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U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts

U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts

Item # APUBR-1
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Mount your round, 2-3/8" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included. Great Prices for the best trailer suspension parts from Dexter. U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts part number APUBR-1 can be ordered online at or call 1-800-940-8924 for expert service.
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  • Reviews (826)
  • Q & A (0)
  • Videos (2)
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Dexter Trailer Suspension Parts - APUBR-1

  • U-Bolt Kits
  • Camper
  • Car Hauler
  • Utility Trailer
  • Round Axle - 2-3/8 Inch
  • 5-1/2 Inch Long
  • 3500 lbs
  • 1/2 Inch Diameter
  • Dexter

Mount your round, 2-3/8" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included.


  • Attaches trailer axle to leaf springs
  • Includes:
    • (4) 5-1/2" Long U-bolts (176400)
    • (2) U-Bolt plates for 1-3/4" springs (117595)
    • (8) 1/2"-20 Hex nuts (12N)
  • Spring seats required for mounting axle to leaf spring sold separately


  • Axle diameter: 2-3/8"
    • Typical 3,500-lb axle
  • Spring width: 1-3/4"
  • Dimensions: see below

U-Bolt Diagram

K71-731-00 U-Bolt Kit for 3,500-lb Round Trailer Axles

Replaces APUBR-1

Video of U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Trailer Axle Long U-Bolt Mounting Kit Review

Speaker 1: Today we're going to be taking a look at the Redline U-bolt kit for mounting 3500 pound round trailer axles. These are 5 1/2 inch long U-bolts. The part number is APUBR-1.Now, when replacing your axle, it's a really good idea to also replace the U-bolts. These are a pretty cost effective item you can get and ensure that you're going to have excellent, excellent hold with your axle to your springs. You can see this is going on a floor spring pack. The opening on them is going to be 2 3/8 inch, so it's going to fit the outer tube diameter of our axle here.

It comes with the new lower plate, and also four new flange nuts that allows you to secure that end, keep everything locked tight, so you don't have any issues for a very long time.Now we're going to remove the four nuts on the bottom here that hold our axle down, and they hold the U-bolts here. When replacing an axle, generally you're going to replace these as well, just because these can kind of stretch over time. So, if these nuts won't come off, you can also just cut your U-bolts on each side.Now we're going to grab our new U-bolt kit and place these down and around, just like our old U-bolts were, and when we we'll replace the bottom bracket up on the U-bolts we'll see the hole here in the middle. That's meant for that nut to come down through, and then in each position we'll install one of the flange nuts.Now we'll go through and you're evenly going to tighten down our bolt. We'll get them snugged up first and then we can torque them.

For these nuts you'll want to use a 19 millimeter 3/4 inch socket. Notice we're tightening them evenly, but in a crossing pattern.That's going to compete our look at the U-bolt mounting kit for 3500 pound round trailer axles, part number APUBR-1.

Customer Satisfaction Score:

Customer Reviews

U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts - APUBR-1

Average Customer Rating:  4.8 out of 5 stars   (826 Customer Reviews)

Mount your round, 2-3/8" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included.


It is exactly as described. It seems solid. I also ordered the springs, and they appear to be solid as well. I look forward to continuing to do business with etrailer due to quality parts AND great customer service from the likes of Shawnee and the crew. Thank you!!!



It’s been a year and the trailer is as good as new. The leaf springs have held up well after many trips across the desert several miles of unpacked road and into town 80 miles one way to haul in materials cinder block, Portland cement, etc to finish building my house. Just bringing an empty load across these roads is abusive to any trailer, but many, many full loads later and the trailer is doing great! Thank YOU!


These did not fit my 3500 lb axle. It has been very difficult determining the correct size U-Bolts for my axle. It appears etrailer does not carry the size I need.

Etrailer Expert

Jenny N.


