I'm getting a factory second 4220 for $372. I think full MSRP is about $450. Supposed to fit my current motor/gearbox.
In all honesty I believe the failure was my fault. My camper has been sitting unused for a year. It's always covered with a Classic Accessories cover that keeps most of the rain off. I put small plastic buckets over the front motors. But the jacks haven't been exercised in that years time. The inner tubes corroded to the outer tube. I beat on the foot of the inner jack with a sledge hammer so much that I cracked the weld on the foot. But it came out, maybe 1/8" inch at a time at first, then more later. That's after a couple days of soaking with Kano Kroil and WD40 rust penetrant. The acme screw was in good shape. I lubed it with marine grease and Nuclear Grade Nickel Never Seize. I just put it back on the camper and it seems to be good to go.
The other front jack came apart a little better. However the acme screw is locked up inside the bottom assembly that is not serviceable due to it being crimped in place. Pipe wrench with a cheater pipe and hammer was no help. That is the one I am replacing.
I think it would be wise to talk to Customer Service at HappiJac and order some spare parts for the future. Particularly the parts that are unique to the non-current jacks, which is likely most of them. I would recommend at least the disengagement assembly, including the lever and the small delicate tab opposite it, the thrust bearing, and the O ring.
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