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Sidewinder Rotating Turret Premium Pin Box Coupler - ST400

Sidewinder Rotating Turret Premium Pin Box Coupler - ST400

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ST400 - Sidewinder Parts Reese Accessories and Parts
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This Sidewinder rotating turret premium pin box coupler is designed to work with the Sidewinder standard or super duty arm. 1-800-940-8924 to order Reese accessories and parts part number ST400 or order online at Free expert support on all Reese products. Guaranteed Lowest Price and Fastest Shipping for Sidewinder Rotating Turret Premium Pin Box Coupler - ST400. Accessories and Parts reviews from real customers.
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  • Reviews (5)
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  • Videos (1)
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  • Why etrailer?

Reese Accessories and Parts

  • Fifth Wheel King Pin
  • Sidewinder Parts
  • Leland Pin Box
  • Reese

This Sidewinder rotating turret premium pin box coupler is designed to work with the Sidewinder standard or super duty arm.


  • Rotating turret style premium pin box coupler
  • Designed to work with the Sidewinder's standard or super duty arm
  • Fits OEM pin boxes
    • Leland: 7910, 7920, and 7921
    • Dexter: 221-00374
  • Made in the USA

ST400 Sidewinder Rotating Turret Premium Pin Box Coupler - ST400

Item # ST400

California residents: click here

Video of Sidewinder Rotating Turret Premium Pin Box Coupler - ST400

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

Video Transcript for Reese Fifth Wheel King Pin ST400 Review

Speaker 1: Today we're going to take a look at the Reese sidewinder rotating turret premium pin box coupler. Now, this rotating turret style premium pin box coupler will replace the factory pin box on your Fifth Wheel. This part is designed to install onto the Reese Sidewinder Standard or Super Duty arm and allows the sidewinder rotate 90 degrees.The Reese sidewinder is designed specifically for short bed trucks. A nimble, quick design will automatically eliminate turning and clearance headaches and allows you to make up to 90 degree plus turns without exiting the truck. This part will include just the turret, the rotating turret with the wear bushing, the installation hardware and the wear disc to allow you to install this onto the sidewinder. It is designed to fit standard OEM pin boxes like the Leland 7910 and it fits extended OEM pin boxes like the Leland 7920 and 7921.

This part is made in the USA. The last thing I want to do is just give you the measurements of the mounting holes here on the side. Center to center is going to measure right at 7". That should do it for the review on the Reese sidewinder rotating turret premium pin box coupler.

Customer Reviews

Sidewinder Rotating Turret Premium Pin Box Coupler - ST400 - ST400

Average Customer Rating:  4.6 out of 5 stars   (5 Customer Reviews)

This Sidewinder rotating turret premium pin box coupler is designed to work with the Sidewinder standard or super duty arm.

- ST400

Awesome coupler. Takes a little bit of lithium grease to install and a 2x4 to persuade it into the pinbox. Molly at etrailer has provided all the technical details needed to get this turret on the fifth wheel. Ive had it on for about a year and works beautifully.

Still working like it should
Eli - 06/20/2022

- ST400

Fit as expected.... Very quick delivery.... Although they were no directions how to assemble onto the sidewinder arm or any information on torque specs a simple search took care of that.... I do not believe that was a etrailer issue make it was a manufacturer issue as far as no directions...

- ST400

Great service and fast shipping.

- ST400

First one delivered did not fit they shipped another that worked well.

- ST400


See what our Experts say about this Reese Accessories and Parts

  • Sidewinder Rotating Turret # ST400 Making Popping Sound When Turning
    I contacted our representative at Cequent about the Sidewinder Rotating Turret, part # ST400. He recommended you begin by checking the torque on the top bolts of the turret. You will want to make sure that these bolts are not over torqued, which could be causing the problems you are having. The other thing, since the unit is pointing upward slightly, is to adjust the height of the 5th wheel hitch. But when doing this, you will want to make sure there is at least 6 inches of clearance from...
    view full answer...
  • Replacement Turret For A Leland 7910
    There aren't adapters that will make up the two inch difference so what you can do is replace the turret of your current sidewinder with the correct fitting turret to replace a Leland 7910, which is the Sidewinder Rotating Turret Premium Pin Box Coupler # ST400.
    view full answer...
  • Dimensions of Pin Box Coupler # ST400 and What Pin Boxes it Will Fit
    I certainly can. I went out to the warehouse and pulled the mounting part, # ST400, and did the measurements myself. The Sidewinder Rotating Turret Premium Pin Box Coupler, # ST400, is made to fit pin boxes: Leland 7910, 7920, and 7921; 5AB-E7920; Demco-GR19LND7920; Trail Air-L08; Mor RPB72-7920. If looking at the box from the side, it is 13-1/2 inches long at the base, and 9-3/4 inches long at the shortest point (nearer the top). It is 8-1/8 inches tall at the tallest point. It is 5-3/8...
    view full answer...
  • Sidewinder Rotating Turret Replacement Pin Box for Leland 7921
    The Sidewinder Rotating Turret Premium Pin Box Coupler - ST400 # ST400 is a fit for the Leland 7921 pin box meaning it will bolt onto your trailer to replace it that pin box. The full rotating pin box to replace your current Leland 7921 is the 5th Airborne Premium 5th Wheel Air Ride King Pin w/ Sidewinder and Turret - 16,000 lbs # ST400-5AS16K.
    view full answer...
  • Sidewinder Fifth Wheel King Pin for a Sliding Fifth Wheel Hitch
    Yes, you can use a Sidewinder Fifth Wheel King Pin ST400-SW01 with a sliding fifth wheel hitch. The Sidewinder eliminates the need for a slider, but they can still be used together. In this situation you cannot use the slider in the rearward position. It would center weight behind the rear axle and could lift the front end of the truck.
    view full answer...
  • Recommendation for Applying Grease to Reese Sidewinder Turret
    During initial installation, I recommend applying a good amount white lithium grease like # L11354 to the inner tube of the Sidewinder Turret # ST400 referenced in your question. This will help in fitting the components together for the first time. Along with the turret itself, you will want to apply grease to the surface on both sides of the wedge, the area where the jaw passes under the wedge, and around the king pin and skid plate. Reese also recommends that at least once per season...
    view full answer...
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  • Will the Reese RP77FR Fit a Leland 7921 Pin Box?
    The Reese Sidewinder # RP77FR is designed to fit Lippert pin boxes 1716, 1116, and 0115. As you have a Leland 7921, this will not fit your set up, unfortunately. That being said, if you do not want to go with the Reese 5th Airborne # ST400-5AS16K, I do still have an option available for you. The Reese Turret # ST400 is designed specifically for the Leland 7910, 7920, and 7921 pin boxes. Though the arm portion of # RP77FR is not sold separately, this part can be added to get everything...
    view full answer...
  • Will Obsolete Sidewinder Turret ST600 Fit the New Sidewinder Arm # SW16K
    None of the available Sidewinder turrets are a confirmed fit for the Leland 7930 pin box. If the ST600 is and you can find one then grab it while you can! There are only models for the 7910, 7920, and 7921 pin boxes. They use the ST400 turret # ST400. You can take some measurements of your pin box, see link to the right, to determine if the measurements are the same as the above mentioned pin boxes and if so then you could use an ST400 set up.
    view full answer...
  • Replacement Rotating Turret for a 5th Airborne Sidewinder from Lippert Pin Box to Leland Pin Box
    You will need the Sidewinder Rotating Turret Premium Pin Box Coupler, item # ST400, to switch the Lippert rotating turret to a Leland rotating turret on your 5th Airborne Air-Ride Sidewinder. You can review the conversion table (see link) to see the parts for both Leland and Lippert pin boxes.
    view full answer...
  • How Tight do you tighten the Bolts that Connect the Turret to the Pin Box on the Sidewinder?
    The bolts that hold the turret to the Pinbox on the Reese Sidewinder part # ST400-SW19K should be set according to the instructions initially to 150 ft/lb using a crossing pattern 2-3 times then backed off and tightened down to 45 ft/lb. At that point it is set per the factory instructions. These are linked below if you need to check them out.
    view full answer...
  • Sidewinder Rotating Turret Premium Pin Box Coupler for Leland 7920
    The Reese SW16K is not available but we do have the Sidewinder Rotating Turret Premium Pin Box Coupler, # ST400 and the MORryde pin box # MR52VR for 14-18K application.
    view full answer...
  • Will Sidewinder ST400 Turret Fit SW16K Pin Box
    The SW16K is just the arm of a Sidewinder so if you wanted to fit it to the turret part # ST400 you certainly could.
    view full answer...
  • What Does a Sidewinder Replacement Pin Box Come With
    The Sidewinder replacement pin box # ST400-5AS16K includes the arm (to which the king in is attached), turret, and universal wedge. Hardware is not included because you can reuse the hardware from the old pin box. Other than that it is ready to bolt onto a trailer that has a Leland 7910, 7920 or 7921 pin box.
    view full answer...
  • Are Leland 7910 and 7920 Pin Boxes the Same Except for the Length
    The Leland 7910 and 7920 pin boxes are very similar with the difference being the length of each. The 7920 is longer, like you said, measuring 21 inches from the first row of bolt holes to the center of the king pin whereas the 7910 is 9 inches. I have included a link to the pin box options for the Leland pin boxes.
    view full answer...
  • Can Sidewinder Pin Boxes have Slight Side to Side Movement When Towing 5th Wheel Trailer
    There is a lot of weight, a lot of force involved with 5th wheel towing. You may be seeing the metal flexing. Or it could be that the wedge is not all the way into position allowing for slight movement at the wedge which looks like more movement further back. It is not anything out of the ordinary. If you end up getting a Sidewinder I recommend making sure the wedge is in its proper position before torqueing it down to spec.
    view full answer...
  • Measuring the Pin Box on a 2006 Fleetwood 5th Wheel Trailer to Find a Replacement Pin Box
    There are a couple of things you can do to identify the pin box on your trailer. First, you can call the trailer manufacturer with the trailer serial number and they may be able to tell you the make and model of the pn box. If they cannot help you, there are some measurements you can take on the pin box and I can use those to determine if there is a 5th Airborne Pin Box that is compatible. I have included a picture that shows the measurements needed.
    view full answer...
    Image 1 for
  • Can a Truck with a 5-1/2 foot Bed Tow a Gooseneck or Fifth Wheel Trailer with Turning Clearance
    Honestly no, if it was a fifth wheel hitch you could replace the pin box with a Sidewinder like the # ST400-5AS16K that you referenced. But there are no products available for gooseneck trailers that would allow a trailer as wide as what you are considering to have enough turning clearance with a bed as short as your truck's.
    view full answer...
  • Air Spring Pressure Setting and Adjustment of the 5th Airborne with Sidewinder Air-Ride Coupler
    A good starting point for pressure setting is 80-100 psi (Do Not Exceed 120 psi). Air should be added until the skid plate is level. If the ride is too soft, add more pressure. If the ride is harsh, remove pressure. If the pressure adjustment cannot maintain a satisfactory ride, reposition the air spring. When repositioning the air spring if the pin weight is heavy move it rearward and if the pin weight is light move the air spring forward. Directions for air pressure and moving the air...
    view full answer...
  • Will 5th Airborne Sidewinder 5th Wheel Air-Ride Coupler # ST400-5AS16K Fit 2009 Ram 3500 MegaCab
    The 5th Airborne Sidewinder 5th Wheel Air-Ride Coupler # ST400-5AS16K is intended for use with 5th wheel hitches on short-bed trucks. Replacement pin boxes need to be matched based on the original pin box on the 5th wheel trailer in order to ensure bolt-on compatibility. This particular 19K pin box is a direct replacement for Youngs Welding standard and extended pin boxes, but will not fit in place of their tube style coupler. You will want to verify which pin box is installed on your...
    view full answer...
  • Sidewinder Replacement Pin Box for a 5th Wheel Trailer with a Leland 7910 Pin Box
    There are a few options for your Leland 7910 pin box. You will want to make sure you get one that has a high enough capacity for the trailer. If you are interested in an air ride coupler/Sidewinder combo to improve ride quality and reducing chucking and vertical shock we have 2 options. We have # ST400-5AS16K rated for 16K. When using a Sidewinder you will need to keep the 5th wheel hitch locked in the towing position. Do not slide it back when using a Sidewinder because it produces...
    view full answer...
  • How Far Back Does a Sidewinder Pin Box Move a 5th Wheel Trailer Pivot Point
    On all of the Sidewinders, including # ST400-5AS16K, the pivot point is moved back 22 inches. The Sidewinders will only fit certain trailer pin boxes. This one fits Leland 7910, 7920 and 7921 pin boxes. The pin box manufacturer and model number should be on a sticker or plate on the pin box itself. Then you can use the chart in our Sidewinder help article, linked for you, to determine if there is one available that will fit.
    view full answer...
  • Would a Sidewinder Allow a 2014 GMC Sierra with a 5 ft 8 in Bed Tow a Fifth Wheel Trailer
    Yes it will, Sidewinders like # ST400-5AS16K were specifically designed to work in very short truck beds like the 5 foot 8 inch bed in your 2014 GMC Sierra 1500. In order to pick out the correct Sidewinder you will need to know what pin box you have on your trailer. This should be on a sticker or plate on the pin box itself. For example, the # ST400-5AS16K is designed to fit the Leland 7910, 7920 and 7921 pin boxes. If the pin box of your trailer is one of those then this would be the...
    view full answer...
  • Using Sidewinder to Make Room for Carrying Motorcycle Between Fifth Wheel and Truck
    I have not heard of anybody carrying a motorcycle in the way you described. There would be a few things to consider. The fifth wheel hitch needs be placed on the bed so that the king pin is no farther rearward than the centerline of the rear ruck axle. If the hitch is any farther rearward than that, the trailer's pin weight will make the front end of the truck too light, thus affecting the steering response and front braking performance. You will also need to make sure your flat bed has...
    view full answer...
  • Required Air Pressure for 5th Airborne Premium Fifth Wheel Air-Ride Coupler
    I spoke with my contact at Fth Airborne and he suggested you adjust the air pressure upward to 120 psi. Increasing the air pressure will help level the skid plate. However, do not exceed 120 psi. Please note that when setting air pressure your vehicle and trailer need to be on level ground. He also said if you are close to or a little shy of the line you will still be able to operate your rig effectively. I have linked you to the install/user manual for part # ST400-5AS16K.
    view full answer...

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Info for this part was:

Employee Jeff D
Installed by:
Jeff D
Employee Reno H
Expert Research:
Reno H
Employee Wilson B
Updated by:
Wilson B
Employee Alexander C
Updated by:
Alexander C
Employee Hannah L
Updated by:
Hannah L

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