My clothes dryer spins when nothing is in it, but won't when clothes are in it. I have shortened the spring which pulls the belt tight, and it still won't spin the clothes. Any ideas?

Need to replace belt and tensioner spring, be sure to clean pullys thourghly before installing new belt.

You need to overhaul the drier which includes cleaning it out of deposits and replacing the belt. If you shortened the spring you will need to replace it with one of original length. Any time a drier is old enough to need a belt it's old enough to need cleaning and deposits build up like cement on the inside of air passages and on the blower which can cause a fire or the safety to burn open. This is easy to do. Make sure to clean vent, too. DrTom4444

Really need to have the brand name and model number, but DrTom4444 is right. I recall a Whirlpool dryer from a few years ago where the substituted a slide for the idler pulley and it caused exactly the problem you have now. The solution was to replace it with a standard idler pulley.