Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs

Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs

Item # LC158778

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Fifth Wheel King Pin

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Shipping Weight: 184 lbs

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LC158778 - Lippert Lippert Components Fifth Wheel King Pin
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Enjoy smooth, stable towing with your fifth-wheel trailer by replacing your ordinary pin box with this air-ride-equipped model. An internal air bag and built-in strut absorb road shock so that you won't feel it. Replaces Lippert 1621 pin boxes. Call 800-298-8924 to order Lippert Components fifth wheel king pin part number LC158778 or order online at Free expert support on all Lippert Components products. Guaranteed Lowest Price and Fastest Shipping for Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs. Fifth Wheel King Pin reviews from real customers.
  • All Info
  • Reviews (15)
  • Q & A (219)
  • Videos (3)
  • Photos
  • Why etrailer?

Lippert Components Fifth Wheel King Pin - LC158778

  • 1621HD
  • Lippert
  • Reduces Bounce and Jarring
  • Lippert Components
  • 21000 lbs GTW
  • Pin Box Upgrade
  • Cushioned
  • Fixed Turret

Enjoy smooth, stable towing with your fifth-wheel trailer by replacing your ordinary pin box with this air-ride-equipped model. An internal air bag and built-in strut absorb road shock so that you won't feel it. Replaces Lippert 1621 pin boxes.


  • Air ride pin box replaces standard pin box on your 5th-wheel trailer to cushion your ride, improve handling, and limit strain on truck and trailer
    • Minimizes chucking
    • Eliminates bounce and jarring
  • Internal air bag absorbs road shock
    • Scissor-like motion allows pin box to compress, compensating for jarring and bounce
    • Built-in shock ensures that pin box rebounds - keeps air bag from breaking down
  • 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


  • Designed to replace Lippert 1621 and 1621HD long-jaw 5th-wheel pin boxes
  • Weight capacity: 21,000 lbs
  • Length (from outside edge of mounting plate to center of king pin): 28-11/16"
  • 1-Year limited warranty

Note: Do not use the Trailair air ride pin box with any type of gooseneck adapter.

Getting there is half the fun, right? Not if you're being bumped, jerked, jammed, and pushed around from the chucking and road shock that occurs as you tow your fifth-wheel trailer or RV. And imagine the costly wear and tear on your trailer as it endures that rocky ride.

Put the fun back into your trip and ease the stress on your trailer by replacing your factory pin box with the Trailair air ride pin box. The internal air bag and built-in shock work together to cushion your ride, improve handling, and limit strain on both your truck and your trailer.

Air Bag Absorbs Road Shock

Lippert Trailair air ride pin box air bag and shock

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. But the Trailair air ride pin box absorbs shock and cushions your ride as you pull your fifth-wheel trailer. When you encounter uneven terrain on your trip or hit a pothole on the highway, the Trailair pin box compresses vertically, similar to how a pair of scissor blades closes in on each other. This compression transfers the road shock and vibrations to the internal air bag, saving your fifth-wheel hitch, trailer, or tow vehicle frame from enduring a rocky ride.

A built-in strut, or shock, controls the Trailair's compression so that the internal air bag doesn't burst. The strut also causes the pin box to appropriately rebound without any bounce, and positions it to be ready for the next bump in the road.

Simple Setup and Installation

First, simply remove your existing Lippert 1621 or 1621HD pin box from your trailer. The Trailair uses the same bolts that held on your original pin box so no additional hardware is required for installation. Plus, the Trailair pin box comes out of the box ready to be put on your trailer, so no assembly is needed. Because the Trailair is quite heavy, you should put it on an elevated surface or have a friend help you support its weight during installation.

Lippert Trailair air ride pin box air intake valve and inflation indicator

The internal air bag should be inflated after the pin box has been mounted on your trailer. Using the air intake valve, inflate the air bag until the outer cylinder of the shock rises high enough to fully expose the yellow inflation indicator sticker.

158778 Lippert Components (LCI) Air Ride by Trail Air Fifth Wheel Kingpin Box for Long Jaw Lippert 1621 and 1621HD

Same as 35-946203 Ultra-Fab Air Ride Trail Air Kingpin Box

Replaces 171200

Video of Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs

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

Video Transcript for Lippert Components Fifth Wheel King Pin - Pin Box Upgrade - LC158778 Review

Today, we're going to review part number LC158778. This is the Lippert Trailair air ride fifth wheel pin box. It is designed for the Lippert 1621 pin boxes. Has a 21,000 pound weight capacity. Now, this air ride pin box will replace the standard pin box on your fifth wheel trailer. This is designed to cushion your ride, improve your handling, and even limit the strain that's put on your truck and trailer.

