Steering Shaft removal

1990 GMC K-1500 Sierra XC Loosened the 9mm bolt that clamps the coupler to the shaft out of the steering box, but wasn't able get the coupler off the steering box shaft. Tried prying, but the rag joint was absorbing all of the movement. The steering shaft wasn't compressing. I thought all steering shafts were splined somewhere along the way to allow in and out movement? There's a plastic cover over the shaft so it's hard to tell if it is splined somewhere. The cover can be moved around but not removed (solid piece).

Tom