For the transmission gearboxes , all IndyCar Series cars currently use a semi-automatic transmission with 6 - speed gearbox operated by paddle shifters .
For the transmission gearboxes , all IndyCar Series cars currently supplied by Xtrac since the 2008 season but with assistance .
For the transmission gearboxes , all IndyCar Series cars currently use a semi-automatic transmission with 6 - speed gearbox operated by paddle shifters and supplied by Xtrac since the 2008 season but with assistance .