detach steering gear from intermediate shaft?

'07 Cobalt, electric power steering.

Steering rack is failing. To remove it, the pinion input shaft has to be disconnected from the universal joint that's at the end of the intermediate shaft. On this car, the u-joint has a sleeve that fits over the end of the pinion shaft, locked with a pinch bolt. [1]

The (Alldata) service manual (and everywhere else) just says to remove the pinch bolt and take the sleeve off the pinion shaft. That second part is not going well. I've tried driving a long chisel from below into the pinch slot, and gottten it about half-way off. That seems to be as far as it wants to go, hitting it pretty hard. It's a 10-yr old car.

So, I can keep beating on it, un-promising as that seems. But, I'm hoping that someone has run into this situation, and has a magic bullet.

Thanks.