Help! Can't drop the driveshaft in my 00' Z71

I'm trying to replace the rear driveshaft u-joints in my 2000 Z71. I removed the rear u-joint bolts and straps that hold the drive shaft in place and then tried to slide the shaft forward a little so that I could drop it down, but the driveshaft wouldn't budge. The Haynes manual made it sound like as soon as I took off the straps, the shaft would drop down easily, but it didn't. Am I forgetting something? Does anyone have any tips/ ideas? Any help would be greatly appreciated.

you may have to pry the drivershaft forward with a screwdriver. It will slide forward you just may need to use a little force.

Thanks. I'm going to give it another try this weekend. We'll see how it goes...