Originally Posted by
CookieFlow
Well after 1 hour 30, the car is reassembled and it was indeed the problem !
Ps : The left wheel doesn't turn at the same speed as the right wheel when dragging it on the rear wheels or moving the spur gear manually.
Is it something I should be concerned about?

Thanks you so much for the help guys !

It should turn the same speed as the other wheels. Maybe you got a bad bearing or something binding that left wheel.