Moog Control Arms: CK, K, or RK?

What is the Difference Between Moog R Series and CK Control Arms?

CK, K or RK? We here at Diverse Suspension Technologies get this question a whole lot. If you are putting parts on your vehicle, you want to know exactly what you are installing. It can be hard to do that with all of these letter designations. So here is all that you need to know to clear up the confusion.

Short Answer: R Series is a value-driven replacement part while the CK Series incorporates Moog’s premium Problem Solver components for a better than OE upgrade.

Moog Stamped Arms
Moog Stamped Arms

CK (K): Moog Problem Solver

Starting with the CK and K. Whether you see a “K” designation or a “CK” designation, you are getting the same part. The CK and K are Moogs Premium line of control arms. Utilizing their “problem solver” technology, these control arms address common factory design issues providing a better than the original replacement for your vehicle. Most CK and K control arms include ball joints that are powder coated metal with gusher bearings giving them a long life. Many of these ball joints are serviceable and have grease fittings. The CK and K arms also have problem solver bushings and a precise fit and form for easy installation.

RK: Moog R Series

The RK series is a more value-driven part. Because there are so many different vehicles both foreign and domestic, Moog has introduced the R-Series arms to provide replacements for a wide range of vehicles. The RK arms have OE fit and form geometry alignment, with pre-installed OE style bushings and most include the ball joints. However, these ball joints are not serviceable like the CK arms. All of the R Series arms have Moog validated construction and design, providing a less expensive alternative.

Moog Forged Arms
Moog Stamped Arms

Type and Warranty

Each line of control arms has Forged Steel, Stamped Steel, or Forged Aluminium arms to provide the best style for your specific vehicle. The Premium CK line has a limited lifetime warranty, and the RK has a 3 year warranty that are both handled through our awesome customer service team at DST. Whether you are looking for a “light on the wallet” OE replacement, or a “premium” control arm upgrade, Moog control arms are a great choice for your vehicle.

  1. Edwin Lingle
    Edwin Lingle
    December 8, 2016 at 9:51 am

    I have read many reviews about Moog products. They have an excellent reputation. My question is about the warranty. If I have a Moog part fail, how is the warranty handled.

    • Chelsea Baker
      Chelsea Baker
      December 28, 2016 at 8:59 am

      Hello Edwin! With control arms specifically, Moog offers a limited lifetime warranty for their CK line and a 3 year warranty for their RK line. If you have purchased from us here at DST, just give our awesome customer service team a call (1-888-406-2330). They may ask you a few questions and for some pictures to get a better understanding of the issue. Then once the defective part is on it’s way back to us, we will have Moog send out the replacement part.

      Have you purchased Moog parts before? If so, what has been your experience?

  2. Stephanie
    December 27, 2016 at 8:00 pm

    I am very disappointed with the r series control arms. I am on the second set and needing to get the off my car yet again! They don’t even last more than three months before they are squeaking and need to be swapped out again. Lifetime warranty yea but that doesn’t cover getting them changed every few months because they are a garbage product. Made in China surprise. This time whe I take them off I’m not making the mistake of putting another set on.

    • Josh Daniels
      Josh Daniels
      December 28, 2016 at 10:39 am

      Hey Stephanie,

      Sorry to hear about your experience with those control arms. We know that a squeaky suspension can be super irritating.

      Itโ€™s possible that the problem could be environmental instead of with the part itself. Generally, water or other contaminates getting into the bushings is the leading cause for a squeaky control arm and a little lubrication can usually clear that up, but there could be other factors at play. We sell a good deal of Moog parts to a lot of satisfied customers so we like to get to the bottom of any complaints about one of their products.

      If you would like to give our customer support line a call at 1-888-406-2330 and ask for our onsite ASE mechanic maybe we can get some more details and help you cut that awful noise.

      • Stephanie
        December 28, 2016 at 9:45 pm

        Actually the bushing itself is wearing away. This is only after a few months. The first set I thought maybe was a defective part except both sides were the same. So I get the warranty second set and it’s been maybe four months and here we are again. Same issue. And it’s not installed incorrectly because installer is L1 cert control arms are not rocket science to install.

