Characters may repair vehicles given sufficient time and at least some basic tools. This requires a Repair roll that takes two hours per wound the vehicle has (regardless of how many are actually repaired). Attempting to fix up a tank that has suffered two wounds, for example, takes four hours regardless of the result of the Repair roll.
Field work requires at least a toolbox and basic supplies, and subtracts 2 from the Repair roll. An average garage negates this penalty, and an excellent or dedicated facility adds +2.
Each success and raise on the Repair roll fixes one of the vehicle's wounds. With an additional raise above and beyond that required to fix all its wounds, the repair time is halved.
Wrecks: Wrecked vehicles can also be repaired, but it takes much more time and decent spare parts. The time is equal to 1d6 x 10 hours per wound level repaired.
Example: Corporal Tunny has been tasked with patching the holes in a B-17 bomber with two wounds. He's at the airbase with a dedicated garage and thus adds +2 to his rolls. Each attempt takes four hours, and each success and raise removes one wound.
Savage Worlds Deluxe Edition p. 116