Have you tried to clear the rod seal? Here is a Lippert reference for your issue: http://www.lci1.com/images/Flyers/LI...-locations.pdf
Over time the shaft accumulates dirt and, when extended for prolonged periods without proper maintenance can pit. These situations can erode the effectiveness of the bottom seal which is the most likely place for an external leak.
Suggestion; With a soft absorbent cloth, a can of silicone spray and a soft shaft cotton swap. Fully extend the leaking shaft. (you might have to put blocks under the other side to accomplish this.) Spray the shaft and wipe it clean. Inspect for surface damage such as scarring or pitting. If the shaft is in good shape turn the spray on the bottom seal and blast any debris out. Use the swab to make sure it is clean. Also make sure all three seal retaining bolts are tight. You are dealing with aluminum so easy does it. With everything cleaned up you can cycle the gear and possibly clear any debris that may be under the seal. If it leaks after that you probable have a bad seal. If pitting on the shaft did not cause the leak then it is most likely that hard hook ups did. If that is the case you will need to replace it. Of course you will want to check the hose connection as well. Fitting wrench is needed there. Hope this helps.