Kubota F3060 4x4 (3600 hour) mower is built basically similar as many small Kubota lawn tractors are (at least the parts are very similar) but it's assembled to be driven "backwards".
It had a hard to find HST oil leak, which I thought was in the HST itself but it turned out to be a very hard to spot hairline crack (above the normal oil level) in the aluminum 2-speed range selector housing!
The leak seemed intermittent and had been there for quite some time but I lucked out and discovered the source of it after HST oil change, prior to firing up the engine when the HST oil level was still higher than normal due to air in the system filter, piping etc.
The air gets purged as soon as the low pressure hydraulic pump begins pumping and the HST oil level drops to normal.
In my opinion this hairline crack in the aluminum housing was caused by uneven stress from the large frame bolts.
It was tough to locate the crack since was above the normal oil level!
The new 2-speed range selector aluminum housing casting has been reinforced by the manufacturer and I ended up making couple of round shims to go in-between when bolting / torquing the steel frame to the aluminum housing.
Housing, item 010 below had a hairline crack by one of the large frame mounting bolt threaded holes:
A long hairline crack is visible about 3/4" right side of my finger:
New housing in place - the new shims are visible in-between the frame & housing if you zoom in closer:
It's nearly impossible to see the area in question when the frame, hydraulic hoses etc. are all assembled back in place and will be eventually all covered with a fender on top:
It's all back together and working great - so far so good, no leaks after about 20 hours of use!
PS. Put the ROPS in storage due to pretty level property!
It had a hard to find HST oil leak, which I thought was in the HST itself but it turned out to be a very hard to spot hairline crack (above the normal oil level) in the aluminum 2-speed range selector housing!
The leak seemed intermittent and had been there for quite some time but I lucked out and discovered the source of it after HST oil change, prior to firing up the engine when the HST oil level was still higher than normal due to air in the system filter, piping etc.
The air gets purged as soon as the low pressure hydraulic pump begins pumping and the HST oil level drops to normal.
In my opinion this hairline crack in the aluminum housing was caused by uneven stress from the large frame bolts.
It was tough to locate the crack since was above the normal oil level!
The new 2-speed range selector aluminum housing casting has been reinforced by the manufacturer and I ended up making couple of round shims to go in-between when bolting / torquing the steel frame to the aluminum housing.
Housing, item 010 below had a hairline crack by one of the large frame mounting bolt threaded holes:
A long hairline crack is visible about 3/4" right side of my finger:
New housing in place - the new shims are visible in-between the frame & housing if you zoom in closer:
It's nearly impossible to see the area in question when the frame, hydraulic hoses etc. are all assembled back in place and will be eventually all covered with a fender on top:
It's all back together and working great - so far so good, no leaks after about 20 hours of use!
PS. Put the ROPS in storage due to pretty level property!
Last edited: