Schneider would produce the armour plates and construct empty hulls; Batignolles-Châtillon would make the AVIS-2 turrets. Final assembly was by Renault. In March 1935 Schneider delivered the first empty hull. On 20 May this hull was finished and sent to Satory for tests. When these had been successfully completed on 24 June, another vehicle, the third of the production series, was sent to the STC (Section Technique de Cavalerie) for further testing. The Satory vehicle was fitted with a turret and again tested between 3 and 7 August without serious problems. On 9 August however, the STC vehicle failed to climb a 50% slope, even though the other vehicle had done so effortlessly. This would be the beginning of a series of severe delays. The Army demanded that the gear ratio be changed and on 2 September refused to accept the first batch of twelve vehicles. On 19 October the first modified vehicle was finished and the first eleven vehicles were only accepted in January 1936 and the first AMR 35 taken into service on 22 April 1936. Meanwhile, the Citroën factory had tried to take over the order by developing the AMR Citroën P 103 which had a very novel hydraulic suspension, but this project was rejected. By 22 February 1936 thirty AMR 35s had been produced; twenty more were being worked on. By the end of June 1936 production numbers had reached 76 tanks, 41 of which had been delivered. At that moment however, a very serious reliability problem emerged that was to slow down production considerably. Many mechanical parts proved to be too weak; especially the Cleveland differentials were not capable of taking the stress loads caused by the high speed of the tank. Much of the factory capacity in 1937 was used to rebuild and modify the entire first production batch of 92. On 8 April 1937 Renault was forced to submit two modified vehicles — one of each of the two main versions — for acceptance as "prototypes". This upgrading project did not result in a very reliable vehicle though: in October the Ministry of War was amazed to find out that out of 43 vehicles, of which the differential had already been replaced five times, six were again in need of a new one. From August 1937 the 75 gun tanks of the second and third series were taken into production. The first five