Everything externally accessible:
B2 cover, governor cover, B2 band reaction piston, etc.

Or leave well enough alone and cross your fingers.

Sweeties 300D has never been idled, and doesn't leak a drop. My former SDL sat for, in my estimate, 10 years, and leaked from every port on the transmission when I got it. The o-rings and seal "rubber" had turned to glass, and actually cracked into many pieces during removal. And no, running for a while with full fluid (DexIII, but no magic juice) did not "rejuvenate" the seals--they had to be changed.

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k