In order to animate the swing arm on the right, I remodeled the structure on the arm. I separated the two pistons on the side with the upper arm, so that it can move and swing. I deleted the edges in between and bridged for each model, so now they are all separate and ready to get rigged.

I did the same way as I rigged the wheels. I moved the locators under the pistons, so they will follow the movement as the arm is swinging. I combined the two pistons, then aim constrained them with the top locator and point constrained with the bottom locator.