That is the same thing that i have om our 2188.I have changed the dipstick once and installed a breather by the fill tube three years ago to stop this.This year i still have the same problem with the dipstick so i took the filltube off to see what is going on.The fill tube is rusted out from the inside out from moisture at the first bend.The moisture is from the oil temp changing from cold_hot,hot_cold(will always happen with any oil or gearbox) and it can not get out from that long tube.I am going to try to weld a breather at the first corner and by the top of tube where you fill it so the moisture can get out. Guys look at that fill tube at the first bend form gearbox you will not believe the rust inside. Thanks for your input The Kid