I had this happen too. Cant find my full response right now, but will try to remember to track it down in the next day or two.Was topping up engine oil the other day, and noticed my $2 fuel filter on my extended front diff breather is 1/2 full of diff oil.
Should I be concerned?
Whats a possible cause?
They cost ~$1ea, replace as needed,,, the ones on my truck are ~15yrs old, never been replaced.I'm not a fan of using cheap fuel filters at the end of a 'vent line'. They are designed to trap fairly small particulates and as such can clog easily from dust or a mist of oil that is expelled over time as the diff heats up and pressurizes. As the filter becomes saturated...the issue is exacerbated.
Filter/Muffler is like $3-$4 on ebay, and are designed to flow AIR. Never replaced mine either in 19 years. People use fuel filters because they are too lazy to source a more suitable item for the job, not because of cost hopefully.They cost ~$1ea, replace as needed,,, the ones on my truck are ~15yrs old, never been replaced.
Your fuel filter is also opaque, the filter in your trans...you can not see, the fuel pump sock is out of sight. None of these things need to be constantly checked. Just check them from time to time. Neither 'Tools' or I have seen a need to change either item in many years. IF you do water crossings often or are neglectful about changing out diff gear lube or servicing your birfields...then yes you might check whatever filter system you choose regularly.The clear fuel filter gets my vote - it's right on the firewall and I can and do look at it all the time. The clear aspect makes inspection constant and allows me to always be informed. An opaque option is inferior in that regard, and I don't see a need to switch. Just my two cents, I'm with Tools.