Chief designer Ben Bowlby was given the brief from Nissan to not design an "Audi copy". Bowlby placed the GT-R LM's combustion engine in front of the cockpit, a layout that has not been used in Le Mans prototypes since the Panoz LMP01 Evo in 2003. Unlike the Panoz's rear-wheel drive powertrain, the GT-R LM powers the front axle through a gearbox located in front of the engine. This was done in the belief Nissan could construct a front-engine car that is faster and has improved stability and efficiency. When designing the car, Bowlby noted the rear-end designs of Le Mans Prototype were limited in size, resulting in poor aerodynamic efficiency and saw the front-end of such vehicles had been largely untouched, "So we thought: why not turn the rules on their head and make a car with lots of downforce at the front? Not only does this give us greater freedom within the rules, but front downforce is generated more efficiently, with less drag. Moreover, with the front end doing most of the work, we could trim out the rear wing and save even more drag, which is invaluable at Le Mans." The chassis was made from carbon fibre which helped engineers in lowering the weight of the car to the minimum limit of 870 kilograms (1,920 lb) as set by motorsport's governing body, the Fédération Internationale de l'Automobile (FIA).
The engine, co-developed by Nissan and Cosworth, is a 3.0 L (180 cu in) 60-degree V6 with dual turbochargers and direct injection, and is seen by Nissan as the most fuel efficient design. Behind the engine and beneath the cockpit is a kinetic energy recovery system using two flywheels developed by Torotrak. The flywheels gain energy from the use of the front brakes then discharges that energy back to the front wheels via a driveshaft running over the top of the combustion engine. The flywheels can also output power to a secondary driveshaft which is connected to a limited-slip differential at the rear of the car which feeds epicyclic gearboxes located in each rear wheel hub, allowing the GT-R to be all-wheel drive if necessary. The combustion engine outputs approximately 500 hp (370 kW; 510 PS) while the flywheel system is intended to have an additional output of approximately 750 hp (560 kW; 760 PS). The company sought engineers from its performance division Nismo for their knowledge on the engine's development, but had problems installing the power plant into the monocoque. Engineers interpreted the regulations set by the FIA and the organiser the Automobile Club de l'Ouest (ACO) differently, causing a minor chassis redesign, and could only be inserted through the front windshield. The developers prioritised efficiency over sheer thrust since the ACO established rules that limited fuel capacity for Le Mans Prototype 1 (LMP1) hybrids to 68 litres (18 US gal).
With the weight bias of the GT-R LM heavier in the front and power primarily directed at the front axle, the wheels are offset to balance the car. Tyres in the front are 14 in (360 mm) wide, while the rear tyres are only 9 in (230 mm) wide. Michelin served as the team's tyre supplier and worked closely with Nissan to determine the correct compound and size for the car's front and back wheels. Cooling for the engine, gearbox, and flywheel systems is located in the nose of the car, allowing the bodywork around the cockpit to be utilised as airflow tunnels. The use of the tunnels required the turbochargers to be placed on top of the engine, exhausting out the top of the bodywork in front of the windshield. The rear drivetrain is designed without traditional halfshafts that would be required to traverse the tunnels, opting instead for the epicyclic gearing system to work around the tunnels. The suspension geometry was carefully refined and consisted of adjustable Penske rear dampers and Öhlins front dampers along with a rear hydraulic anti-roll bar system. The Xtrac five-speed hydraulically-activated sequential gearbox was casted by a Michigan-based company. Cosworth supplied the car's engine control unit for the gearbox which provided power to the wheels via the hydraulic limited-slip differential.
Nissan publicly announced its GT-R LM programme in East London on 23 May 2014. Six months later, drivers began testing the car for the first time in a two-day roll-out session at the Nissan Technology Centre in Stanfield, Arizona. Testing continued into January 2015 at the Circuit of the Americas. Initially planned for a launch in Europe, Nissan North America chose instead to integrate the new car into their Super Bowl commercial, and the film was made during the GT-R LM's testing at Circuit of the Americas. Testing resumed in February at Palm Beach International Raceway which saw the GT-R LM undertake its first running in night conditions, before travelling to Michelin Laurens Proving Grounds in South Carolina that same month for straight line speed testing. A weeks worth or running at Sebring International Raceway in March ended prematurely after two days because of a engine mounting problem.
Nissan intended to enter two GT-R LM's in the 2015 FIA World Endurance Championship (WEC) starting in April 2015, while a third car would be entered for the 24 Hours of Le Mans. By the time of its planned debut at Silverstone, drivers had covered 3,800 kilometres (2,400 mi) with the GT-R LM in testing but its first racing appeareance was delayed until Le Mans because the car twice failed its crash test and was forced to miss the WEC pre-season test session at the Circuit Paul Ricard. The first crash test ended in failure because the car's front roll hoop was damaged. Engineers were also mandated to redesign the car's door because the FIA decided they should have include an anti-burst load but failed its test first time round and the door's structure was entirely altered following its skin cracking. Testing resumed in April with four days worth of endurance running with 2,000 kilometres (1,200 mi) ammassed at the NCM Motorsports Park race track in Bowling Green, Kentucky.