The new 42077 Technic Rally Car set looks really nice, and even has a built-in steering system which can be controlled by a gear on the top. There's also a fair bit of extra room inside, is there a way to add Power Functions elements to make it remote controlled?

  • 1
    Please add the “Annual-support” tag :)
    – Phil B.
    Jun 19, 2018 at 11:18
  • 1
    @PhilB. I've added that in. Jun 19, 2018 at 12:05

1 Answer 1


With some Power Functions elements and a few extra pieces, it's pretty easy to turn the Rally Car into an RC car.

Here's a quick demo video of my design in action.

enter image description here

And here are the instructions I made for it.

Required extra pieces

First you are going to need some extra pieces:

In addition to that, you will need a Power Functions remote, and possibly some extra pieces to build the remote. If you don't have a remote already, there are instructions for one at the end.


To add power functions, you will need to disassembly it a bit to remove the engine block and manual steering system.

  1. Remove doors.

  1. Remove roof sides.

  1. Remove roof gear and pull the blue pins out one step.

  1. Take the center of the roof off with the front window frame.

  1. Detach the trunk.

  1. Detach the hood.

  1. Remove seats.

  1. Remove fire extinguisher.

Remove manual steering.

Removing the steering system is a little tricky, but doable.

  1. Locate the place where it attaches to the back.

  1. Push up on the grey piece to detach it from the small black pieces, so you can slide it back and remove all the yellow pieces.

All of these pieces should be removed.

Also remove the black and blue pieces that hold it.

After they are removed, the engine block will be easier to remove.

Removing engine block

  1. On the back, locate this area.

  1. Partially detach it temporarily.

  1. Remove the gear and axles.

  1. Reattach the section.

  1. From the underside, locate where the engine block attaches at the back.

  1. Push up to detach the engine block and the white pieces and pins that attached it.

Check alignment

At this point, you going to want to make sure the front gear attached to the gear rack for steering is perfectly vertically aligned like so. If not, slide the pin out and adjust it. It needs to be vertical for the servo motor to attach to it.

Locate pieces

In these sections you removed, you will find some other pieces you will need.

Disassemble them to find these pieces.

Add drive motor

  1. Build this.

  1. From the underside, position it to slide in the back into the differential area.

In this area, you are going to need to add the black gear.

  1. Hold a black gear in place, then slice the axle and motor into the holes.

Add steering motor

  1. In the front, flip up this white panel.

  1. Slide the dark grey in the gear out one stud.

  1. Build this bracket.

  1. Insert it here, then slide the red pins out one stud.

  1. Through the seating area, insert the servo motor into the bracket and push the red pins back in.

  1. Now if the axle is correctly aligned, you can just slide the axle into the motor.

  1. Flip the panel back down.

Adding Battery Box

  1. Build the following.

  1. Slide the batter box into the back here.

  1. On the sides, attach it with the pieces you just built.


  1. Reattach seats.

  1. Reattach hood.

  1. Reattach roof center, and slide the blue pins back in.

  1. Reattach the trunk to the blue pins.

  1. Hold the trunk in the up position, and reattach the roof sides.

  1. Reattach the doors.

IR Receiver

  1. Attach black pins to the receiver, and attach it to the spoiler.

  1. It's tricky, but run the wire through the crack down to the batter box.

  1. Now run the wires from the motors up through that crack, and attach to the IR receiver, servo to blue, engine to red.

Turning the car on.

Turning the car on/off is as simple as opening the hood and switching the orange switch on the battery box.


You can build the following remote with a few extra pieces.

  1. Attach sticks.

  1. Build arm.

  1. Attach arm.

  1. Attach wheel.

Happy building!

  • 3
    This is FANTASTIC
    – Phil B.
    Jun 19, 2018 at 11:20
  • 1
    Great writeup! This is thorough and beautiful. Nice work!
    – jncraton
    Jun 19, 2018 at 14:54
  • 1
    Nice work and write up! I would suggest popping out the steering limiters on the steering rack as well. Much better turning radius without them.
    – Tom H.
    Nov 7, 2019 at 0:50

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