4 Wheel Drive/SUVs: Frond drive train on 96 suburban, cv joints, excessive vibration

Question
I have a 1996 Suburban 1500 4 wheel drive.  last year I put new 10 ply tires on and also heavier shocks, it has 112,000 miles.  Once I installed the tires and shocks I hear a rattling noise when I hit a bump, I have checked the steering components, the shock, the brakes and nothing seems loose.  I finally grabbed the axels for each wheel and they move a little in and out not any other direction.  Is this normal, and is it something to worry about, it is the only thing that I can think of that is making the noise.  I have a trip scheduled for about 1200 miles and am now a little concerned.  Any help would be appreciated.  The frond differential has oil and the axles only move about a 1/4 inch back and forth into the differential and tire.
Thanks

Answer
They will move a little toward the diff and a little to the wheel as this is the CV joints doing their job. as for the rattling that is a lot harder tire you put on the truck and it can cause excessive vibration over bumps. If you checked all of the shocks and they are tight then I would check the torsion bars at the cross member to see if one of the mounts is broken

Matt