
124.128