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Changing Horn Hook Couplers to Knuckle Couplers

Another beginner Larry asks this question:

“I’m relatively new to model railroading and have numerous cars and engines with the horn/hook couplers. I would like to change over to knuckle couplers. The ones I have tried don’t match the height gauge I’m using. They are a little low. Any help is appreciated. “

8 Responses to Changing Horn Hook Couplers to Knuckle Couplers

  • Mikesays:

    Hi. I’ve found the plastic square spacers that usually are included in the package with the couplers work to adjust to the proper height required. Another issue may be different knuckle coupler numbers. In North America, Kadee, for instance, sells many different item numbers. Most likely, you will need to use all the same part numbers (Eg. #5; #6) These are usually aligned for use with each other, not some #4, #7. etc. Hopefully it helps and doesn’t confuse you more!
    Cheers, Mike.

    • David Krausesays:

      I agree with Mike although a little more explanation may be in order. There are knuckle couplers available that are offset to raise or lower to match gauge height as needed. The amount of offset is is designated by the Kaydee number. Measure to determine the offset required then match that to a Kaydee number and … VIOLA … you have it.

      • Danny Marsosays:

        David, my layout has been in mothballs for 30 years. My problem is 99% of my rolling stock
        Has horn and hook couplers,30 years ago that was not a problem, but now my new Locos
        Have knuckle couplers, I have to change all my stock, but I will have to do it slowly. Your
        Explanation,while trying to help, only confused me more. I thought I could just go out and buy all the same mfg. number and they would all be good. So if I buy all Kadee #5 or #6 I
        Should be alright,am I correct? Thanks .

  • John A. myerssays:


    When, I first started out, i had the same problem. Go to the local hobby shop and see if they, might carry shims in the .05 and .010, I think the manufacturer is the same one that offers greas’em, for the knuckle couple boxes (Kadee #5). The shims go on top of the truck and the screw that secures it to the body of the piece of rolling stock or locomotive, goes through the shim. I was able to make all of my rolling stock and locomotives, have the same coupler height for good or excellent performance.
    Usually, these shims, that I speak of come in a light tannish brown envelope and they are red or grey. Enough, in each envelope to do numberous cars. Also, they aren’t too expensive either. If the hobby shop, doesn’t carry them in the super detail section, then find a currnt Walther’s Catalog and they will have them listed in there.

    Highball the Main,


  • james penglasesays:

    Go to kadee.com This is the Kadee official site. The site will tell you which couplers to use for which types of cars and locomotives. Kadee also has tools you can use to both measure and adjust coupler height, trip pin height and alignment.

  • Newman Atkinsonsays:

    I have seen this several times. In Most cases the coupler boxes are body mounted. In these cases a center shank coupler is usually the way to go (usually using a #5 KADEE). But if you are mounting couplers in the wheel truck coupler mount many are too low. If you are planning to mount these in the wheel truck coupler boxes you may need to get a coupler called an over shank if I got my terminology right (at any rate it is where the coupler is above the center of the shank that goes into the coupler box. Manymodel railroad cars that came with truck mounted couplers you will find had the horn couplers. This is basically the same as a #5 but it comes with the H Clip. The standard KADEE coupler to get for truck mounte couplers is the No 28 Kadee. That one is the center shank but it comes with an H shaped locking plate that holds the coupler firm and in place. KADEE has the over shank or under shank of that coupler if you need to raise or lower those couplers. You will need some patients working that spring coupler and H Clip in place but once it is in you will have a secure coupler. The other manufacturers have similar couplers to install I am sure. One thing you will need to do is cut the small plastic tabs off just inside the truck mounted coupler box. It allows the full swing of the coupler but it also clears the box for the spring to seat in the box.
    One thing I am doing is installing body mount boxes where they used to be installed on the trucks. It is a little bit more work but is worth it if you have turns that can allow your train to make the turns body mounted. Now converting these cars is not that hard but with them now mounted to the body then height adjustment of your couplers is by installing a #208 or # 209 Kadee spacers (sometimes 2 or 3) between the trucks and the body bolster plate But with these type of trucks they are usually mounted to the body by a plastic truck built in pin . What I do is update the wheel trucks without the coupler mount on the truck. I will remove the wheel truck, take some styrene sprue left over from model kits and find one that will fit in the old truck mounting hole and glue in place file level with the Bolster beam and drill a small hole to fit a plastic screw in the new position. Now mount the new truck and if necessary adjust the height by installing the spacers I mentioned above. Bachmann and Tyco railroad cars are noted to need this modification to really bring your car up to speed. Now you will also find that many tyco and Bachmann engines may need to have the over shank couplers and you will probably find that the engines had to have the over shank old horn couplers anyway. As I go through my fleet, If I decide to change and update old cars (especially ones that had truck mounted couplers) I want to make sure that the car is something worth while to update (and many are) because with the addition to changing the wheel truck and body mounting the coupler, will take a little time and a little more expense. But I am here to tell you that the little extra work will pay off in performance. To update your fleet can be cheaper and make your car perform just as good as all these new overpriced cars on the market today. Now mind you that these new cars are mighty fine. But with a little work and some of the things I have said here you can make many of the cheaper cars look and perform very well and sometimes better if you work at it. Add a few new details parts, maybe a repaint (not necessarily in that order) you can make that beautiful car cheaper than most any ready to run car on the market today. One thing about coupler MFG’s The Kadee is probably the Cadillac of model couplers.(at least in HO Scale) But the others are OK too, But the money spent on the Cadillac will hold up to more years of use than several of the plastic ones. Pulling 30 and 40 cars on my layout, is a feat in itself and the weight of that train will show with the plastic couplers. If you are pulling short little trains then cheaper couplers will work too. Also the Heavy Freight on the Shrine Hill is a 40 foot train with 3 engines in the front and a pusher in the rear.
    So is it easy to change and update these cars Yes. Some just need more work than others.
    To tell you the truth the cheap Bachmann and Tyco were usually starter sets and the wheel truck mounted couplers were to help these cars make the sharp turns of the 18 inch radius track. But as my model railroading has evolved my layouts have much shallower curves and switches where now I can handle 30 and 40 foot trains using multiple engines. One last thing if you don’t have a coupler gauge then I recommend you get one. KADEE has them These gauge the height of the floor of your car, checks the height of the coupler, and checks the heights of the trip pin that some folks refer to as a simulated air hose. This gauge is worth the investment. There is also a trip pin adjusting pliers. All this is worth it too. I actually go to the train shows and find some old cars and fix them up. I buy very few new cars. Hope this helps from Newman Atkinson

  • Larry Rushingsays:

    Gentleman thank you for such a quick response to my question. You have been very helpful. Thanks again

  • Jim Moresays:

    I have been using knuckle couplings for years. All brands and had no problems. All my couplers are body mounted. The main one I use is the #5 coupling or its equivalent. I set the trip pin using a strip of 1mm plasticard across the track.The coupling height is set using the Kadee height gauge. To lower the height I put shim between the coupling and the body. To raise the height I put various shims between truck and body. If height is excessive up or down I use offset couplers

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