It does minimize chucking, and it will also eliminate the bounce and jarring, which is also known as the porpoising. Basically, when you get that movement when you hook up your trailer to your truck, and you get that up and down porpoising movement, that would be the bounce and the jarring. Has an internal airbag right here on the inside, which will absorb the road shock. If you notice this bottom plate, there's a pivot point right there, actually gives you a scissor like motion, and this allows the pin box to compress, which compensates for the jarring and the bouncing. The very end right here has a built-in shock, and this shock will insure that this pin box will rebound, keeps the airbag from breaking down or any damage to it. Now, the internal airbag right here on the inside after this pin box has been mounted onto your trailer, you want to inflate that airbag.

Basically, the air valve right here at the top is where you inflate it. What you'll do is, to give you an idea of how much to put in it when you're inflating it, is just watch the shock out here, because you want this outer cylinder of the shock to rise enough to fully expose this yellow inflation indicator sticker right on the front here. On the sticker it says, inflate to this point. There's two arrows pointing up, so you just want it to go above that top point where the arrows are pointing. That'll give you a good starting point of how much air to put in the airbag. It does have a black power coat finish to help provide rust resistance.

It is a sturdy steel construction. Now, the king pin right here on the bottom will connect to any fifth wheel trailer hitch. It is a bolt on installation. You can see the bolt pattern right here. There's no assembly required.

It is made in the U.S.A. The specs on this again, it's designed to replace the Lippert 1621 long jaw fifth wheel pin box, has a weight capacity of 21,000 ponds. Now, when you do replace your pin box with another pin box, you want to make sure the pin box you get has the same bolt pattern right here, so it's able to bolt to your trailer. Now, this one again is designed to fit the Lippert 1621. A couple of measurements I want to give you. The horizontal measurement, the distance between the front row of holes to the rear row of holes, center to center, that measurement's going to be right at seven and three-quarters. The vertical distance from the center of one hole to the center of the hole right above it, it's right at two inches. The bolt hole diameter is five-eighths inch diameter. Another critical measurement is going to be the overall width of this pin box. What I'm going to try to do is rotate this, so we can measure that. Show you where to measure, that is. It's going to be from the outer edge to the outer edge. So, we got it turned, and put a ruler on the outer edge. You can see right at twelve inches for the overall width on the pin box. A couple other measurements I want to give you. Let me rotate it around here. I want to give you the measurements from the center of the king pin to the front row of those bolts, and then the center of the king pin. There we go. We're going to do from, I've got a mark put on here, which is the center of the king pin. We're going to go to the center of the front row of bolts, and then the center of the king pin to the rear row of bolts. Get a long ruler here. Once we get that lined up, you can see from that center king pin to the front row is going to be nineteen and a half. To the center to the rear is going to be right at twenty-seven and three-eighths inches. One last note to mention, this Trailair air ride pin box cannot be used with any type of loose neck adapter. That should do it for the review of part number LC158778. This is the Lippert Trailair air ride fifth wheel pin box, designed for the Lippert 1621 pin boxes, and has a 21,000 pond weight capacity. .

Customer Reviews

Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs - LC158778

Average Customer Rating:  4.9 out of 5 stars   (15 Customer Reviews)

Enjoy smooth, stable towing with your fifth-wheel trailer by replacing your ordinary pin box with this air-ride-equipped model. An internal air bag and built-in strut absorb road shock so that you won't feel it. Replaces Lippert 1621 pin boxes.

