In July 1938 a prototype of a lengthened "chenillette" was presented by Renault. It had a fourth bogie in the suspension to reduce track pressure and a third return wheel. To save weight and better dampen shocks the number of leaves in the leaf springs was reduced from six to three. The tracks were obviously longer too, with 156 instead of 131 links. The bin was also "longer" at 72 centimetres, but less "wide" with 123 cm. Internally a new centrifugal ventilator type was fitted. The total length increased to 335 cm, the weight to 3.67 metric tons. Trials took place between 13 July 1938 and 8 February 1939, during which the vehicle was again modified. The top speed without trailer transpired to be reduced to 32.7 km/h; unsurprisingly the trench crossing ability was improved to 160 cm. As the air outlets had been placed higher, the wading capacity was improved to 45 cm. However, the main purpose: ameliorating suspension reliability, was not really achieved. Tracks were still thrown, track guides bent, springs broke and entire bogies were sheared off, just as with the series model.