Happijac lubrication

jjinatx wrote:
Update on my jack saga. It turns out my rear jacks are 4100 models, not 4500 models like the fronts. The 4100 is quite a bit different internally and I'll post some pics soon of the insides of them to add to this great thread. I also see evidence of lubrication on the 4100's and in fact did not seem like they needed re-lubing at all.

Bad news. The 4500 that had been given me problems and had frozen up appears to need replacing. Even after I re-lubed it and can turn it with my fingers on the bench, when it under load coming down it binds up occasionally. When it does, I have to unload some of the weight by lifting a bit on the opposite side. My best guess is that the mechanism that is preened into the top of the lower leg that the acme screw threads through is worn and binding under load. But before I order a new one, I'll take it apart once more for closer inspection and maybe replace the thrust bearing in case that is the problem.

I have a bit of a dilemma when it comes to replacing it. I can get one 4500 for about $350, or a pair of 4600 jacks for about $550 (the place only sells them in pairs). Is the 4600 worth upgrading to from the 4500? Is the only difference between them the quick released? Or is the mechanism stronger/better? Do I want to spend $200 extra now to save $150 just in case the other one goes out too?

If I do have to replace the jack, I'll cut it open and post some pics of the innards of the lower leg to this thread.-jj