basically it returns the gate to the center position. There's also one more at the bottom, for 1st/2nd.
Part #29 will be below part #17. Part #17 should have de-dents on the bottom that will engage with the spring loaded ball of part #34. This will control the travel of the shift cable to stop at the right place for the selected gear. Also gives you part of the feel you get in the shift lever that you have selected the next gear.
Thanks for the re-direct... Assembly tech must have been sleeping on the line when my trans was going down the line.