So much for "HappiJac's Acme Screw Jack is the first acme screw jack with a redundant safety check system"One of my rear jacks failed, has no ability to raise/lower or hold up the camper, just slips. I'm glad it only takes one rear jack to hold up the camper or the TC would have went over. Switched to manual, no help as jack just makes a bump noise and slips with any weight on it. Took the motor off, all looks good. Anyone else experience this type of dangerous failure, what is the mechanism that is supposed to prevent the jack from collapsing under load ?????. Looks like I'm just going to replace with a new 4150.

There are a couple posts about disassembly, Take it apart and see what is broke. Could be the pin that makes the gears go around. Easy fix if thats the problem.

Yes, about the only thing it could be is the pin.Happijack disassemblyI took all of mine apart, re-greased them and put them back together.But, I don't think I have ever heard of the pin breaking before.

I reviewed those pics before posting, but thanks. It sure seems like the worm gear top assy has failed as I see nothing else that would allow the jack to retract itself back under load (without any shaft rotation). I'll take apart and see, but IMO this is a big time design failure.Update: It took all of 10 mins for me to disassemble the jack. The failure is as I suspected, the crimped in worm gear threaded assy block that is part of the lower tube has failed in a way that allows the long threaded shaft to slide through under load. I suspect the threads are deteriorated due to moisture. This means that all my Happijacs are subject to failure at any time. They were new in 2005 and oiled as suggested by HJ. I'll contact HJ to see if I can just send them in the lower tube and I'll pay for the repair.

I thought the 4150 is a ball screw, not an ACME. A ball screw will retract (backwind) under load unless the brake stops it. If the brake mechanism is broken, then it will retract. An ACME screw won't, too much friction to back drive. The brake mechanism is underneath the bevel gear, you can't see it until everything's apart. The brake is released by the crank (or motor) turning backwards - maybe something is stuck and not letting it reset.

THe 4150 is ACME according to the HJ site, but what's the difference vs. Ball Screw ? Either way, my 4150 failed under load and the long threaded shaft looks clean, so the problem is in the female threaded section and where was the backup they advertise?

HappiJac 4150 Problem | Good Sam Community

HMS_Beagle
Explorer
Dec 06, 2014
Jfet wrote:
HMS Beagle wrote:
Bronze ACME nuts are used for lead screws on machine tools, sometimes these things are run 16 hours a day for decades.

I never leave my cnc milling machine or lathe out in the snow and rain for months though...

Me neither, but that won't bother the bronze and he said the screw was shiny.

But for RAM TC - are you saying that the front jacks were 4150 ACME screw jacks on your camper? Which in your profile is listed as an AF 990? That seems like way too much for those jacks. My little Bigfoot had the 4500 jacks on the front (which carry a lot more of the weight) and 4150 on the back, it was listed by Bigfoot at 2200 lbs. My bigger Bigfoot is listed at 3000 lbs, 4500 on all corners. I think an AF 990 quite a bit more? Maybe AF under spec'd those...

Shop around the internet for those replacement jacks - prices vary a lot.
Jfet
Explorer
Dec 05, 2014
HMS Beagle wrote:
Bronze ACME nuts are used for lead screws on machine tools, sometimes these things are run 16 hours a day for decades.

I never leave my cnc milling machine or lathe out in the snow and rain for months though...
RamTC
Explorer
Dec 05, 2014
After my experience and learning of their expected lifespan, I'm proactively replacing my two front jacks with the new HJ "HD" 4800s, and I'll move the old fronts to the rear. Replacement jacks are reasonably priced, so I'm moving on.

No point in talking to HJ, they seemed to be aware of the 4150 problem before I wrote them.

I'll just pass on to HJ owners that their jacks are quite capable of failing internally and collapsing in without warning. Good luck, nuff said.
trail-explorer
Explorer
Dec 04, 2014
HMS Beagle wrote:
... But I think you would have more luck calling them and talking directly to a warm body. Its easy to blow someone off in email.

Agreed, I would call them up.
HMS_Beagle
Explorer
Dec 04, 2014
6 years for jacks is ridiculous, even in the notoriously bad RV business. But I think you would have more luck calling them and talking directly to a warm body. Its easy to blow someone off in email. In 6 years how much have they been used? For a lot of people that would only be only 20 or 30 cycles. Bronze ACME nuts are used for lead screws on machine tools, sometimes these things are run 16 hours a day for decades.
bigfootford
Nomad II
Dec 04, 2014
6 years? Damn I should be on my 2nd set....
Originals are almost 15 years old and running good... I use the******out of mine.
I have totally disassembled the fronts 2 times to lube and clean. 1 time for the rears.

Jim
Bedlam
Moderator
Dec 04, 2014
I know my Atwood tongue jack on my toy hauler lasted only six years before the parts wore to the point that the jack would bind with side force applied. Our camper jacks are just larger versions of trailer tongue jacks.
Glacier_D
Explorer II
Dec 04, 2014
Wow, I called HJ a few times about some of my issues and have had nothing but superb service from them. Maybe you should call and I bet they will help you. Find it hard to believe that they said HJs were good for only about 6 years.
Just had a jack motor rebuilt and Gary (I think that is his name) said that was early for a motor to go bad. Mine are 6 years old too. Mine are used in extreme conditions though and yes I have endured some problems with mine that I felt shouldn't have happened.
RamTC
Explorer
Dec 04, 2014
It's just as you wrote HMS Beagle. I contacted HJ via e-mail and they only answer questions selectively. Response was that the normal life span of a jack is 6 years and I should buy a new jack that has more capacity.

Good luck to anyone using these HJ's, they can fail internally without warning.
HMS_Beagle
Explorer
Dec 01, 2014
So the plate crimped inside the bottom tube is still there? Not moving past the crimps? If so, the ACME nut must be stripped. That is either a serious defect in manufacturing or a serious overload. They are only rated to 1500 lbs, a heavy camper unbalanced on one might exceed that. But you would expect at least a 2X safety factor before any catastrophic failure. The Happijac failures seem to mostly be the motor and drive train, or the ball screws freezing up. The ACME screw itself ought to be pretty bulletproof.