Being a Southwest VA farm boy in my former life, I have used John Deere tractors all my life. Got an LX-280 with 42" mower for yard in suburbia. Have noticed a small oil leak on the left side (from driver's seat) of the transaxle case, approximately from the busahing or O-ring of either the brake lever or belt drive on top of the case. The Hydrostatic reservoir never uses oil. Engine oil is fine. So, where is this oil coming from. Local JD dealer thinks it is air in transaxle. Cannot get the plug off to left of reservoir filler to check. Any ideas?

Hi,
Deere does have the manual online at:
OMM152799_I4
And tells of the reservoir and the type of oil. It is a serviceable unit and the transaxle must be filled at the yellow cap if serviced; it will not refill from the reservoir.
You can find a parts breakdown at JDParts at:
John Deere - Parts Catalog
I would keep an eye on it since small leaks can be difficult since the oil could be blown be the cooling fan on top of the unit.
Peace,
Clarke