The McLaren Racing MP4-29 should actually have an 8 speed gearbox.
Formula One used to use the 7 speed gearbox, but they changed in 2014.
Here is a quote directly from the McLaren MP4-29 technical overview:
"McLaren has been using a seven-speed ’box since 1999, but Formula 1 goes a step further in 2014 with the introduction of eight-speed transmission."
I would attach the full document, but it is only available to registered press personnel. If a moderator or developer would like to see the document, would be happy to email it to you privately.