1863 hydro unit vent
 

I bought another 1863 yesterday, really nice shape only has 443 hours. I was cleaning it up today and sprayed it with simple green over the Hydro unit and was spraying it off. Later as I was spraying out from underneath the mower I found a Hydro vent piece. Checked the top of the unit and it was still in place. Did these Hydro units have more than one vent on them? I checked my other 1863 and could only find the one at the rear of the differential right at the top by the dipstick tube. I’m stumped?