Decoding the gearbox of the LEGO Technic 42110 Land Rover Defender

After my review of the LEGO Technic 42110 Land Rover Defender I received a lot of questions about the gearbox, how it works, does it really runs inverted, did I make any building mistakes etc. I decided to create another video to show the gearbox in details, demonstrate why I think it runs the other way around and give anyone a chance to take a closer look
at my build and find any possible errors.

Besides the video demonstration here’s a little written summary about the drivetrain of the Defender.

In a normal car the engine drives the wheels through the gearbox, in a LEGO car this is the other way around. By pushing the car the wheels are driving the fake engine through the gearbox.

If we take a look at the bottom of the car we can see that both axles have a differential and the wheels are driving a central differential. There’s a 8T/24T gearing on both axles, which means the speed of the wheels is significantly slowed down.

The power from the central differential is transmitted to the DNR selector through a series of gears.

If the DNR selector is in drive mode then the power is transferred to the right side of the vehicle to the hi/lo selector.

Here you can see that low mode the power coming from the wheels is again geared down. This is incorrect, as it will make the fake engine run slower. In a real car at a constant wheel speed a lower gear means a faster engine.

After the hi/lo selector the power is transmitted to the gearbox through an axle and it comes back on the other one.

And at the end it reaches the fake engine through a series of gears in the front.



  1. Hi,
    First of all, thank you for sharing this information. I learnt a lot. Too bad I didn’t check your videos before building mine. As now I see my rear wheels are moving in the opposite directions, making the Defender not able to move at all. Just wondering, is there an easy way to fix that without pulling apart the whole thing? Just can’t fathom spending another weekend making it again :(.

    Cheers and great work!

    • I guess you have the differential reversed. Don’t think you need to take it apart completely, you need to be able to disconnect the steering arms holding the hubs to pull out the axles from the differential. There are a couple of things to remove for this operation but should not be too difficult.

      • Would you please explain this in more detail? I have the same issue as the commenter above. And it seems like other people are having the same problem as well, as I also saw people mentioning it on Reddit and Facebook. The front and back wheels are moving in opposite direction.

        • If you check steps 4 and 134, you need to make sure that the orientation of the dark bluish gray piece (the differential) is the same as on the picture and not turned by 180 degrees.

          • I had same problem with back wheels not rotating same direction. Read your thread at turned the differential, but still did not help. So noticed the problem was with the creamy colored rotator (dont know the correct word) which connects to the dark grey differential. So the creamy rotator does not spin (rotate at all). Removed it conpletely and now the back wheels spin to same rotation.
            But can you help with this creamy colored rotator? Why is it stuck so it doent spin?

          • If you remove any gears the drivetrain won’t work. If a gear is stuck you need to check why it does not rotate, which element is stuck in the drivetrain.

    • Hi I’ve been meaning to get around to this and the lock down feels like a good excuse. Everything on my defender works apart from the pistons going up and down when I push the car along. But if I open the the rear door and put my thumb across the two grey cogs they move, so it seems they are connected. can you help?

  2. I just turned the rear differential 180 degrees. Was a bit of fiddling – but I am currently starting fase 3, so I was relieved to find that it was not that much deconstruction. Carefully remove the lower wishbone and you are able to reach the diff. Don’t drop the small parts into your model. I did. Was nerve wrecking shake but I retrieved it and was able to remove and rebuild the whole thing within 15 minutes. Good luck!

    • rotated the diff. Not turned. Sorry.

      • Yes I had problems with the rear wheels turning opposite directions , checked that both differentials were in correct position bu5 found that rear one was jammed and would not rotate. After reading various blogs on here and rechecked I found that at step 65 , I had inserted the dark grey bit
        part no 6261374 upside down meaning that the beige coloured rod coming from the diff could not rotate . Managed fairly quickly to rectify and problem solved.

  3. Anyone had an issue with the wrong size gear wheel on page 28. First instruction it shows grey 24 teeth it’s too big. Beige gear seems to be the correct size.

  4. I should remember to rotate the gear box when I get the model!
    Thanks for the memo!

  5. hello! I found the rear of the car sitting very low on its base and the rear wheels almost touching the wheel arches.

    This is very low compared to the front end, what have I done wrong in the build, and how can I correct it please?

    I checked the speed build review n seems didnt do anything wrong 😣😣

  6. My rear wheels are moving in opposite directions. How can I fix this?

  7. After I built my defender, when rolling on the floor, the wheels do not drive the gears at all in any gear, the defender rolls smoothly however.


  8. I have the same problem here. When rolling on the floor, in all DNR mode, the wheel move smoothly, but not driving the gear to move. However, when I lift up the defender, the wheel can drive gear in D and R mode.

    I notice one thing, when I move the grey wheel at the end (like in the video), the gear move together with the wheel. However the wheel is in opposite direction, please see the youtube link.

