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AMPLock King Pin Lock for 5th Wheel Trailers - Conical - Ductile Cast Iron

AMPLock King Pin Lock for 5th Wheel Trailers - Conical - Ductile Cast Iron

Item # AMP77FR
Our Price: $250.00
King Pin Locks
Shipping Weight: 9 lbs
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Use this sturdy king pin lock to deter towaway trailer theft. Lock fits over your fifth-wheel trailer's king pin. Resists picking, cutting, drilling and freezing. Tumbler offers nearly 1 million possible key codes. Fastest Shipping and Great prices for AMPLock King Pin Lock for 5th Wheel Trailers - Conical - Ductile Cast Iron. Read our customer reviews of AMPLock king pin locks. Call 1-800-940-8924 for expert service or order your king pin locks part number AMP77FR by AMPLock online at
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  • Reviews (19)
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AMPLock King Pin Locks - AMP77FR

  • Cast Iron
  • AMPLock
  • Keyed Unique
  • Gray

Use this sturdy king pin lock to deter towaway trailer theft. Lock fits over your fifth-wheel trailer's king pin. Resists picking, cutting, drilling and freezing. Tumbler offers nearly 1 million possible key codes.


  • Tamper-resistant, sturdy lock deters trailer theft by preventing hookup
    • Surrounds your 5th-wheel trailer's king pin
    • Prevents would-be thieves from hitching your trailer to their tow vehicle
  • Push-and-lock cylinder locks without the need for a key
  • Rotating-disc-tumbler lock provides maximum security
    • Nearly a million possible key codes
    • Resistant to picking and drilling
  • Heavy-duty ductile cast iron construction
    • Absorbs shock to prevent breaking
    • Resists any kind of cutting, including cutting with a torch or liquid nitrogen
  • Conical design hinders thieves using chains
  • E-coat finish resists corrosion
  • 2 Keys included


  • Inner width: 2-7/8"
  • Inner height: 3-1/4"
  • 5-Year limited warranty

Secure Locking Mechanism

This king pin lock has a disc tumbler locking mechanism. Unlike locks that use vulnerable spring-loaded pins, this ultra-secure lock is bump-proof. The cylinder has a series of rotating discs that can be correctly lined up only when you turn the corresponding key. Two identical notched keys are included to operate the lock. Because these keys feature 1 of nearly a million possible key codes, it's extremely unlikely that another individual will have a key that can open this lock.

U-LPC-VR AMP Lock Conical King Pin Lock for Fifth Wheel Campers - Ductile Cast Iron

Video of AMPLock King Pin Lock for 5th Wheel Trailers - Conical - Ductile Cast Iron

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

Video Transcript for AMPLoc 5th Wheel Trailer King Pin Lock Review

Hey everybody, how's it going Today, we're gonna be going over and showing you how to install the AMPLock kingpin lock for 5th wheel trailers. So this coupler lock again is gonna be a great option for some of those people who either leave their trailer at the campgrounds permanently, or they head into town frequently with their tow vehicle, leaving their trailer unattended. You could also have your trailer parked at the house and you still just don't feel comfortable when you're away at work or if you leave town. This coupler lock here is gonna keep your trailer nice and secure. You don't have to have any worry about someone taking off with it. So this is what our trailer coupler lock looks like installed.

As you can see here, it's very beefy, heavy duty design, it's actually made out of cast iron, so you know it's gonna be super durable as well. Everything has a nice powder-coated finish, sort of this gray hammered finish. So it's gonna do a great job of protecting the lock from rust and corrosion, being that it is, again, installed on the outside here of our trailer, subjected to the elements. So if you haven't heard of AMPlock before, they make some phenomenal products. In fact, their coupler locks are widely regarded as some of the best locking options on the market.

And that's because they're pretty much bulletproof. There's pretty much no way that you're gonna be able to get this coupler lock off the trailer without your key. You can't pry it off you can't cut it off, you can't freeze it off and you won't be able to pick the lock core, due to the tumbler design. So granted, we don't wanna damage the trailer, so we're not gonna be doing any extreme measures, but just again, to show you guys how bulletproof this lock is, we've got a fairly large pry bar here. And if we sneak it below the skid plate here and above the trailer lock, and we really pry on that thing, you can see it is not going anywhere.

In fact, I would probably break this pry bar before the lock broke. So our pry bar didn't work. Let's go ahead and try a hammer now. So if we take a closer look, obviously the lock is still intact and on our trailer, but even where I was hitting this cast iron here with our hammer, it really didn't damage the finish too much. There's a couple of marks here, but most of it is still intact.

So we didn't have any luck with the hammer as well. So that's two out of three that won't work. Let's go ahead and try to pick the lock. Now, even for an experienced locksmith, they're not gonna be able to pick this lock, with their picking tools. I am by no means an experienced locksmith, but just to give you a representation with a standard pick here, you won't be able to free the lock from the coupler. We touched on this a little bit earlier, but due to the tumbler design of the keys, these keys are actually very, very hard to replicate. Now I do wanna point out that if you lose them, you can obtain replacements from the manufacturer. Just make sure you keep your blank here that has your key code, but again, you won't be able to remove this lock by picking it, either. So, something else you'll be glad to know, so with our lock cores here, we don't actually have to have our key to lock this on the trailer. Granted, we have to have the key to unlock it, obviously, but as you can see here, we don't have the key inserted. We'll place it in position. And all we do is just press in on that lock core there, and our lock is engaged. So just another added feature here, you don't actually have to have the keys to lock it on the trailer. So in regards to compatibility, this trailer coupler lock here is gonna work with most 5th wheel king pin pin boxes. There are a few that don't and that's gonna be the Sidewinder options from Reese. There is actually a separate lock for this exact purpose, but most of these standard pin boxes that come on your RV from the manufacturer are gonna work great here with this coupler lock. So our coupler lock here, you can see it's pretty bulletproof, but if anything we're to happen, you would be covered by a five-year warranty. The manufacturer does, however, recommend a quarterly maintenance, but all this entails is simply using a lubricant to lubricate the internal locking mechanism. So to start off our installation today, we're gonna be uncoupling the trailer from the tow vehicle, making sure we're on a nice flat and level surface. Then we're gonna level the trailer with our landing gear. And once we've done that, we're ready to install our coupler lock. We're going to rotate the included cap out and away from the lock core. Then we're gonna take the keys that come with our lock, we're gonna insert them into the core, and then we're gonna rotate them clockwise and then pull out. We'll rotate them back again so we can remove the key. Now, what we're going to do is, we're going to line up the kingpin with the opening inside our lock here. And then we're gonna push all the way up until it's flat against the bottom flange on the hitch. Now, what we can do is simply push in the lock core. Now, we're going to rotate the cap down to lock it in place. As you can see here, our lock is secure on the coupler of the king pin. Now we'll take our keys here. We'll put them in the vehicle or a safe place to where we don't lose them. And then when we're ready to tow, we'll simply open up the little dust cap here. We'll re-insert our key. Make sure you have a good hand on the coupler lock here. And then we'll go ahead and rotate the keys, pull the lock core out, and then we can drop the lock down and out of position. Now we're ready to tow. And that's gonna do it today for our look and installation of the AMPlock king pin lock for 5th wheel trailers..

Customer Satisfaction Score:

Customer Reviews

AMPLock King Pin Lock for 5th Wheel Trailers - Conical - Ductile Cast Iron - AMP77FR

Average Customer Rating:  4.9 out of 5 stars   (19 Customer Reviews)

Use this sturdy king pin lock to deter towaway trailer theft. Lock fits over your fifth-wheel trailer's king pin. Resists picking, cutting, drilling and freezing. Tumbler offers nearly 1 million possible key codes.


Great lock! Your rv will be safe from thieves with this on your 5th wheel. It is VERY heavy and well made. Sometimes you have to hold your mouth just right when taking on and off,


Securely locks my kingpin. Heavy metal gives me that extra confidence when I leave my 5th wheel at the storage place and at campgrounds.

Super happy with this!


Quality, fit, and easy to use. Hopefully one of the best theft deterrents on the market by other reviews. Think the manufacturer should do a video on how difficult it is to defeat this lock it might help to justify the price.


Fits perfectly. Expensive but protects theft of our rolling home.


Well no one has stole the toy hauler from storageā€¦.so far.


Bulletproof design. Extremely heavy con struction.





Fit very well. Just had a little problem with the key # and key code. Doesn't designate which is which. Also, the warranty did not have my product listed on drop down list. But other than warranty registration all is great. Customer service was prompt and attentive.. amp lock received before expected delivery date.


Wonderfully simple yet effective design. Intuitive operation. Nice.


I was a bit skeptical purchasing online, but it fits our Pulltrite Capture Plate like a champion!!
Most definitely recommend this if you have a capture plate that is notched (Pullrite)!


I love this. It is definitely made for the Pullrite and the capture plate. Nice fit and it looks great instead of those gaudy yellow locks. This makes me feel as though my trailer is nice and secure too.


Quality product, easy order process and on time delivery!


Very beefy lock and fit perfectly. Another great buy and interaction with etrailer!


Excellent quality, will take some work to remove without the key. Simple to use, and fits like a glove.





See what our Experts say about this AMPLock King Pin Locks

  • Best 5th Wheel King Pin Lock for Lippert/Curt RotaFlex Pin Box
    The most durable and theft-proof lock I've tested is the AMPLock King Pin Lock for 5th Wheel Trailers part # AMP77FR. The lock itself is very thick, around 10 lbs and it's made of cast iron. It also has a unique key system which prevents picking and eliminates similar key codes. Check out the review video I did below.
    view full answer...
  • Is a King Pin Lock and The Demco Autoslide Locking Plate Meant to Be Used Together?
    The AMPLock King Pin Lock for 5th Wheel Trailers # AMP77FR you mention is for deterring theft, while the Demco Autoslide Locking Plate for MOR/ryde Pin Boxes # DM6025 is designed to prevent your king pin from pivoting inside your hitch. The two would not be used interchangeably and are meant to be used separately. So when you're towing you'd use # DM6025, and when you get to your campsite and unhitch you'd use # AMP77FR to protect your king pin. You could also use a smaller lock like...
    view full answer...
  • Recommended 3" Trailer Hitch Pin Lock and 5th Wheel Trailer King Pin Lock
    I do have both pin locks you're looking for but we don't offer one keyed alike for both. Instead, I recommend using the InfiniteRule Hitch Lock for 3" Hitches part # 34061074-D for the trailer hitch and then the AMPLock King Pin Lock for 5th Wheel Trailers part # AMP77FR for the king pin. I have attached a video I did on the king pin lock below.
    view full answer...

Do you have a question about this King Pin Lock?

Info for this part was:

Employee Lindsey S
Written by:
Lindsey S
Employee Jacob T
Video Edited:
Jacob T
Employee Jonathan Y
Video by:
Jonathan Y
Employee Conner L
Installed by:
Conner L

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