Things You'll Need
Small screwdriver or pry bar
The drive belt of a lawn tractor is the key component that connects the lawn mower's engine to the blades under its cutting deck. Since this belt moves at a high speed when the blades are operating, the belt takes a lot of wear and tear. Eventually you'll need to replace the lawn tractor's drive belt. While it isn't a simple task, it is one that you can do if you have the right tools and some physical strength. It also helps if you have a garage with a level floor.
Changing the Drive Belt
Purchase a new drive belt. Your operator's manual should indicate exactly which belt you need in the parts list, or you can usually find the information from the manufacturer's website. It's hard to get the right belt by taking the old one to the auto parts store because of stretching and wear.
Park the lawn tractor on a level surface and set the parking brake. A clean garage floor is ideal but you can do this project outdoors if necessary. Lower the deck as low as possible to the floor. If your model has wheels, they should be on the floor with the deck just a few inches above.
Remove the grass catcher and the tube that funnels the grass from the mower deck into the grass catcher (if applicable). It depends on the model of your lawn tractor whether these are two pieces or one, or whether there is a grass catcher at all.
Locate the deck locking mechanism or pins that holds the deck on the lawn tractor. Depending on your model, it may have one release for both sides or there may be a separate release on each side of the deck. Release the deck and ease it onto the floor( if it's not already on the floor). If the mower drive belt has a lot of slack from wear in it, it should drop right off the engine pulley as you release the locking mechanism and allow the deck to move to the floor. If not, you should release the belt from the engine pulley.
Make note of how the mower drive belt intertwines between the mower deck and the lawn tractor and whether there are any twists in it. If necessary, draw a diagram so you can put the new belt back exactly the same. With the mower deck on the floor, the belt is going to have some slack to it. Slide the unattached mower deck from under the lawn mower. Remove the belt.
Add the new belt to the mower deck, making sure to fit it into all the guides and to twist the belt in the appropriate places. Push the mower deck back under the lawn tractor. Reattach the deck to the lawn tractor. Make sure the locking mechanism holds the deck securely in place.
Put your leather gloves on to protect your fingers. Slide the mower drive belt around the engine pulley. This is probably the hardest part of the whole process. Use a small, short screwdriver or a small pry bar to help you guide the belt onto the pulley and to protect your fingers. There isn't a lot of room between the mower and its deck, so you may need to improvise with a different tool or a small length of wood. Some mowers have a spring-loaded engine pulley you can gently pull to get enough room to work the belt back on.
Reattach the grass catcher and its connecting tube (if applicable). Make sure the tube lines up with the exit hole from the mower deck.
It might be advisable to snap a picture of the old belt on the mower deck to use as a reference when you put the new belt on.
It’s usually difficult to slip the belt back onto the engine pulley. Don’t use too much force or you might damage the engine or the belt.