- LC158778

I am pleased with the Trailair kingpin hitch. Just waiting for warmer weather to go camping. 614451

- LC158778

Great product to tame the 5er bucking down the highway on those concrete seams. Ride is much smoother and I'm sure it is reducing the wear going down the highway on both the trailer and the truck. 526032

- LC158778

Unbelievable difference from the standard king pin hitch! Made I-40 and I-70 a pleasure instead of a workout. Will definitely purchase again on the next trailer. 484377

- LC158778

Have the Lippert Components Trailair fifth wheel king pin installed on our 40 foot Big Country has made the difference in pulling the trailer down the road. I would recommend the King Pin if pulling a fifth wheel trailer. Now we don't even know it behind us. Great Product. 468371

- LC158778

Works great but doesn't hold air for more then a couple days. 539734


Your trailair should not be losing air that quickly. Changes in temperature can affect the pressure in the air bag just like it does with vehicle tires but only by a few psi. It sounds like you need a new tank valve for it part # LC156740
Replacement Pin Box Tank Valve for Lippert or UltraFab TrailAir Pin Boxes
. I have attached a link to the replacement valve.

-- Heather A - 07/11/2018


- LC158778

Very satisfied with the TrailAir. I love it so much that I went ahead and put air bags on my truck to also help. I'm looking forward to Easter for our first camping trip of 2018. Thanks for checking in. 478248

- LC158778

I love this AirRide by Trail-air. It provides an incredibly smooth ride on the road. You can adjust the amount of air for your ride, the Schrader valve is right on top of the unit and easy to access. My Trail air installed easily on my Forest River Sandpiper 372LOK mid bunk, especially with help from my Dad. This Trailair solved a big problem for me. I needed an extra couple of inches space between my 2018 Ford Super Duty DRW and the coach. My truck came with the Ford factory-installed Reese 27K hitch and I needed more clearance to allow the tailgate to drop without touching the coach. The kingpin on the Trailair sits at least 2” forward of the factory kingpin and provided that desperately needed space. It really makes for smooth and quiet ride ! etrailer folks were very helpful. The first unit was damaged by the freight company and when I notified them, etrailer sent another unit quickly. I will buy from etrailer whenever I can.. 646799

- LC158778

Working out great. Thanks for the follow up 614450

- LC158778

It arrived in a timely matter, was able to replace the bad one, with no modifications or problems. Has worked great with about 10k miles on it already. 611478

- LC158778

Works great, no problems 610468

- LC158778

I will not own another 5th wheel without this type of pin box. It absorbs the shock and improves the ride tremendously. It was recommended to me by a friend and I would do the same. Well built and worth every penny. 610437

- LC158778

Works really well. Installed it myself. Definitely smooth out the ride between the pick up and the RV. 609635

- LC158778

Installation was super easy ! looks great can't wait to try it out in the spring ! 588079

- LC158778

Takes the bounce out of the road Helps keep the things in place inside the trailer 576931

- LC158778

We found our new Trailair to be an excellent improvement . The one thing that could use a little attention is the air pillow system. Every time I use the fifth wheel, I have to add air. 564784


Ask the Experts about this Lippert Components Fifth Wheel King Pin

Do you have a question about this Fifth Wheel King Pin?

  • What is the Difference Between the Trailair Air Ride and Flex Air for a Lippert 1621 Pin Box
  • Even though both the Trailair Air Ride # LC158778 and the Trailair Flex Air # LC369535 look similar and incorporate the air bag and shock to help improve your towing experience, the Flex Air has a few upgrades that the Air Ride does not have. The 2 things that separate these 2 5th wheel pin boxes is that the Flex Air has a rubber compound that is built into the head assembly which really helps to absorb road shock. The Flex Air also has a pivoting head which gives you controlled back...
    view full answer...

  • Best Pin Box Upgrade Recommendation for 2017 Grand Design Momentum with a 1621 Pin Box
  • For your 2017 Grand Design Momentum that has a Lippert 1621 pin box the best upgrade we have is the Trailair Flexair part # LC328492. This has cushioning vertically and a pivoting king pin plate that allows for cushioning front to back as well. This will give you a noticeable smoother ride quality than what you currently have.
    view full answer...

  • How to Determine Fifth Wheel Pin Box Model
  • If you are unable to contact your trailer's manufacturer with your VIN to find the factory pin box model number there are some steps you can take which will allow you to determine what pin box model you have so you can purchase a new FlexAir. To do this you will need to follow the steps in the linked help article, which I will go over with you. Start by selecting your pin box style like in the accompanying photo (which you will also find in the help article). You will then need to use...
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  • Weight of Trailair Fifth Wheel King Pins
  • The Trailair Air Ride # LC158778 weighs 184 lbs; the Trailair Flex Air # LC328492 weighs 232 lbs. I have added links to video reviews of each product for you.
    view full answer...

