Vehicle with engine power limiting based on clutch capacity

An all-wheel-drive vehicle comprising:

• an engine;
• a primary axle operably coupled to the engine;
• a secondary axle including an input operably coupled to the engine, a first halfshaft, a second halfshaft, a first clutch selectively connecting the first halfshaft to the input, and a second clutch selectively connecting the second halfshaft to the input;
• and
• a transmission having an input coupled to the engine and output coupled to the primary drive axle;
• a power-transfer unit coupled to the transmission and including a third clutch;
• and
• a driveshaft coupling the power-transfer unit and the input, wherein the third clutch selectively couples the output to the driveshaft;
• a controller programmed to, during a power-limiting routine, command a torque to the engine based on closed-loop feedback control such that the torque decreases when a calculated slip of a selected one of the first and second clutches is greater than a target slip of the selected clutch and increases when the calculated slip is less than the target slip.