the drums have O Rings under the piston guide that are not in the normal kit, and MB does not show them at all, if a problem comes up ( dropping out of 4 th or reverse issues SOMETIMES < not all the time -- they expect you to replace the drum ( 6 /7 hundred each ) BUT a kit is available for this repair it intalls a drilling of the riverts in the drum removing the piston ( Note you must funnel drill the piston so as it is not held up ( reducing clutch pack clearence ) it is all in the spceial O Ring kit directions,

The o rings under the drum that is steel are heat damaged over the years ( they dont move at all just sit on the one spot ) and turn into stone, than a massive oil internal leak starts to happen when the gear that uses the clutch in employed high gear in some cases does not even engage after a rebuild < we have fixed many units from other Repair shops that could not figuer this problem out -- if you do it yourself i believe i have good set of directions about the drum O rings -- jz