First and second gear are bands. Third gear and fourth are clutch packs. Identify which gear you are having a problem with. I think both bands have externally available access to the servo piston seals which would probably be your problem although I have seen two 190s break the ends off one of the bands.
All of this can be determined by an experienced tech by removing the valve body and applying each device with compressed air though the appropriate channels. The bands are visable from this position. Their replacement requires complete disassembly though.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician