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  1. Fifth Wheel King Pin
  2. CURT
  3. Lippert 1621
  4. 21000 lbs GTW
  5. Absorbs Road Shock and Reduces Chucking
  6. Upgraded Pin Box
Curt Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs

Curt Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs

Item # LC328329
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Retail:$1,013.56
Our Price: $624.79
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Fifth Wheel King Pin
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Shipping Weight: 117 lbs
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This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 pin boxes. Call 800-298-1624 to order CURT fifth wheel king pin part number LC328329 or order online at etrailer.com. Free expert support on all CURT products. Guaranteed Lowest Price and Fastest Shipping for Curt Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs. Fifth Wheel King Pin reviews from real customers.
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  • Reviews (19)
  • Q & A (0)
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  • Why etrailer?

CURT Fifth Wheel King Pin - LC328329

  • Lippert 1621
  • 21000 lbs GTW
  • Absorbs Road Shock and Reduces Chucking
  • Upgraded Pin Box
  • CURT
  • Fixed Turret

This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 pin boxes.


Features:

  • Pivoting pin box replaces standard pin box on your 5th-wheel trailer to improve handling and limit strain on the truck and trailer
    • Minimizes chucking by allowing controlled movement of king pin within your hitch
  • Rubber compound built into the head absorbs road shock
    • Reduces wear and tear on trailer
  • Black powder coat provides rust resistance
  • Sturdy steel construction
  • King pin connects to any 5th-wheel trailer hitch
  • Bolt-on installation with no assembly required
  • Made in the USA


Specs:

  • Designed to replace Lippert 1621 5th-wheel pin box
  • Weight capacity: 21,000 lbs
  • 1-Year limited warranty


Diagram of measurements for the Curt Rota-Flex pin box

Notes:

  • Do not use the Curt Rota-Flex pin box with any type of gooseneck adapter.
  • The Curt Rota-Flex is not compatible with Curt E-Series or Q-Series 5th wheel hitches.

The Rota-Flex pin box has a pivoting head and built-in rubber compound that help to reduce checking and absorb road shock for a smoother ride as you tow your fifth-wheel trailer.


Pivoting Head Reduces Chucking

The Curt Rota-Flex pin box has a pivoting head to help reduce chucking

The pivoting head on the Rota-Flex allows for controlled back and forth movement of the king pin to reduce the uncomfortable jarring known as chucking. Unlike a rigid pin box that has little give at the point where the trailer and the hitch are connected, the Rota-Flex can pivot slightly to compensate for those times that your trailer suddenly pushes or pulls on your tow vehicle. Because the pin box head - not the king pin itself - is moving, the chucking that often occurs when the king pin jerks around inside the hitch is significantly reduced.


Rubber Compound Absorbs Road Shock

The Curt Rota-Flex pin box has a built-in rubber compound to help absorb road shock

A heavy-duty rubber compound is built into the head assembly of the Rota-Flex pin box. This rubber absorbs the bumps and vibrations, or road shock, experienced when towing a fifth-wheel trailer over rough roads. Standard pin boxes without any type of shock absorption transfer road shock to your trailer, resulting in potential damage to the trailer and an overall bumpy ride. The shock-absorbing rubber inside the Rota-Flex takes the beating so there's less wear and tear on your trailer or RV and you get a smoother ride.


Easy, Bolt-On Installation

The Rota-Flex is easy to install. Simply remove your existing Lippert 1621 pin box and install the Rota-Flex on your trailer or RV. The Rota-Flex uses the same bolts that held on your original pin box so no additional hardware is required. Plus, it comes out of the box ready to be put on your trailer, so no assembly is needed. Because the Rota-Flex is quite heavy, you should put it on an elevated surface or have a friend help you support its weight during installation.



328329 Curt Rotaflex Fifth Wheel Kingpin Box for Lippert 1621

Replaces 328329 Lippert Components (LCI) Rotaflex by Trail Air Fifth Wheel Kingpin Box for Lippert 1621






Customer Reviews

Curt Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs - LC328329

Average Customer Rating:  4.6 out of 5 stars   (19 Customer Reviews)

This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 pin boxes.

- LC328329
by:

Great product, unfortunately I was very displeased with how it was delivered. The product was unwrapped and had the potential to be scratched up and chipped.


Comments
Customer service will reach out to you. It is important to cover all bare metal with anti-corrosive paint to avoid rust. I have attached a help article regarding this.
-- Etrailer Expert Sierra K - 12/27/2021


- LC328329
by:

Great quality, great customer service - I’ll use E-trailer for everything I can now!



- LC328329
by:

I received the pin box in good condition. Preparing to install. Much anticipation to get rid of present air ride hitch which is woefully inadequate.



- LC328329
by:

Nice pin box



- LC328329
by:

Great service and fast shipping!! Great King pin . But wouldn’t fix my 5 wheel pin box.



- LC328329
by:

Switched from a ball. Glad I did. Very well pleased.



- LC328329
by:

Helps take the bumps out of our wonderful roads.



- LC328329
by:

Drove well



- LC328329
by:



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


It's a great pinbox. Really helped with chucking and compatible with my Demco sliding hitch. Also no issues with delivery, was helped by Pam and Jessie. They are awesome people to work with.



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Perfect replacement for my unit. The movement in the mount helps with the shock on the hitch itself. The unit is very strong and after a year I have had no problems. The instructions were spot on and shipping was very fast. I recommend this pin box as it is more economical than others I have seen but really helps on the bump and pull with a solid hitch



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


The pin box made the 5th wheel handle better, with less chucking and very stable.



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Definitely dampened the chucking and my wife is much happier with the ride. Also it seems to be much quieter. Noticed at the camper show many units come with the Roto flex from the factory.



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Got it on and ready to try. It fit nicely. Did it myself in about an hour . Nothing left of the box it was in but other than a couple of scratches the pin box itself was in good condition



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


The hitch arrived poorly packaged in a cardboard box. The hitch is very heavy. It was scratched and required repainting. The hitch itself looks well made and strong.



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


I installed this by myself (it is heavy!) by putting it in the bed of my pickup & strapping it to a floor jack but not a job I’d recommend doing it by yourself. I already have airbags on the rear axle of my pickup is why I chose this king pin . Only a 200 mile trip and the bucking on the 5th wheel was gone. But the real test will be on a rough highway...



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Have not installed yet, paint has been scraped off in several locations especially on top and on the rounded corners from shipping. Will have to do some touch up painting. Excited to get installed and pull trailer next weekend



- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Great product, Installed and what difference the ride. Thanks SJ McDonnell


Comments
Great hauls good thanks
Sean M - 06/21/2021


- LC176440
by:

Review from a similar Trailair Rota-Flex in Fifth Wheel King Pin


Works great eliminated the jaring. Also shorter so I can make a hard turn without touching the sides of my box


21
21

Ask the Experts about this CURT Fifth Wheel King Pin



  • Troubleshooting Roto-Flex Pin Box Screeching/Scratching Noise
    The noise you described would be from the pivot point of the Rota-Flex. I spoke with my contact at Lippert and he said that typically when the noise you described is heard it is because there is a gooseneck adapter on the pin box which isn't recommended. To lube the pivot point my contact said to take the bolts out of the lower piece, pull the pin out, and then put lube in where the pin rotates.
    view full answer...
  • How To Fix a Misaligned Pad On the Trailair Rota-Flex 5th Wheel Pin Box
    Yes, the rubber cushion inside the Trailair Rota-Flex 5th Wheel Pin Box like part # LC328329 is essential to its functionality so if this is out of place or misaligned then that is certainly a cause for concern. That said, this is actually covered under warranty as it is a known issue. If you have proof of purchase then Lippert with send you an entire replacement pin box but if you do not have proof of purchase then you would need to replace the pin box on your own. If that is the case...
    view full answer...
    Image 1 for
  • Does Trailair Rota-Flex 5th Wheel Pin Box Have Bolster Plate
    I spoke with my contact at Lippert regarding the Trailair Rota-Flex 5th Wheel Pin Box # LC328329 and he said that the heavy-duty rubber compound that's built into the head assembly serves as the bolster plate. It will do a great job of absorbing bumps and road shock as well as adding support to the connection. I have also attached an image pointing out this component on the pin box.
    view full answer...
    Image 1 for
  • Is the Rubber for the Trailair Rota-Flex Pin Box Replaceable?
    The Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs # LC328329 does not have that rubber compound as a replaceable part option from the manufacturer. I called to confirm that was the case and they said the rubber compound is built into the head. That rubber compound is designed to reduce wear and tear on the trailer by reducing road shock. It is extremely durable and I've never heard of anyone needing it replaced but older models had a different jounce style bumper that...
    view full answer...
    Image 1 for
  • Does Trailair Pin Box with 21k Trailer Weight Capacity have Stated Pin Weight Capacity
    The Trailair Rota-Flexes like the part # LC328329 that you referenced do not have stated pin weight capacities so as long as the trailer's overall weight is less than 21k it would be safe to use. Typically pin weight is 20 percent of the total trailer weight.
    view full answer...
  • Can Gooseneck Adapter Be Used With Trailair Rota-Flex 5th Wheel Pin Box?
    A gooseneck adapter cannot be used with the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs # LC328329 because of the excess play and movement that would be present at the connection point. You would instead need to swap out your setup for a gooseneck setup.
    view full answer...
  • Replacement Pin Box For Fifth Wheel Trailer With Lippert 1621 Pin Box
    I called my contact at Lippert and they told me the 119115 number you referenced is actually the Lippert 1621 pin box. We do not offer a Flex Air pin box that has a weight capacity of 21,000-lbs. The highest capacity Flex Air unit we offer is part # LC328492. it has a capacity of 18,000-lbs. We do offer the Rota-Flex pin box, part # LC328329, that can replace your 1621, and has a 21,000-lb capacity. This system has a pivoting head and built-in rubber compound that absorbs road shock...
    view full answer...
  • Will The Trailair Flex Air 5th Wheel 18000 lb Capacity Pin Box Fit My 2017 Dutchmen Voltage 3990?
    I can confirm that the Trailair Flex Air 5th Wheel Pin Box - Lippert 1621 - 18,000 lbs, # LC328492, is a fit for your trailer's pin box. I highly recommend this pin box because of the Flex Air System. The air bag absorbs road shock and the scissor-like motion allows the pin box to compress, compensating for bounce and chucking. The shock absorber ensures that the pin box rebounds and keeps the air bag from breaking down. There is a rubber compound built intot he head that helps absorb...
    view full answer...
  • Replacement Fifth Wheel Pin Box for Lippert 1621 to Improve Quality of Ride
    We do not carry MORryde pin boxes. We do have the Trailair Rota-Flex # LC328329 which uses a rubber compound to decrease road shock and improve the ride of your trailer. Also, the Trailair Air Ride # LC158778 has an air bag and built-in shock to absorb road shock and minimize chucking. Both products come fully assembled, are rated at 21,000 pounds, and will bolt-on to replace your Lippert 1621 pin box.
    view full answer...
  • What are Available Capacities for Lippert Rota Flex Pin Boxes to Replace 1621 Pin Box
    For Trailair Rota-Flex pin boxes that fit as a replacement for a Lippert 1621 we have the 21k part # LC328329 and we have the # LC328330 which it sounds like you have. I can assure they aren't both really rated for 21k and the only difference is a part number and a few stickers. While the differences are hard to see by just looking at pictures of the two the 21k version is reinforced in areas you can't see and does have a higher capacity. If you are going to be over the 18k capacity of...
    view full answer...
  • Dimensions of the Rota-Flex 5th Wheel Pin Box # 328330
    The Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330 does require capture plates for the Demco Hijacker autoslide that is similar to the Pull Rite Autoslide you have. The measurement from the front of the plate to the king pin is 4-1/2 inches. The overall plate is 11.387 inches by 12.655 inches.
    view full answer...
    Image 1 for
  • Replacement Pin Box Recommendation for 2009 Cardinal 34QRL with Trailair 181445
    I sent this info to Trailair to help identify what you have and they informed me that you have a Rota Flex pin box that was designed to fit as a Lippert 1621 replacement. Replacement parts are not available for this style of pin box since it's now discontinued but we do have the upgraded version of what you have with the Trailair Flex Air part # LC328492. This has a similar front to back cushioning as your Rota Flex but also has a vertical cushioning setup with an air bag and shock which...
    view full answer...
  • Will Trailair Rota-Flex 5th Wheel Pin Box for Lippert 1621 Reduce Chucking
    The Trailair Rota-Flex 5th Wheel Pin Box # LC328329 that will replace your Lippert 1621 has a rubber compound in the head, so it will have an affect on your ride, helping to reduce the chucking you are experiencing. That said, the rubber compound does not have as much give as an air bag, so you will still feel it, just not as drastically. So if you looking to severely limit the chucking and get the most comfortable ride possible the best option to replace your Lippert 1621 pin box is...
    view full answer...
  • How Tall Is The Trailair Rota-Flex 5th Wheel Pin Box
    The Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330 is 33 inches long, 12 inches wide and 7 inches from the bottom of the skid plate to the top of the farthest bolt hole.
    view full answer...
    Image 1 for
  • Which Trailair Rota-Flex Pin Box Compatible with Lippert 1621 Pin Box
    I have a solution for you, but the Trailair Rota-Flex # LC176440 pin box is designed to replace 5th wheel trailers with a Lippert 1116 pin box and not the 1621 pin box. Instead, you'll want to use either the # LC328330 (trailer with GVWR of less than 18000-lbs) or the # LC328329 (trailer of GVWR less than 21000-lbs). The Trailair Rotaflex is a great solution to help reduce the bouncing and jarring that car be experienced with an uncushioned pin box and will be a great upgrade for your towing...
    view full answer...
  • Is Trailair Rota-Flex Pin Box Available in 12-3/8 Inches Wide?
    The Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD -18,000 lbs # LC328330 and the 21,000 lbs # LC328329 are 12-1/2 inches wide. The sizes of pin boxes for width are simply 12 inches or 12-1/2 inches so you would definitely want the 12-1/2 inch pin box. You will want to check your current pin box number which should be on a sticker on the actual box itself. If not there, you will want to measure your mounting bolts to ensure the correct fit. I've attached an article...
    view full answer...
  • Rota-Flex Pin Box Replacement For Lippert 1621HD
    There is a Rota-Flex pin box that will replace your 1621HD pin box, but I checked with the manufacturer, and the part number you mentioned will not fit as a replacement. Instead, the correct Rota-Flex for your 1621HD is the following: - Trailair Rota-Flex 5th Wheel Pin Box # LC328330 The # LC328330 does have an 18,000 lb capacity, so if you were looking for a replacement cushioned pin box with a 21,000 lb capacity like the one in your question, you'd need to go with a different option,...
    view full answer...
  • Solution for Hitch Noise of Roto-Flex Pin Box Trailer Towed with Curt Q20 Hitch
    The thing that causes the noise you are experiencing is actually the hitch you have and not the Roto Flex. The biggest factor in how much noise you'll experience when towing a fifth wheel trailer is the hitch itself since it has moving parts and it's responsible for grabbing onto the trailer. The Q20 hitch you have is not known to be super quiet so I'm not totally surprised you are having issues with noise. If you wanted to quiet down your towing setup a quieter hitch would be the best...
    view full answer...
  • Correct Capture Plate Needed to Use PullRite 4100 SuperGlide with Rota-Flex 5th Wheel Pin Box
    According to PullRite you will need to measure from the front edge of your king pin to the leading edge of the king pin plate to verify which capture plate to use with your Rota-Flex 5th Wheel Pin Box, like part # LC328329. If that measures 5-3/8" then you need capture plate 331707 but if it is just 5" then you need capture plate 331760. You can acquire either of these from PullRite.
    view full answer...
    Image 1 for
  • Is The Reese Goose Box Item # RP94720 Compatible With A 2021 Keystone Montana 376FL
    Great question! Yes, the Keystone Montana with a Lippert Components fifth wheel pin box like Item # LC328329 are very common size pin boxes which it makes the trailer easily adaptable to a gooseneck. I recommend the Reese Goose Box 5th-Wheel-to-Gooseneck Air Ride Coupler Adapter Item # RP94720. It replaces the Lippert 1621, 1621HD, and 0719 fifth wheel pin boxes. This hitch, having a 20,000 lb towing capacity gives you plenty cushion for your Keystone, which comes in at a total weight...
    view full answer...
  • Why Can't Furniture Switch # 37213925 be Used with Slide Out
    It's an amperage problem. The # 37213925 can only support 40 amps peak and 20 continuous whereas the switches for slide outs like the part # 37212075 can handle 40 amps continuous.
    view full answer...
  • Replacing Rota Flex Pin Box On 2019 Grand Design Solitude Fifth Wheel.
    Great question and information. Based on your information I recommend the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330. Since your trailer is at 16,800 GVWR you really do not need to go up to 21,000 unless you just want to. The 18k capacity of this pin box will be enough. If you do want the larger capacity you can get it here. Curt Rota-Flex 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs Item # LC328329. From the center of the king pin to the center...
    view full answer...
  • Replacing Lippert Rota-Flex with Reese Goose Box on 2018 Grand Design Solitude
    To replace your existing Rota-Flex 5th wheel pin box with the Reese Goose Box 5th-Wheel-to-Gooseneck Air Ride Coupler Adapter # RP94720, you'll need to confirm its model number and weight rating. This information is typically displayed on a sticker or plate on the pin box itself. Lippert makes three models of the Rota-Flex, so the weight rating on the label is enough to identify which of these three you have: -Model 1621/1621HD Trailair Rota-Flex 5th Wheel Pin Box 18,000 lbs # LC328330 -Model...
    view full answer...
  • Are 5th Wheel Trailer Pin Boxes Compatible with Gooseneck Adapters
    It really depends on the pin box and the type of adapter. In general cushioned pin boxes and pin boxes with movement are not recommended for use with adapters. Many 5th wheel trailer frame manufacturers do not allow the use of most adapters with the exception being Lippert provided that the adapter is a Reese Goose Box. So for example if your stock pin box is a Lippert 1621 you could use Reese Goose Box # RP94720 which is rated for 20,000 pounds or # RP94716 for 16,000 pounds. The use...
    view full answer...


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Info for this part was:

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