CV Halfshaft problem?

[GPope]

Hi,
I have a 1998 Buick LeSabre w/3.8
Both hub assemblies were just replaced, because they needed it. Now I am getting a grinding from what I think might be the halfshaft. It happens when you stop accelerating and are more coasting. If you brake, it goes away. As soon as you give it a little gas, it goes away and comes back when you release your foot from the accelerator.
When I am under the car and I grab a halfshaft, how much play (if any) should there be in the shaft. Any other ways to determine this?

Thanks