I just finished the D11 bulldozer. The last LEGO set I built was 55 years ago, now I got this big machine and I really enjoy it!

But I have troubles with the the calibration and I think the failure is in the gearbox.

What is the best method to reverse engineer the D11 for error correction?

If possible, I don't want to totally rebuild the whole set.

  • 2
    Without any specific details of your issue there is only one option - rebuild the portion that is causing the issue and paying attention to all the details.
    – Alex
    Jan 26, 2023 at 7:09
  • I think it is the best way to fix the problem.
    – Jeeplego
    Jan 26, 2023 at 7:52
  • 3
    If you can tell us more (what actions you took, what did you expect to happen and what happened instead), provide photos or a video of the failure then we might be able to help. Otherwise the most that can be advised is to compare your model to photos or videos found on the internet (hoping you can spot something different) or try to trace the faulty function from either the motor or from the effector end.
    – zovits
    Jan 26, 2023 at 12:14
  • How complicated is a rebuild, I’ve got the same problem 🥲 Feb 8, 2023 at 10:30
  • The correction was therefore difficult because many parts had to be dismantled to get to the error. The error already happened during the first construction steps. But many elements can be dismantled as a whole. In the end, I had some parts left over that I still don't know where they belong. All this was a satisfying work!
    – Jeeplego
    Feb 10, 2023 at 9:03

2 Answers 2


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I made a major rebuild of the D11, opened the gearbox, and found this orange Changeover Rotary Catch in a false position on Step 110 (Page 107) of the instructions. After the correction, the D11 runs fine.

  • 2
    Well done! Don't forget to accept your answer if it did indeed solve the original problem :)
    – zovits
    Jan 30, 2023 at 9:51
  • 1
    Thank you for your recommandation.
    – Jeeplego
    Jan 30, 2023 at 10:24

Sometimes the calibration failure can be solved by reinstalling the control+ app.

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