400 Axle, Hub and Brake Ratings

manyman297 · August 31

I’ve been dealing with a braking issue that I just can’t seem to figure out…it’s become personal at this point.

I’d link to the previous discussion but my question now doesn’t really pertain to any of that.

At this point I’ve replaced the brake assemblies and have pinpointed my braking issue to a magnet/hub issue where I believe the grooves caused by magnet wear are causing the brakes to hang up on application and not completely release…almost like the grooves hold the magnet in place. I figure by replacing/turning the hubs I’ll have effectively brand new brake components and that SHOULD be the fix I need.

I’m struggling to find a local shop that can turn my hubs. They can turn the outer part just fine but the magnet surface seems to be where many shops say they can’t do. I’m still calling around and hopefully can find a shop that can do it.

As a plan B I started shopping around for new hubs. The hubs used on our 2021 400 are rated for 4,000lbs and are extremely hard to find and are expensive ($150-300 per hub). Most 10” hubs are rated for 3,500lbs and are cheap and readily available.

In looking at Dexter’s manual it appears both 3.5k and 4k hubs use the same bearings (part numbers are identical)…which begs the question, wouldn’t 3.5k hubs works just fine in lieu of 4k hubs? To me the bearings would need to be beefier to support the extra load, right? I know this isn’t the safest conclusion to come to and I plan on emailing Dexter. It just seems that maybe they have a separate part number for 4k hubs in order to avoid confusion when dealing with a 4k axle?

Anyway, just curious if anybody here has managed to safely use 3,500lb hubs on their 400. It sure would make buying new hubs more attractive if I can’t find a shop to turn my existing hubs.

qhumberd · August 31

I have the 2019 400 and have noted the chart seeming to show identical cup and cone part # for the 3.5 or the 4 K axle.

I am wondering if Dexter can recommend a procedure to refurbish your existing hub? Or suggest further diagnostics? I read that you had done a lot without success in understanding the problem. I seems that finding a better tech might be less expensive than complete replacement.

Image: https://us.v-cdn.net/5021717/uploads/editor/5y/gfffqjwpdkeq.jpg

MuttonChops · August 31

The inner Drum Surface is called the Armature.
A special Drum Turning Lathe Tool is required . . . < $200 for a shop to purchase.

One of your more local, full service shops might be willing to invest in the tool if they have a reasonable trailer electric brake service operation. Another option would be local machine shops that support industry/agriculture. I once had a recreational boat rubber shaft repaired in a big machine shop . . . they gave the project to one of their super old techs that mostly did new guy training.

youtube video on Armature resurfacing

Reference:

Image: https://us.v-cdn.net/5021717/uploads/editor/36/wln3lues5de1.jpg

manyman297 · September 1

Yeah, the better part of me says to just hire a tech…but I’m an idiot. At this point the problem has to be with the drums. They stick going forward but are fine if I reverse and activate the controller…no sticking. I’ve ruled out electrical issues and confirmed this with discussions with a mechanic.

@qhumberd The doc you referenced is the same one I found. You’d think the hubs can support the same weight if the bearings used are identical…that’s where all of the weight is being supported…but I’m no engineer. I need to call Dexter.

@MuttonChops Thanks for the info. Now I know what to call it when asking shops if they can machine it.

If the grooves worn into the armature surface are the culprit I wonder if grinding down the grooves in the magnets would temporarily eliminate the catching? My theory is the magnets are lodging themselves into these grooves upon activating the brakes…and if I just slightly rotate the wheel backwards it instantly releases. I may try this before I do anything further. I’d like to just get this back on the road for the last few weeks of this season and then deal with a proper long-term fix next spring.

Horigan · September 1

If the brakes are working in reverse, have you tried swapping the drums to the other side?

Grumpy_G · September 1

Apologies, I don't remember if that was mentioned in your original thread: Did you check the orientation of the brake shoes ? The shorter shoe goes towards the front.
I can't imagine the grooves being the cause of the issue, I have a sizable grooves in my armature surface with the "matching" magnet as well. No problem with the brakes.
Any chance there is voltage bleeding into the brake wiring ? You could test that by raising the wheel in question off the ground, turn it while applying the brake so it "sticks", then disconnect the trailer plug and trailer battery. Which brings up another idea: Check the trailer brake output at the connector in the truck for stray voltage as well.

manyman297 · September 1

@Horigan Yes, orientation is correct. This problem started with the original brakes. New assemblies were checked before installing.

