ZiL 131 troop carriers were used by Irina Spalko and her Soviet soldiers during their journey to Akator. The hardy Russian trucks were ideal for navigating the thick Brazilian jungle. Indiana Jones, Marion Ravenwood and Mutt Williams were transported in one with Colonel Dovchenko as their guard, however they overpowered Dovchenko and escaped. When Jones used a rocket launcher to blow up the Soviets' Jungle Cutter, a flying sawblade nearly cut the truck in half.
Following Jones, Ravenwood and Williams' transfer to a "duck," Dovchenko took control of the truck. Later, the truck, filled to overflowing with surviving Russian soldiers, arrived at the siafu nesting grounds where Jones and Spalko's pursuit had come to an end. After Dovchenko was eaten by the ants, the Soviets (including Spalko) backed the truck to the edge of a cliff and used it as an anchor in order to rappel down the side of the cliff to escape from the giant ants.
Behind the scenes
The trucks shown in Indiana Jones and the Kingdom of the Crystal Skull were not real ZiL 131s but in fact heavily redressed American Reo M-35s. The historical ZiL-131 was mass-produced in the Soviet Union and then Russia from 1965 to 2003 meaning that the vehicle's appearence in the film is anachronistic.
Although never stated, it is possible that the ZiL left at the top of the cliff was used by Jones' party to return to civilization at the end of the film. It was the only Soviet vehicle capable of being used following the jungle chase (the second duck and Spalko's GAZ 69 were intact but dangerously right on top of the siafu nest and thus unusable, and Marion's duck was destroyed by going over the waterfalls).