It is a torque shock that was on the 85-87 V6's. It has a bracket that bolts to the cradle. It was eliminated on the 88 for some reason. It supplements the dogbone to reduce front to rear engine movement when accelerating and decelerating.
If yours doesn't have much resistance or is frozen, you can get a new replacement from RodneyDickman.Com
[This message has been edited by fierofool (edited 08-01-2020).]