on my 129 I had a problem with a leak that I thought was coming from what looked like my passenger side seal. Without a lift I didn't want try dropping the axle myself so I took took it to my go-to guy on problems too difficult for me to do without the proper equipment. while the axle was down I had him go ahead and replace all the seals and still had the oil showing up in the same spot. I took it back to my servicer and he replaced the breather and the one seal again, it still leaked. I checked on my alldata subscription and found that this has been an issue and the fix was a 124 350 03 90 replacement breather. problem solved. so if you have the same issue, check that first.