Police believe thousands of exhaust parts have been stolen from 4x4s in the past six months by criminal gangs that want the precious metals inside, reported The Sunday Times.
Models targeted for metals such as platinum, palladium and rhodium, include Mitsubishi L200, BMW X5 and Ford Ranger.
Mitsubishi Shoguns and Land Rover Discoveries have also been hit.
Cars can be driven to a garage without the converters, but a loud rattle will be heard underneath the vehicle.
They cost up to £2,000 to replace.