I've just finished assembling the Bugatti Chiron (42083), and there's a three-position lever in between the two seats that -- probably -- isn't working: one position connects the wheels to the engine; the other two positions appear to do nothing.

The lever itself moves a gear "collar" (I guess) back and forth; that has three positions, and moves correctly.

What's the lever supposed to do? Where did I go wrong in assembly?

Mysterious lever

  • A quick look at the instructions showed that pushing it backwards would push the interlock forwards onto gears that connect to the red axles, while forwards would push the interlock backwards onto the gears that connect to the yellow axles - I didn't follow those two axles back to see what they connected to though? Jan 8, 2019 at 13:13

1 Answer 1


You have two of three right:

  • One position is the Drive, where the wheels are connected to the engine via the gearbox
  • The middle is the Neutral, where there is no connection between the wheels and the engine
  • And the third should be the Reverse, where the wheels are connected to the engine but with passing through a reverser instead of the gearbox.

This is the relevant part, the lever in question hooks into the gray transmission driving ring in the middle and connects the central axle either to the red or the blue gear: https://farm2.staticflickr.com/1724/42850584481_6feba37f1f_o.jpg

If the reverse is indeed missing, you might have made an error during assembly. Finding and correcting such an error will most probably involve disassembling the whole bodywork and some of the undercarriage, then rebuilding everything back again. For this reason it is generally a sound advice to double-check the parts added in each step and periodically check the already built subcomponents to see if they work as expected.

  • 4
    "For this reason..."; I did; apparently something came adrift when I mated the two halves of the car together. Even as I was doing it, I was thinking that it'd be useful if the instructions had a section of "turn this thing; this other thing should move" at critical points in construction. Moreover, it wasn't clear to me at the time what the subcomponent was for, so "work as expected" wasn't really relevant. Jan 8, 2019 at 14:08
  • We had similar problems with the Technic Extractor and ended up taking it completely apart to reuse the parts for an alternative build. There should definitely be checkpoints along the way to make sure you haven't made some minor mistake. It isn't obvious until way too late.
    – chicks
    Jan 8, 2019 at 18:28
  • 1
    It turns out that the lever works, but in the reverse position, there's a lot of "play" in the drivetrain -- you have to move the car quite far before the engine reacts. That seems odd, but since everything's moving freely, I don't think it's wrong. I had to run it up and down the downstairs hallway, rather than on the dining table, before I got any movement. I think I need to invent some kind of rolling road for it. Jan 8, 2019 at 20:23
  • 2
    I found it much easier installing the wheels and tires at the end of book 1 and testing all of the drive line. If something doesn't work, it is much easier to correct. Aug 24, 2020 at 21:37
  • 1
    @JerryHindman That is what I did too. If you wait until the end to check it is a mess.
    – Tonny
    Aug 27, 2020 at 10:21

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