I know this thread is over a year old, but I thought it was worth sharing some input as I just went through this. I have a 18' flatbed that has dual 3500lb axles with brakes on both axles, nicer tires that I just replaced within the last 1.5 years, but I too wanted to upgrade my axles. I always knew with just my blazer on it was pretty much maxing it out (though I had loaded it way heavier before...not cause I wanted to, cause I had to). It's done the job since I've owned it. Blew a few tires here and there (the ones that blew were older) and I blew 1 bearing last year.
I contemplated just selling the trailer and buying another one that was already 10k rated (as mentioned above), but I have some time and money into this trailer already all within the last 2 years (brand new wood deck I installed, built my own drive over fenders, welded on d-rings, bla bla). So wanted to see how much it would be to just upgrade the axles. I ended up finding these guys:
https://thetrailerpartsoutlet.com/5k-5-2k-dexter-trailer-axle-5000-5200-lb-electric-brake-6-lug/
(you obviously need to pick the correct hub face/frame width axle for your application)
I ended up ordering these exact axles through ebay (still shipped from the same store) cause through ebay it was offering free freight shipping to my house. So after it was all said and done, I got 2 brand new 5200lb axles with brakes on both, with new leaf springs and u-bolts, shipping directly to my house for $950. Obviously I then had to get new rims (current rims are 15x6 with 5x5.5 pattern, and new axles are 6x5.5), but found some new 15x6 trailer rims with 6x5.5 pattern on amazon...got 5 of them for $250 shipped to my house. This will literally be a Saturday afternoon of unbolt current axles/leafs, bolt up new axles/springs, splice couple wires for brakes, have my current tires swapped over to my new rims, and then go. And added to this, my brother offered me $600 for my 3500lb axles with the leaf springs and 5x5.5 rims, cause he wants to build a trailer to haul his Camaro dragster. So for a grand total of $600 out of pocket I will now have a fresh 10k trailer. Sure, I guess I could have sold the trailer, (assuming I got a real good offer from someone) and then went and hopefully found a real good deal on a sale for a PJ 10k buggy hauler or something like that, and possibly spent in the end roughly the same amount (I'm a bit more realistic and realize it probably wouldn't have happened that way, and would have been more like $1500 or more out of my pocket in all reality, to go that route). But doing it this way means the trailer was modified to my needs by me (which brings me satisfaction), and I know it's a fresh trailer up to the task now, plus saved some cash.
Just thought I would share some info for anyone else that may stumble across this thread. My rims have already showed up, and my axles are being dropped at my house today. So hopefully this weekend will get the swap done.