  • Air Ride 5th Wheel Pin Box for 5th Wheel Trailer with Lippert 1621HD Pin Box
  • The Trailair and Trailair Flex Air pin boxes offer fantastic ride quality compared to standard pin boxes and would be the way I would go. But it all depends on the manufacturer and model number of your trailer's pin box. This information should be on a sticker or plate on the pin box itself. If that information is not available there are some measurements you can take to identify it. Use the help article I linked below that explains the necessary measurements if you need to. Once you...
    view full answer...

  • Can Trailair Flex Air # LC328492 Replace Lippert 1621HD Pin Box on a 2017 Jayco Seismic Wave 355W
  • You are on the right track of choosing an upgrade for the Lippert pin box on your 2017 Jayco Seismic Wave 355W. Since the pin box is a 1621HD instead of a regular 1621 you need to go with a different pin box as the Trailair Flex Air # LC328492 is only compatible as a 1621 replacement. If you like the Trailair line then you can use the Trailair Air Ride # LC158778. This is rated for 21,000 lbs and the only difference between this and the Flex Air is that the Flex Air has a pivoting head...
    view full answer...

  • Compatibility of Andersen 5th Wheel Hitch with Trailair Air Ride Pin Box
  • According to our contacts at Andersen, their 5th Wheel Trailer Hitch Systems like # AM3200 are compatible with the traditional Trailair Air Ride Pin Boxes, such as the part # LC158778 that you referenced. The only exception is the Trailair Rota-Flex Pin Boxes, which provide too much forward and rearward movement to work well with the Andersen. Please note that these pin boxes are designed to replace the existing pin box on your trailer. For example, this Trailair Air Ride is designed...
    view full answer...

  • Is Trailair Air Ride Pin Box Compatible with Demco Hijacker Autoslide Hitch
  • Trailair Air Ride 5th Wheel Pin Box # LC158778 is fully compatible with Demco Hijacker hitches such as the 18K # DM8550034 and 21K # DM8550035 which fit short beds fitted with standard above-bed base rails like Demco kit # DM8552025-71. You'll also want to use the Demco Capture Plates for Trailair Pin boxes # DM6171. Pin box part # LC158778 is a correct fit to replace a Lippert 1621HD 5th wheel pin box. This direct replacement will bolt right up in place of the 1621HD and give a smoother...
    view full answer...

  • Replacement Air Bag for a TrailAir 5th Wheel Pin Box
  • There are numerous TrailAir pin boxes that could take replacement air spring # LC432404. Check your pin box for a sticker that has any sort of part number on it and that will tell us which one you have. Air bag # LC432404 is designed for the following pin boxes: Air Ride - Lippert 1621 with 21,000-lb capacity # LC158778 Air Ride - Lippert 0719 with 18,000-lb capacity # LC179879 Flex Air - Lippert 1621 with 18,000-lb capacity # LC328492 Flex Air - Lippert 1621 with 21,000-lb capacity...
    view full answer...

  • Air Bag TrailAir Pin Box has Shifted and is Tilted to One Side
  • I am not sure how the air bag could even move like that. Make sure the shock is adjusted so that the outer sleeve is flush with the top of the arrow on the inner sleeve. You may need to deflate the bag and then re-add the air to get it back into position. there should also be a couple of bolts on top holding the air bag. make sure those are still there and tightened down. It is possible that excessive travel of the shock caused the bag to shift. You may need to temporarily remove the...
    view full answer...

  • Recommended Pin Box Replacement For Lippert 1621 And Fifth Wheel Trailer Weighing Over 19,000 Lbs
  • With the weight you said your trailer weighs when fully loaded, I recommend a pin box that is designed to be able to handle that weight. The pin box I recommend is the Trailair Air Ride 5th Wheel Pin Box, part # LC158778. This pin box is designed as a replacement for the 1621 you have on your trailer and it has a 21,000 lb weight capacity. This system has an internal air bag and built-in strut that helps reduce the jarring and chucking. I have attached a link to a product review video...
    view full answer...

  • Will TrailAir # LC158778 Replace Lippert 1621HD on Big Country Fifth Wheel
  • The 21k Trailair Pin Box part # LC158778 dimensionally will be an exact replacement for the Lippert 1621HD pin box that you have installed on your trailer currently. This will fit and work well for you. The height shouldn't be affected, but if for some reason it was you could use a different set of mounting bolts on the frame of your trailer when you install this pin box to get around that.
    view full answer...