        I am very disappointed with the r series control arms. I am on the second set and needing to get the off my car yet again! They don’t even last more than three months before they are squeaking and need to be swapped out again. Lifetime warranty yea but that doesn’t cover getting them changed every few months because they are a garbage product. Made in China surprise. This time whe I take them off I’m not making the mistake of putting another set on.

        • Josh Daniels
          Josh Daniels
          January 2, 2017 at 12:02 pm

          Hey Stephanie,

          We are right there with you about those rubber bushings. They can provide a smooth ride and provide a barrier between the metal parts on your vehicle but they just donโ€™t last. Polyurethane bushings can provide better handling and should last the life of your vehicle.

          Rubber Vs Polyurethane

          It sounds like you’re putting your vehicle through a lot so you might consider looking at a hardier bushing set. Here is a blog post comparing rubber and polyurethane bushings if you would like some more information. I hope this helps.

          Has anyone tried replacing some worn out rubber bushings with polyurethane? How did it turn out? We would love to hear about it!

          • wil
            February 21, 2018 at 1:35 pm

            I am not putting my vehicle through anything, dry highways and sunny days, and these moog-crap RK series control arms and bushings are falling part in less than a year. I went to toyota a few weeks after I installed these control arms and they called be back to the repair bay and said these control arms are worn out…

            I bought front lower control arms (RK620524 & RK620525) and fell apart in less than a year. RK=cheap, so cheap the boot on the ball joint is falling apart. the bushings are coming apart. I have very nasty torque steer now. DO NOT BUY. Moog suspension parts and energy suspensions parts will only replace the part with the same cheap part, meaning I will have to take this car apart again-is this their plan all along on selling parts?

          • Josh Daniels
            Josh Daniels
            February 27, 2018 at 2:03 pm

            Hey Wil,

            Our experience with the RK line has been somewhat similar in that RK=cheap. In fact, the introduction of the RK line of control arms by Moog a few years back was specifically with the intention of taking back some of the market share that the flood of cheap Chinese components had consumed. The age old saying of “You get what you pay for” is certainly true here. As a part costs less money, it must be constructed with cheaper components. Though we would all be thrilled to have the quality of a $250 control arm at a cost of $60 each, that’s unfortunately not realistic.

            The fact is, Moog knows how to make these parts right. 5 years ago, many of their control arms were easily over $200 each! They were made with higher quality components and they were built to last longer as was made obvious by the longer warranty on those parts. These RK control arms in comparison have a much shorter warranty at I think 3 years, but when you consider many of the cheap chinese parts they’re competing with have a 1 year or shorter warranty – they still have a far better warranty than the parts they’re trying to compete with.

            Fortunately, the story doesn’t end with “Moog introduced a cheaper part to compete with cheaper parts”. About a year ago we heard that Moog was taking what they had learned with the introduction of their RK line and making some positive changes. They are starting to take many of these cheaper RK control arms and retrofit them with their own high quality ball joints and bushings. My understanding was that they’re trying to do it in a way that doesn’t effect the end price as much, but my honest guess is that it cannot help but make them cost at least a little bit more.

            In the end, it doesn’t do Moog (or any of their dealers) any good to have a product with a 3 year warranty that wont last at least 3 years. Lets hope they take note of those that are more prone to failure and upgrade those first!

        • Nate
          March 16, 2018 at 12:11 pm

          Are you sure that the installer is preloading the control arm. If tightened before it binds the bushings and causes premature wear.

  3. patrick Salerno
    patrick Salerno
    March 29, 2017 at 6:32 am

    Is there a molding difference in manufacture =, rk620718 r-series and ck 620718? Thank you

    • Josh Daniels
      Josh Daniels
      April 3, 2017 at 12:56 pm

      Hey Patrick,

      Both of these parts actually use a Moog certified, stamped steel frame. The main difference between these parts is the ball joints that are installed in them.

      The CK version contains the Problem Solver ball joint which has the greaseable zerk fitting, full-ball metal stud, gusher bearing technology, and other patented improvements on the OE design.

      Thanks for the question and keep ’em coming.

      • John Stires
        John Stires
        July 29, 2017 at 5:29 pm

        The CK is the better LCA but why can’t I find any place that sells the only RK

        • Chelsea Baker
          Chelsea Baker
          August 1, 2017 at 7:22 am

          Hello John!

          I can think of a few reasons you are running into that problem. If you’d like to call or live chat our amazing customer service team they would be happy to help find you the part you are looking for.

  4. Danny
    April 25, 2017 at 8:31 am

    Regarding the CK and RK LCA’s, is there a difference in the bushings installed in each?

    My OEM LCA bushing regularly gets oil dripped on it so I’m wondering if they’re both rubber or something more oil resistant?

    • Chelsea Baker
      Chelsea Baker
      April 25, 2017 at 10:07 am

      Hello Danny!

      Great question! Most, if not all, of the bushings in both the RK and CK control arms are made of rubber. If you’re looking for something more resistant I would suggest going with polyurethane.

      Polyurethane is resistant to heat, road chemicals, other oils, and UV rays. It’s also wear resistant opposed to a rubber bushing which can be damaged after repeated flexing and stretching. Another pro for polyurethane is it should last the life of your vehicle while rubber has the same lifespan as the original (OE) bushings. There are pros and cons to both and if you would like to learn more about it head over to our Rubber vs Polyurethane Blog. Or if you’d like to call or live chat our amazing customer service team they would be happy to answer any questions you may have.

  5. Andrew Crouch
    Andrew Crouch
    May 24, 2017 at 1:50 pm

    Side note about the use of poly in some applications over rubber:
    I will bring up the topic of usage of polyurethane strut rot bushings in classic / vintage cars such as the 1971-1973 Ford Mustang and Mercury Cougar, or the 1972-1976 Ford Torino and Mercury Montego, or the 1972-1979 Ford Ranchero.
    Based on a lot of recent discussion in the last decade or so, there have been catastrophic failures from OEM strut rods {In this case, the “strut rod” is a solid bar threaded at one end for a MOOG K8207 bushing set, and the other end is bent with a pair of holes for being bolted to the lower control arm.} utilizing polyurethane and not allowing for the flex or give permitted by the original rubber design. In the case of most older cars that have been upgraded over the years and increased performance drivetrain and aftermarket big brake systems, the OEM strut rods tend to have failure if poly material is selected.
    This is merely a precautionary statement.

    I will say that for control arm bushings, and related, if the installed is not using the supplied grease or using a grease specific to use with polyurethane material, you may experience squeaking.
    Be it a track car, or a classic Lincoln Mark V, make sure you follow the install recommendations.

  6. asdf@adsf.tld
    February 27, 2018 at 4:27 am

    Great explanation. It isn’t worth anything to me. What I need to know is one thing: WHERE IT WAS MADE, with zero caveats. WHERE WAS IT MADE.

    Used to be manufacturers that were 100% made in america/germany/japan/western-europe, would proudly tell you where their stuff was made.

    Then when most of their stuff was still made in one of the aforementioned areas, they would still clearly inform their buyers through a variety of methods of where stuff was made.

    Now that most manufacturers have their stuff made everywhere EXCEPT for the aforementioned areas, (typically China), they play real coy about where things are made.

    But MOOG is coasting on their former reputation. Just walk the internet. Browse the forums. There’s still gobs of idiots out there who swear MOOG is “MADE IN AMERICA”.

    • Josh Daniels
      Josh Daniels
      February 27, 2018 at 2:08 pm


      In our attempts to answer the “where is Moog made?” question we discovered that the only way to tell where a specific part is made is by looking at the label on the box itself. We have examples in our warehouse of the same part number stocked side by side that are made in different countries.

      Moog used to be a solely “Made in the USA” company, but they have since grown and are manufacturing parts for several times as many makes and models as they did originally. In 2014 alone they expanded their control arms and assemblies with almost 600 new applications and had to expand their manufacturing to provide that kind of coverage.

      It seems that Moog is realizing that many folks are upset about some parts being manufactured outside the US (which was merely done to compete with cheaply made options that were drowning out higher priced, but higher quality Moog parts) and are planning to increase US production of vital parts like ball joints and using American made ball joints and bushings in their RK line of control arms.

      In short, Moog is definitely not exclusively made in America because they can not provide their immense coverage otherwise. They are moving toward having more of their products manufactured in their American factories and improving the quality of the low priced RK series.

  7. Phil
    April 13, 2018 at 5:43 pm

    Moog wheel hubs are garbage. I installed one on the front of my 2001 Buick Lesabre in 2016. In December 2017, four of the five wheel studs sheared off, without warning, while my son was driving on the highway, 150 miles from home. The lug nuts didn’t back off, they were all still intact attached to the studs. I don’t want to hear that they weren’t torqued to spec, because they were. Thank God he made it off the highway safely. The local Advance Auto Parts gladly exchanged it for me. Since then, I have installed two more hubs, each has had speed sensor issues after a few weeks (ABS light comes on). As soon as I can get an American made AC Delco hub, this piece of garbage is going back for a refund. The Moog hub isn’t inexpensive, around $145. I probably would have been better off with the cheapo store brand. Funny thing is the other hub is a Timken (made in Korea), and it has been fine. Any parts made in China are junk, period! The originals all lasted over 120,000 miles. So far, Moog has cost me over a dozen hours of travel and repair time.

    • Josh Daniels
      Josh Daniels
      May 2, 2018 at 8:24 am

      Hey Phil,

      First off, very sorry to hear about you and your son’s experience. I have three kids and I would be furious if I were in your shoes.

      I could take this opportunity to try a spin the conversation in a way that would allow me to say “you should still give Moog a try” but I’m not going to do that. I’m just going to thank God along with you that your kid is ok and wish you both well as you look for a wheel hub.

      I will say that Moog is making moves to bring more of it’s manufacturing back to the USA where they can have more control over materials and manufacturing, but I don’t expect you to buy another Moog wheel hub.

      Stay safe out there Phil.

  8. Peter
    June 25, 2018 at 7:22 pm

    Hi Everyone,

    I have the same issue with the RK series. I’ve installed two of these on my Volvo S40: RK620599, RK620598. Now after ~15k later both ball joints have huge play in them.
    I’ve bought them through and they are saying that I’m still covered under MFG Warranty, but I can only get a replacement of the same exact part. Why would anyone want to put back the same bad quality part again? (That is why they don’t loose too much on warranty claims – most people will not go through the warranty claim process and opt for quality the second time)
    Anyways, I decided to take the warranty parts, drill off the rivets of the ball joints and install TRW or Lemforder joints just to save further extra expenses.


    • Josh Daniels
      Josh Daniels
      June 27, 2018 at 1:41 pm

      Hey Peter,

      I drive an S40 too, 2011 model. Gonna go check on my ball joints after I get done writing this up ๐Ÿ™‚

      Your experience seems to mirror several others in regard to RK series control arms. It should be noted that the ball joints in these arms are not the Problem Solver ball joints that Moog has shown is a superior product when compared with OE and other aftermarket brands.

      Moog offers the CK series arms which have the higher quality ball joints installed, but they are more expensive. Unfortunately, Moog doesn’t currently offer a CK option for these year ranges.

      I am curious if the dealer you went through handled your claim or if they referred you to Moog directly?

      Hope your new ball joints work out. Thanks for leaving the comment Peter.

  9. Ken Schultz
    Ken Schultz
    September 8, 2018 at 1:03 pm

    Let me tell you my experience with Moog control arms / ball joints and Beck Arnley tie rod ends which I believe are both Federal Mogul brands. In summary, they are 100 percent garbage, a waste of money and should be avoided. Don’t purchase!

    I had RK series control arms / ball joints installed on my 2009 Nissan Sentra to replace the original ball joints which lasted at least 150,000 miles. The RK series ball joints failed after about 16,000 miles. The joints were so loose, they needed to be replaced as an emergency repair by a local shop. The ball joints were inspected by the owner who is a ASE Certified Advance Level Specialist and ASE Certified Master Technician. I have confidence the shop did an accurate and honest evaluation.

    I had Beck Arnley tie rod ends installed to replace the original tie rod ends which lasted at least 160,000 miles. The tie rod ends were installed in March of this year to pass the state safety inspection. As the control arm / ball joints were being replaced, the owner told me that the rubber boots on the tie rod ends have splits / cracks. He said that they didn’t need to be replaced at this time and would still pass the state safety inspection. Six months and already splits / cracks is not normal.

    These parts are not inexpensive. Add to the cost of the parts the cost of installation and the cost of alignments, and we are talking about some very expensive repairs.

    I thought I was purchasing quality repair parts, but you are simply living off your name recognition and reputation while selling, as I mentioned above – garbage.

    • Josh Daniels
      Josh Daniels
      September 11, 2018 at 8:08 am

      Hey Ken,

      First off, sorry to hear about your troubles with those RK control arms. We’ve heard from some other customers that the ball joints can be hit or miss, but to be fair the RK series is not Moog’s best work.

      This may not help you now but there is another alternative to your particular situation. Moog does manufacturer a premium lower ball joint for the ’09 Sentra that can be installed on the original (or replacement) control arm. Odds are the arm itself is fine and for much less than you would pay for the RK arms, you can have two of Moog’s premium ball joints.

      Without seeing the other ball joints we can’t say for sure what caused the premature wear, but the Problem Solver lower ball joints use a metal gusher bearing and a full ball stud that are proven to last. This isn’t the ball joint that comes in the RK arm.

      If you feel comfortable renting a press and installing the ball joint yourself you can save some money on top of the lower price for parts. In the end, replacing the original ball joint with the Problem Solver version (which is the quality part you were expecting) would almost certainly get you further than the ball joint on the RK arms.

      Thanks for sharing Ken. Hope this helps someone down the road.

  10. Phil
    September 18, 2018 at 7:34 pm

    Both my car and truck (each 10+ years) needed front suspension work.
    I just bought a set of CK series UCAs for my truck – 2008 Ford Ranger. The OEM arms are forged and the MOOG CKs I received were forged as well.
    I then bought a set of CK series UCAs for my car – 2003 Mercury Marauder. The OEM arms are forged, HOWEVER, the MOOG CKs I received were stamped.
    All the part numbers on the boxes were verified as correct after checking and rechecking.
    When I check the web sites – both for MOOG and the supplier I used, it shows the BOTH the RK80052/54 AND CK80052/54 arms as forged arms for the Ranger
    – HOWEVER –
    They show the RK80038/40 arms as forged and the CK80038/40 arms as stamped for the Marauder
    Why ? this is very confusing.

    Most of the fact checking and research I have done shows a consensus that forged arms are better than stamped.
    I find the marauder fun to drive so I’ll admit I push it at times so my goal would be to have the better quality arms.

    Both MOOG and the supplier I used list the RK arms as the value line and the CKs as the premium line. That being the case, why are the CKs I received stamped ?
    Again very confusing.

    Thanks !

    • Josh Daniels
      Josh Daniels
      September 21, 2018 at 1:18 pm

      Hey Phil,

      This one threw me so I called up the Garage Gurus at Moog and they filled me in.

      Short Answer: According to Moog the forged arm and stamped arm are interchangeable in this application.

      These UCAs fit different makes and models and one of those was a police issue Crown Vic which came standard with forged arms. The forged arms aren’t necessary since this upper arm is a follower and the tech assured me that there were no longevity or stress issues with the stamped steel arms compared to forged in this instance.

      I understand the initial reaction to seeing the two arms next to each other, but in this case the forged arm is overkill according to Moog. The RK part is an OE replacement that still uses the forged arm. I assume Moog used the stamped arm in the CK to bring the price of the premium part down. The big difference in these arms is the CK being installed with a Problem Solver Ball Joint and the RK with an OE equivalent.

      If you just have to have that forged arm you might consider pressing a new Ball Joint into the original arm. You’d want to make sure the bushings are still in good shape but the arm itself should be fine.

      Thanks for bringing this up Phil. I would have wondered about that as well.

  11. Anthony
    September 26, 2018 at 1:33 pm

    I ordered ck series control arm #ck62067 and ck62068 from Rock Auto.And they did not have the serviceable ball joints as described on your site.

    • Josh Daniels
      Josh Daniels
      October 1, 2018 at 12:41 pm

      Hey Anthony,

      You could try asking RockAuto but that’s right, you can’t, because they don’t have any customer service ๐Ÿ™‚

      Anyway, I was as baffled as you were about a CK part not having the Problem Solver ball joint installed so I got in touch with a tech at Moog. They said that this control arm is actually moving to an RK series because it’s a low-volume part. The CK designation on this arm is probably a holdover from when the part was originally introduced. In this case, Moog provides a straight replacement part from the original manufacturer but they don’t make a problem solver ball joint for this model.

      Thanks for bringing that up Anthony. If you have any other questions please let us know.

  12. John Wayne
    John Wayne
    March 22, 2019 at 9:50 pm

    Hi, I cannot find the CK/K version of lower control arms RK621655 and RK621656. It is very difficult to even found those RK versions. I am redoing the entire front suspension (minus shocks and coil springs – I think) with CK/K heavy duty Moog parts all around (notably, my vehicle has the heavy duty 4000# axle). However, I do not think the above mentioned lower control arms do not have the K500050 ball joints in them. I have no idea about the bushing, either.

    1) If I bought the RK versions of the LCAs, would you recommend immediately swapping out the ball joints and bushing for the CK/K versions?

    2) If so, Is the metal frame of the control arm CK/K-level quality, even though the ball joint and bushing are (most likely) not?

    3) If I buy the RK versions of the LCAs,

    • Josh Daniels
      Josh Daniels
      March 26, 2019 at 12:47 pm

      Howdy McLintock :),

      Yeah, I just spoke with one of the techs at Moog and sorry to say there are no CK version replacement arms for that application, and you are correct: the RK arms do not have the Problem Solver ball joints installed.

      To answer your question, I would buy the K500050 ball joints and bushings and press them into the original arms. You would basically be creating a CK version of your lower control arm.

      First off the Moog tech told me that they can’t guarantee that the Problem Solver ball joints would fit the RK arms (though he said they probably would). The K500050 is designed to fit the dimensions of the original arms and since the RK is an aftermarket assembly it does not have to adhere to the manufacturers ball joint fitment dimensions since the ball joints are pre-installed.

      Second, the original control arms on those 3500 vans are stamped steel like the RK arms from Moog so if they’re in good shape you aren’t really gaining anything with the RK arm. With a little wire brushing and some paint, the original arms should serve just fine as long as they’re still structurally sound.

      Third I would check the bushings and see what condition they’re in. If they’re sagging, cracked, or hollowed out it would be a good idea to replace them since you’re already changing out the ball joint. Moog uses an OE equivalent replacement bushing that would basically restore the arm to “factory fresh” if the original is worn out, but they don’t offer a Problem Solver version of that bushing.

      * As a side note, If you are pushing for durability and longevity you could try polyurethane bushings though they will allow more vibration to pass through the suspension to the driver. I was unable to find a poly bushing specifically for this application so you would need to take measurements of the control arm housing and use a universal bushing that fits your dimensions.

      Hope I was able to answer all your questions and if you have any more feel free to leave a comment or give us a call!

      Ride safe John

  13. John Wayne
    John Wayne
    March 26, 2019 at 8:05 pm

    ‘Reckon that’s some might fine advice, Josh. Much obliged.

    Some advice for you, Pilgrim…. Life is getting up one more time than you’ve been knocked down.

    The Duke


Leave a Reply

%d bloggers like this:
Skip to toolbar