The motor and gear box should come off with some gentle tapping...If not that would be strange. I wonder if someone put the motor/gear box back on with some sealer..uggg.
My BF is 21 years old now. My jacks have been used 100's of times. I have serviced them 2 times, only the fronts. One broke the shaft keeper and was binding up. I ended up buying 2 new 4500's a couple of years ago. I have only serviced the rears one time.
Here is the link to HJ repairs....
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/22881036.cfmJim