@Grumpy_G Definitely in the correct orientation. Regarding voltage bleed: I had thought of that but the fact I can barely nudge the wheel backwards and it immediately releases tells me this is mechanical unless I’m not thinking of something less obvious. I’ll definitely check the output on the truck just in case though.

It’s disconcerting that you have the same grooves in your brakes but they work fine. This is definitely the most mysterious mechanical issue I’ve had to deal with.

What also makes this seem less like anything electrical is the fact I can use the manual override on the brake controller in reverse and it releases just fine. It’s something about going forward that causes this binding.

MuttonChops · September 1

manyman297 said:
. . . disconcerting that you have the same grooves in your brakes but they work fine.

If it was 'my trailer' . . . I'd just replace the magnets.
No data to say that is best of course,
just am thinking a new flat magnet surface will conform/adjust to the grooves all armature surfaces have.

manyman297 · September 1

I have new magnets from the new assemblies but didn’t want to wear the same grooves into them. That’s why I’m wondering if grinding down the grooves on the existing magnets would be a fairly easy next step to troubleshooting. I’m thinking a grinding wheel on an angle grinder would suffice? Anything to avoid disconnecting the magnets once again.

MuttonChops · September 2

manyman297 said:
. . . thinking a grinding wheel on an angle grinder would suffice?

While I understand the temptation, and might even try that myself, do question how wise it is as you have zero control on how planar the final surface would be . . . while a lathe operation will insure a planar surface. A non-planar issue top-2-bottom or side-2-side could be more of an issue.

Which is why I'd just try new magnets . . . letting them form to the drum grooves. . . .

manyman297 · September 2

@mutton Yeah, I see your point. I need to pop the drums off (for the 4th time) and see where the magnet needs to be ground down. I believe the bottom corners are the culprit but again, I see your point about how unruly the grinder might be.

My fear of using the new magnets is that I’ll eventually be in the same situation once the grooves are worn into the magnets (assuming this is the real issue here). Grinding the existing magnet corners just enough to prevent any type of binding that may be happening in that armature surface groove seems to be the next cheapest option. Worse case I can cut the wires, remove the magnets and use a belt sander if needed.

tabiphile · September 2

If it was mine, I'd cut to the chase. I do not like turned drums on anything. For the relative minimal extra cost, I always replace drums and rotors. Brakes are not something you want to fool around with. Start with fresh OEM parts. Do it once and do it right. I learned that lesson many years ago on good cars.
I have never seen a problem quite like the one described here, but if fresh new parts does not fix it, there will not be many more rabbit holes left to go down.
I find myself wondering what sort of brake controller is being used here?

manyman297 · September 2

@tabiphile I hear you completely but hubs for these axles is $150-300 EACH. These aren't run-of-the-mill 3500lb axle parts that are dirt cheap hence the crux of this thread. If I can use 3500lb hubs on this I'll just buy new hubs. If I can't then $300 in new hubs plus the $250 I just spent on new assemblies starts to sting.

I'm putting in a call to Dexter today to see if I maybe they give dedicated part numbers to 4k axle parts just to avoid confusion and maybe they're identical to 3500lb parts.

I'm almost certain the brake controller isn't the issue. I can recreate the problem simply by puling the emergency brake pin, rotate the wheel forward to engage the brake, plug the pin back in and still have to slightly back up the wheel to disengage the brakes.

manyman297 · September 2

Just spoke with Dexter. Lady I spoke with wasn’t sure so she spoke to another tech and he confirmed that 3500lb and 4000lb hubs are interchangeable. You just can’t use a 3500lb assembly (backing plate, shoes, etc) on a 4000lb axle. So I should be fine buying new 3500lb drums.

tabiphile · September 3

Brake jobs are one of those things that go much better and far more quickly when you have fresh parts. And, even here, the cost of the parts are relatively low. Good that you are getting this figured out. Hopefully everything goes back together quickly. Kudos for taking this on. A lot of people shy away from brakes and bearings and yet they are an incredibly simple thing to work on. Unless you start turning drums and rotors....then it gets into a place that requires tools most of us do not own.

qhumberd · September 3

Fingers crossed this solves the brake sticking issue. Please post when you get a resolution.

manyman297 · September 3

@tabiphile I try and DIY everything which has its pros and cons. I was actually terrified of having to take the camper into a shop because I know how notorious they can be with both the quality of work AND keeping the camper for weeks at a time.

I also try and look at these challenges as teachable moments. I knew a little about how these brakes work but now I feel like I know more than enough and can use this knowledge in the future. Sure I spent 20 hours and $400

@qhumberd I'll keep you posted and update this thread.

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400 Axle, Hub and Brake Ratings

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2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"