Happijac lubrication

I had the same experience. The likely reason is the tubes are stuck is because there is a build up of rust and grit between both tubes. You are on the right track; it's a slow process. Try using a better quality penetrating oil applied from the bottom. Stand the jack upside down for hours. You may have to repeat this several times before you get results. I separated the pieces using two techniques (the trick is you don't want to hammer pieces so hard as to cause damage). 1) I locked the jack in a vise and tapped the foot of the jack to get some movement. 2) With all the gears removed you'll notice a hole at the top end. I used a piece of rebar about 1 1/2 times the length of the jack and tapped it against the inside of the foot. Once thngs start moving the effort required will decrease. Before reassembly I cleaned the tubes with acetone and steel wool. Upon reassembly I greased the running surfaces of both tubes (it's messy). The root of the problem is that the recommended lubrication method is not effective. Little to no oil gets into the tube area and over time moisture and road dust causes gunk inside the tube. Happijac owners are left with no joice but to disassemble the jacks every 2-3 years to clean and lube the tubes.