The drum of the dryer is usually turned by a motor-and-belt assembly. There are two very clear signs that the belt is malfunctioning: You can easily spin the drum by hand when the dryer is off, or you hear a heavy thumping sound coming from the drum when the dryer is running. Here's how to test and replace the drum belt:
Step 1: Locate the belt by removing the back or front service panel. Depending on the type of dryer you own, you may have to prop up the drum to keep it from sagging. Don't let the drum hang; the bolts that hold it in the cabinet could be damaged. Don't remove any more parts than necessary.
Step 2: Identify the belt. The old belt may be threaded around the idler pulley and motor drive shaft. Draw a diagram showing how the pulley is installed so you'll be able to replace it properly. If the old belt is worn or frayed, but not broken, leave it around the drum as a pattern for positioning the new belt; cut the old belt and remove it when the new belt is in position.
Step 3: Remove the old belt from the pulleys and stretch the replacement belt into place. The new belt must extend around the dryer drum and the pulleys. The trick is to align the belt on the drum with the pulleys -- the ribs on the new belt go against the drum.
Step 4: Once the belt is aligned, turn the drum by hand, if possible, to make sure the belt is tracking. You may have to reassemble part of the cabinet to do this.
Some older dryers have a V-belt pulley drum drive. With this system, two or three pulleys of different sizes set the speed of the drum. To change this type of belt, decrease the tension on the idler pulley and install the new belt in the V-grooves of all pulleys. Then place the idler pulley back into position.
With any dryer, make absolutely sure that you replace the old belt with a new one made especially for the dryer. Any difference in belts can change the speed of the drum and cause problems with other dryer components.
Servicing the Drum Bearing
With the back service panel off, check the drum bearing around the dryer drum shaft. You may have to remove the dryer belt to reach it. If the bearing looks worn and dirty, or if it's loose, it should be replaced with a new bearing made for the dryer.
A screw in the center of the drum connects the shaft to the drum. Remove this assembly and then lift off the drum pulley. Support the drum to prevent it from sagging. The bearing fits around the drum shaft and is slip-fit. Pull off the old bearing and install the new one, securing it the same way the old one was held.
On some dryers, the bearing and shaft are held by a U-bolt, and there are two tapered blocks supporting the bearing and shaft. Remove the bearing by first removing the U-bolt and blocks.
When reassembling the bearing unit, make sure the parts go back together the way they came apart. If the part is assembled with shims, the shims should be placed between the bearing and the support channels. Do not overtighten the screws holding the parts; overtightening could cause damage to the bearing. If the bearing has a lubrication wick, saturate it with auto transmission oil.