The thrust spring pre-loads rack and pinion gear teeth to prevent excessive gear back lash (Play). Adjustment screws or shims may be used for setting thrust spring tension.
Either roller hearings or bushings may be used on the pinion shaft and rack. Usually there are roller bearings on the pinion shafts and bushings on the rack. Rack and Pinion Tie Rods Tie rod assemblies for rack and pinion steering connect the ends of the rack with the steering knuckles.
Note the construction of the inner ends of the tic rods used on rack and pinion steering. They have very large ball sockets formed on the ends of the tie rod. These balls fit into a separate socket that normally screws onto the end of rack. Conventional hail sockets are used on the outer ends of the tie rods. Rubber dust boots fit over the inner ball sockets to keep out road dirt, water and to hold in lubricating grease. There are clamps on each end to secure the dust boots.