    And the bottom looks like this

    I have crossed checked the differential, I cannot spot anything. Any idea?

  9. I’ve finished it -looks outstanding- but it doesn’t roll in any gears and i’ve check the differentials allignment and compared it to the instructions and neither me or my dad have spotted the problem therefore we can’t fix it.
    Any other possible solutions?

    • Disconnect the 2 shafts to and from the gearbox and check the whole drivetrain section by section, you can roll most of the gears manually (you’ll have to remove the body for this)

  10. Hi Racing Brick.

    As far as I’m aware, I’ve done everything by the book… (of course!) However, I’ve just got to placing the steering wheel on and find the front wheels seem to be seized? The steering wheel won’t manoeuvre either way for some reason. Is something too tight or have I got something wrong?

    Please advise because I’m loath to continue when I may have a chance to rectify!

    Absolutely loving making this!

    Many thanks,


  11. Ref. The seized steering column.. Panic over! I finally worked it out. I mistook a # 4211553 for a # 4210658! It was stopping the big long black shaft thing from turning freely. Easily rectified so I can continue my Christmas build 🤓

  12. Do your wheels spin backwards if you drive it forward and lift it up in high gear? Mine does.

  13. I ‘m having a problem at step 271. The black gear doesn’t have enough room (in terms of height) to seat on top of the grey gear. By any chance did you have a similar problem when you were building?

  14. Not sure what I’ve got wrong as it all looks right but the rear diff is locked – if I force it (a few inches) the rear wheels will turn in the opposite direction to the front – looks like I’m going to pull the whole back end to bits again

    Also, the gear selector mechanism operates but I can’t see what it actually changes the two grey hubs seem to just move freely

    • If the rear wheels turn in the opposite directions to the front ones then one of your differentials is turned by 180 degrees. Both of them should face the same direction.

      • After i completed the entire build i struggled with some of the problems already mentioned. Rebuild the entire rear end and the vehicle is still struggling. Noticed problems with steps 62-63-64. When pushing in the long grey shaft l64) its under an immense tension, going together with difficulties to push in the blue plugs (63). After doing this everything seems to seize, an idea what to do now?

        • I had the exact same issue and figured out that it was caused by the small gear in step 3. I believe you, as I did, have used the slightly larger black gear, while if you look closely on page 6,the correct size gear is indicated 1:1,and should be gray. Hope this helps 🙂

  15. I’ve fitted the rear diff correctly (same as front diff), but it just seems to lock whenever I try to get both wheels rolling. They’ll run independently (in opposite directions), but, unlike the front diff, the rear diff will never rotate. The whole mechanism seems to seize – so I don’t get the engine cylinders moving etc.

    Have rebuilt the rear-end about four times now as I wondered if I’d somehow missed a step, but and am getting frustrated: just feels like something is loading up the cog wheels somewhere in the gearbox and stopping the whole thing from working.

    Do you know if there’s an easy fix?

    • It’s very difficult to identify the issue without seeing it, there’s no easy fix for “something is stuck somewhere”. I suggest to remove the body completely, and start to follow the drivetrain from each axle and try to find where the issue is. You can disconnect the shafts to and from the gearbox, that also helps to run the different sections independently to narrow down the area where the problem is.

    • I’m having the same problem. Did you solve it?

      • I had a similar issue with the rear gear blocked and it was the part in step 68 having been mounted in the wrong way and blocking the beige axle.

      • I had a similar issue with the rear gear blocked and it turned out that the beige axle was blocked by the part mounted in step 65, which I turned the iron way round.

  16. My problem with the gear box is that R works fine, N motor does not move when wheels moving, D does not work at all? Any solution? Cheers!

  17. I am on pack two of the set, and my front wheels don’t turn when I turn the steering wheel. I actually had a leftover beige gear when I finished so I must have done something wrong. Please help.

    • If you have a leftover gear then it is missing somewhere. Go back and see where that kind of gear was supposed to use and check if it is missing in your build.

  18. OK. I looked inside and saw that there was a gear between the tires that don’t connect to anything. Is that where it goes?

    • I suggest to have a look at the instructions and see where it goes

      • After i completed the entire build i struggled with some of the problems already mentioned. Rebuild the entire rear end and the vehicle is still struggling. Noticed problems with steps 62-63-64. When pushing in the long grey shaft l64) its under an immense tension, going together with difficulties to push in the blue plugs (63). After doing this everything seems to seize, an idea what to do now?

        • I’m sure something is not properly aligned or pushed in place in the assemblies, there should be no tension. Verify the components of the gearbox sub-assembly to ensure there are no unnecessary gaps.

