I worked in the aviation field for 20 plus years and I always thought the piece was a hydraulic filter. Makes a bit of sense as many high end racing vehicles use aviation grade components. I do think the guy was referring to the t-handle, even though I think his is an incorrect assessment as well.
Wow! The last time I saw Silent Running was way back in 1981. Our hippie history professor made us watch that (as well as the unedited 1974 version of "Hearts and Minds").