It is true that we do not carry all sizes of u-bolts. The best way to determine what you need to take a few measurements. First, you want to check to see if you have a round versus square axle. Second, using your old u bolt, measure the width on the inside of the u bolt [between the bolt arms]; this will match the width or diameter of the axle. Secondly measure the length of the bolt arm. This depends on the axle diameter and number of leaves on springs. The u-bolts must be long enough to clear the axle, spring seat, and springs. Last, you want to measure the diameter of the bolt arm. Please see the FAQs below, one for double eye trailer suspension and one for slipper spring suspension that will go into more detail.




I recently replaced my 1/2 ton truck with a 3/4 ton truck. In order to hook up to my existing fifth wheel camper, I had to raise my camper. To do this, my brother and I moved the axles from the top of the leaf springs and attached them under the springs. This kit made it very easy to do this. We torched off the old u bolts and used this set as a replacement. The quality of this kit was very good. Hard to get too excited about u bolts but I would purchase this again if I had to do it all over again.

I was able to gain about 5 1/2 inches by flipping the axles. Here is a before and after.


I replaced the rusted out U bolts on my 5x8 utility trailer with this kit, APUBR-1 from Redline. The kit fit great, no problems. Good quality parts. Great price. Would buy from etrailer again.


Everything worked great---All the correct parts ---the best place to buy parts.
very good service thanks to James. YEA

Janet L.


working great no problems!

Etrailer Expert

Mike L.


@JanetL We're glad to hear that!


The springs were a perfect match up. Easy installation with the exception of my existing rusted bolts Prompt service, exact replacements would not hesitate to use etrailer for any parts for my three trailers


This was used to replace original factory parts that were completely worn out. I am extremely happy with the parts I received. Everything worked like it was supposed too


This set of leaf springs was excellent choice for my 4’x8’ utility trailer, handles great.


The order was shipped like the day after it was placed. Everything seems to be high quality. There was even a color brochure that described the entire installation. Even though I was the distinguished honor graduate from my Alma Mater (Real Men Don't Need Instructions) I did read the pamphlet and found the instructions and tips to be very helpful.


It works as advertised….. what more do u need?


etrailer always has what I need in stock. And the parts are high quality. Plus their professionals always have sound advice and recommendations for me. They are a one stop shop! Than You etrailer!!


The kit was perfect to replace my original equipment on my 2007 trailer.


replaced my old axle and hubs with a heavy duty axle, U-bolts and new hubs. It has all held up well. I had to custom weld the axle carrier to fit my trailer, but everything fit well, and was a fairly easy installation. I now feel much more confident with a 3500 lb. axle and these heavy duty U bolts under my trailer.


I was shorted to you, Walts I called customer service. They immediately took care of it and shipped me out a new product. I’ve got to admit the quality of the product is great and the customer service is even better. Thank you E-trailer .


Easy installation and have worked just fine every since.


Last project built. Used etrailer for almost all parts, 7 pin wiring harnesses, junction block, tail lights, jacks, spring retainer bolts vent cover and so on. Love the leveling jacks. Friend wants one now so started another one. I will be getting all the parts from etrailer...


These axle u-bolt mounting kit worked great and did exactly what it was supposed to do. Install was easy and it contained the parts that I needed.


Purchased several axle and suspension/mounting parts from etrailer. Parts are always of good quality and work well. Shipping times are always reasonable. Plan to continue using them as a supplier for my trailer parts.


Fit perfectly for my trailer. All the components seem to be heavy duty.



Well, its been a year and I am still very impressed with the suspension parts I got from eTrailer. I have ran my car trailer from Michigan down to southern Ohio, Indiana, and Illinois. Had no issues what so ever. The trailer handled beautifully.


Very good, bolts right on.


Parts fit as advertised, very satisfied with purchase. I new nothing about replacing a trailer axle info on web site and support provided were excellent.
Definitely would recommend etrailer


I love the constant communication with Lori!!


It was so nice to work with new and proper fitting mounting bolts. Everything I needed to attach the axles was in the kit.


I am building my daughter and snl a kayak trailer so i ordered some new ubolts and plates. fit like a glove. Etrailer has what i9 want every time.

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