  • Reese Goose Box for a Fabex 663 5th Wheel Trailer Pin Box
  • Reese Goose Box # RP94716 should fit all of the Fabex 600 series pin boxes. The 600 series pin boxes have most of the same important measurements. The only thing that seems to differ is the amount of bolts per side and the overall length of the pin box. Other replacement pin boxes that are a fit for the 600 series do fit the 663 so you should be good to go.
    view full answer...

  • Which TrailAir Pin Box Fits 2019 Grand Design Momentum 351M
  • Since your 2019 Grand Design Momentum 351M has a Lippert 1621 pin box the Trailair Pin Box part # LC158778 will fit and give you a much smoother ride! I attached a test course video link for this pin box to this page for you to check out that shows the cushioning effect in action.
    view full answer...

  • Replacement Air Bag for Lippert Trailair Pin Box
  • There is a replacement air bag # LC432404 for Trailair pin boxes that you could use. The replacement air bag will work with Trailair # LC158778, # LC179879, # LC328492, and # LC369535.
    view full answer...

  • Best Cost Effective Pin Box to Reduce Chucking for Lippert 1621 Replacement
  • The Trailair pin boxes can be used with the Andersen Ultimate like what you have and they provide the best bang for the buck as a cushioned pin box so you'd want the part # LC158778 which is designed for replacing the Lippert 1621. Air bags will stiffen up your suspension, but they really won't make it smoother as they don't provide a smoother ride quality like the name would imply.
    view full answer...

  • Air Bag on Trailair 5th Wheel Pin Box is Tilted
  • I spoke with my contact at Trailair (it was his father that invented this pin box!) and he said that "in most cases the bag had been improperly crimped at the manufacturer. Meaning the metal plates on either end of the bag are a small degree out of alignment, causing it to inflate lopsided as you see in the photo. It doesn't seem to affect its performance, however, some customers feel the need to replace it."
    view full answer...

  • Can Lippert Trailair Air Ride 5th Wheel Pin Box LC158778 Be Used with B&W Companion Hitch
  • The Lippert Trailair Air Ride 5th Wheel Pin Box # LC158778 is a direct bolt-on replacement for the Lippert 1621. If your 5th wheel has a 1621 pin box you can install this cushioned unit to help reduce some of the chucking from your 2-trailer towing set-up. The B&W Companion 5th wheel hitch # BWRVK3500 is not compatible with Sidewinder/Revolution pin boxes because those products change the trailer's pivot point. The Air Ride # LC158778 does not change the trailer pivot point but it does...
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  • Installation Instructions for TrailAir 5th Wheel Trailer Pin Box for Lippert 1621 Pin Boxes
  • There really is not too much to installation of the TrailAir pin box # LC158778. You are going to need some assistants given the weight of pin boxes. But really all you do is unbolt and remove the old one and then bolt the new one in its place.
    view full answer...

  • Comparing Lippert Components Trailair Pin Box To Trailair Flexair Pin Box
  • The Trailair Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs # LC158778 and the Trailair Flexair 18,000 lb # LC328492 are more similar than different. The major difference that you stated is the capacity and the second notable difference is the Flexair 18K has a rubber compound built into the head assembly as the first defense against road shock. If your trailer's GVWR is under 18,000 lbs, I recommend the Trailair Flexair 18K # LC328492 due to the extra layer of shock...
    view full answer...

  • How to Select Replacement Cushioned Pin Box for Grand Design Momentum M349 5th Wheel Trailer
  • I checked the Grand Design website for details on the pin box installed on your Momentum M349 but they do not include that detail in their specs. Usually you'll find the pin box part number on the box's driver's side sticker. This is needed to select an appropriate replacement cushioned pin box that will bolt right up in place of the OEM model. You can use the linked page to select that OEM part to then see the compatible cushioned pin boxes, and cushioned pin boxes that also include...
    view full answer...

  • Determining Pin Box Make and Model to Choose Correct Replacement Pin Box
  • Even though you weren't able to find a sticker or label on your pin box to determine the make and model number, I have a solution to be able to determine which pin box is on your 2011 Dutchman Voltage 3900. Selecting the style pin box and then taking some measurements will help us determine the pin box on your camper. I have attached a help article that will walk you through this process. Unfortunately there is not a way for me to look up which pin box is on your trailer, so taking...
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  • Comparing TrailAir and TrailAir Tri-Glide Replacement Pin Boxes for 5th Wheel Trailers
  • Lippert makes the TrailAir and TrailAir Tri-Glide replacement pin boxes but they have both been around for about the same amount of time. The difference is that the Tri-Glide models have 3 steel rods which act as rollers, letting the bottom jaw glide forward and back during towing. This helps further reduce chucking. Because of this I recommend a Tri-Glide model. To determine if there is one that will fit your trailer I will need to know the manufacturer and model number of pin box itself....
    view full answer...

  • Replacement Pin Box for 2016 XLR Thunderbolt by Forest River Trailer with Lippert 1621 Pin Box
  • You currently have a Lippert 1621 pin box on your 2016 XLR Thunderbolt by Forest River. It's rated for 21,000 pounds and I suggest sticking with that since it's what the manufacturer put on their originally. The replacement part number depends on the reason you're looking to replace your current one: Direct Replacement # LC1387882 21,000 pounds Trailair Air Ride Fifth Wheel Pin Box # LC158778 21,000 pounds Reese Sidewinder # RP61421 19,000 pounds Reese Goose Box Fifth-Wheel-to-Gooseneck...
    view full answer...

  • Replacement Upgraded Pin Boxes for a Lippert 1621 Pin Box
  • Trailair Flex Air 5th Wheel Pin Box # LC328484 is actually not the correct model to replace the Lippert 1621 pin box. Instead it fits the Lippert 0719 pin box so it will not work with your trailer. For your 1621 pin box there are more options: # LC328492 rated for 18,000 pounds # 5AB-E1621-610 rated for 21,000 pounds # 5AB-E1621-16K rated for 16,000 pounds # LC158778 rated for 21,000 pounds # LC328330 rated for 18,000 pounds # LC328329 rated for 21,000 pounds The TrailAir and...
    view full answer...

  • Comparing Lippert TrailAir and Reese 5th Airborne Replacement Pin Boxes for 5th Wheel Trailer
  • If your trailer gross weight is under 18,000 lbs you might consider the TrailAir Flex Air, part # LC328492. The TrailAir pin box you were reviewing, part # LC158778, is a 21,000 lb-rated replacement for a Lippert 1621 pin box. The comparable item from 5th Airborne is part # 5AB-E1621-610; this is also a replacement for the Lippert 1621 and is also rated at 21,000 lbs capacity. (But again please note that the TrailAir is not for use with any type of gooseneck adapter.) I have linked...
    view full answer...

  • Which Air-Suspension Pin Box to Replace Lippert 1621HD on 18,000 Lb 5th Wheel Trailer
  • The HD designation on your Lippert 1621HD pin box does indicate that it is a heavy duty model. Based on your estimated 18,000 lb gross trailer weight you can use the TrailAir # LC158778. I did confirm with my contact that the LC158778 will work in your application. Or you can use one of the other replacement pin boxes such as the Reese # RP61421, which is a sidewinder pin box without air suspension.
    view full answer...

  • What is the Correct Pin Box for a 2018 Grand Design Momentum 376TH
  • According to my research, your 2018 Grand Design Momentum 376TH should use a Lippert 1621HD bolt pattern. Therefore, any of the pin boxes that are designed to replace a Lippert 1621HD should be correct for you. I have attached a list of these for you. If you are looking for a Trailair Air Ride 5th Wheel Pin Box then part # LC158778 should be correct for you. With that being said, trailer manufacturers do not provide us with information on the pin boxes they use so you will need to look...
    view full answer...

  • Replacement Pin Box Upgrade for a 5th Wheel Trailer with Venture CJ13517 Pin Box
  • We have some pin box upgrades that will fit in place of your Venture CJ13517 pin box but there isn't a FlexAir model that will fit. But the other outstanding options are the Demco Glide Ride, # DM8250012, which is most like the FlexAir. It is rated for 21,000 pounds. It has 2 Urethane bumpers help to absorb road shock that do not require maintenance and a parallel linkage system that minimizes chucking. I linked an informational article on these options for you.
    view full answer...

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Info for this part was:

Installed by:
Joe V
Expert Research:
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Jameson C
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Edited by:
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Video Edited:
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