I often wonder why people keep saying that you should put ATF in that manual transmission, it makes no sense. Won't it even affect transmission performance? I never had problems with my manual until I tried ATF!!
Recently, I couldnt even downshift from 4 th gear to 3 rd Gear.
Perhaps I have a damaged Synchro, but before i tear down the transmission, i would like to put Gear Oil in it and try it..

83 240D Manual--Do I put ATF or Gear Oil in Transmission?