The problem you describe sounds like a broken belt. The steps below outline how to check for that and disassemble if necessary.
Disconnect Power. Lift Cover on lint filter. Remove two Phillips screws taking care NOT to allow them to fall into the blower housing. Place putty knife in the seam between the top and front panel about 2” in from either side. Push in on clip while pulling control panel forward and tilting putty knife handle up, all at the same time. Same on opposite side. Raise top all the way.
Check for belt on drum half way back on the drum running from left to right. If belt is missing or broken replace with part number 341241 later in this process.
Looking down inside dryer on left and right see a 5/16" hex head screw about 6 inches down. Remove each side while holding front panel in place. Pull top of front panel about 3 inches forward from sides and then pull up. This will disengage the front panel from lower pressure clips and allow you to turn it sideways and expose the dryer interior. Rotate front panel to right to get it out of the way watching to ensure wiring is not damaged.
Place new belt over drum groove side down if old one was broken. Check white idler pulley for free rotation before installing in holes of floor under motor pulley. Replace with part number 691366 if rotation of pulley is not free or if it appears worn. Loop belt with ribs inward and pass through the open space in the idler arm below pulley then pass loop over motor pulley rib side down. The configuration at the motor should now look like the Whirlpool model in the image below:http://www.applianceaid.com/images/belt-config.JPG
Grasp front edge of dryer drum and rotate counterclockwise slowly to align idler and motor pulley and to remove any twists in the belt.
Reverse disassembly process to re-assemble. Good Luck