  19. Should the steering wheel turn the wheels by pack 2?

  20. Building land cruiser 42110. I think I finished the first part wrong. When I turn the shafts for steps 88 and 89 They turn the gears from the assembly started on step 33. But the wheels are not engaged. Step 94 does turn engage and disengage the orange fin from the gear arrangements. When turn shafts from step 88 & 89, I feel the gearing difference. But again none of this engages the wheels. Only when turning the shafts from step 85 do the wheels engage. Before I disassemble and start 2+ hours of work again, I thought I’d checkin.

  21. Just built mine and this has happened to me… bloody hell haha

    Ill leave it for another night!

    Great video anwrite up though

  22. I have the same issue as many others here – finished the build but the front and rear wheels turn in opposite directions when you turn one set or the other. I have checked and my three differentials all exactly match the alignment of yours in the second image above.

    What else could be causing this?

    • What happens if you turn the central (red) differential manually? All wheels should spin in the same direction.

      • Yes they do turn in the same direction then – but when I turn the small grey gear in the middle right at the back the front and rear go in different directions.

        • Not sure which gear you’re talking about but that can be normal (depending on the gear). Can you push the car forward on the ground?

          • I mean the small grey cog right at the very back behind the rear differential. I can roll it in certain gears (and in neutral) but in high gear it grinds to a halt as the front and rear wheels work against each other. Something odd somewhere but i can’t find where!

          • That’s normal, when I turn it the front and back wheels turn in the opposite direction. Since the 2 differentials are joined in the central differential before the DNR selector and the gearbox it would be highly unlikely to have the front and rear gears turning against each other only in certain gears. Did you check the alignment of the U joints already based on my other video?

  23. Ah ha. Yes pretty sure that’s my problem! Thanks so much. Hadn’t seen this video previously. Not sure how easy it is to get to them now, but I have all the same symptoms. High gears are much worse and I get the build up of tension so that the wheels spin backwards when you lift it up – like a wind up toy almost. Quite frustrating that such a tiny detail has such a big impact. Any idea how easy or difficult it is to get to them now the build is complete?

  24. Niels van der Ploeg

    I have a problem with my LEGO Land Rover Defender. If I put the gearbox in N or R (it doesn’t matter if it is in LO or HI) the Defender rolls smoothly forward, but when I switch the gearbox in D (LO or HI) and I drive the Defender forwards (or backwards) ), I can’t push it further at a certain point (I think it crashes) and when I release it, it will drive back a little (or when I push the Defender back, it will roll forward). Does anyone know how I can solve that?

  25. I have a problem with my gearbox, when in R the engine runs fine, the pistons are spinning a little slower than in your video though. In Drive mode pistons don’t move.

    I’m a little frustrated and a very ashamed to be asking for advice in a public forum about building a LEGO set lol, I would like to understand the issue given that I even rebuild the rear part convinced I found the issue.

    Here are some pictures:

    thanks so much!

  26. Did you try to push the car in multiple different gears, also in Hi/Lo? In some gears you need to push the car around 1m until the pistons start to move. In R the whole gearbox is bypassed so that’s why the pistons move almost instantly.

  27. I added a motor like in your video, will record it when I got a chance

  28. Hello! First of all I would like to thank you for all your videos on this set that already helped me so much with the building process, but I’m still getting a lot of cracking noises when the higher gears are engaged. I checked the alignment of the universal joints many times and also the other gear that you show in the video. Is there any other critical point that I should check to get rid of the cracking?
    Thanks a lot in advance!

  29. Hi.
    I just finished my Defender and for some reason the left and right side of the wheels go in different directions. One side goes forward and the other backwards or the other way around.

    Do you have any suggestion ?

    Thanks in advance!

  30. Hey! Thanks for all the help you provide to people. It’s really saving a lot of people a lot of time.

    My issue: The rear wheels go in the opposite direction of the front wheels when I turn/push them. And vice versa. When pushing the car it goes about half a meter or so, it starts to provide resistance, followed by a semi-loud “crack” where pistons, shafts and axels suddenly do all the movement that somehow was kept back by the mentioned resistance. This only happens in D, where as in R everything works wonders.

    What I’ve tried: All differentials are placed exactly as described in the manual. I’ve redone the universal joints 10 times, but to not effect. All gears (and cogs on the entire car) seems to work without issue when testing them each manually. Removing one of the joints solves the resistance issue, but then the engine won’t work. Have you got any idea where the error might be?

    Worst case scenario I’ll have to re-do the entire engine, gears and shafts. Or just leave it in R..

    Anyway, thanks in advance!

    • It’s hard to tell what’s wrong based on this, everything needs to be perfectly aligned to make it work. I’ll do another video on the Defender in 1-2 weeks where I will show all the possible issues and traps during the building process, hopefully that’ll help.

      • To bring an update to this:
        I had a look at your “decoding the gearbox” video earlier and decided to compare it with my own the front and center diffs were moving in the correct direction, but the rear turned the opposite way in comparison to your video. I’ve started to take off the entire back and check every step again.

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