Formula 1 commentator Eddie Jordan and German racing driver Sabine Schmitz are to join the new series of Top Gear.
Motor journalist Chris Harris and TV presenter Rory Reid have also been signed to co-present the programme.
They will join Chris Evans and Matt LeBlanc when the BBC Two programme returns in May.
The new presenters were signed after Jeremy Clarkson, James May and Richard Hammond left the programme last year.
Sabine Schmitz will become the show's first female presenter in 15 years. The last was Vicki Butler-Henderson in 2001.
Speaking about her new role, Schmitz said "the chance to combine both driving and filming was too good an opportunity to pass up".
"I've appeared on Top Gear a few times in the past, so I know we're going to have a lot of fun," she added.
Schmitz has already been filming a sequence with Chris Evans for the new series that "will leave even the most hardened speed-demons gasping for breath when it debuts on TV", the BBC said in a statement.
Her fellow co-presenter Chris Harris is well known for fronting various motoring programmes on YouTube.
Referencing the show's cheeky and irreverent style, Harris said: "I'm quite gobby and happy to get into trouble, so I'm hoping I can underpin the programme with journalistic credibility but still cause some mischief."
Newcomer Rory Reid was recruited to Top Gear from the show's 2015 public auditions, but previously presented for CNET's Car Tech channel, and also had a starring role in Sky 1's Gadget Geeks series.
He said: "When I submitted my 30-second audition tape, I knew the odds were very firmly against me, as the auditions were open to absolutely everybody.
"To be the only person to make it through the open audition process makes me immensely proud."
Chris Evans said of his new Top Gear gang: "We really do have a bit of everything for everyone."