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When you turn on your lawnmower and engage the mower deck, at some point you may hear a squealing sound. This sound is most likely the sound of the spindle bearings seizing up. The spindle bearings are the bearings that allow the deck's pulleys to spin. The process for changing spindle bearings is straightforward and will only take a short while to complete. However, before you can change the bearings, you must have knowledge of how to remove your mower deck from your lawn tractor since this process is different for virtually every mower brand and model.
Place wooden blocks on either side of the mower deck and then lower the deck onto the blocks. Disconnect the rods that hold the deck onto the bottom of the lawn tractor by removing the cotter pins. Pull the drive belt off the pulley on the motor and then slide the deck out from under the lawn tractor. This a general process; your model might differ slightly.
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Take a picture or draw a diagram of how the belts route around the pulleys. This will help you when you go to put the deck back onto the lawn tractor. Once you have a record of the belt routing, pull the belt off the pulley system.
Spin each pulley and listen for squeaking, squealing or grinding. There is no need to change a bearing that is not defective. Only change bearings that make noise.
Remove the bolt that secures the pulley to the spindle shaft with a ratchet. If the bolt spins with the spindle shaft, wedge a piece of wood between the mower deck and the mower blade. This will prevent the shaft from spinning.
Place a hole punch against the bearing casing and tap on the punch with a mallet to drive the bearing down and out of the mower deck. In most cases, you will locate an upper and lower bearing. Even if only one is bad, drive out both and replace them. Remove dirt, debris and grease from the area around the location with mineral sprits and a wire brush.
Place the new bearings into the spindle. They will only go in slightly. Place the old bearing on top of the new one and tap on the old bearing with the mallet to drive the new bearing into the spindle. Do not tap directly onto the new bearing or you will damage it.
Thread the spindle bolt back into place and tighten it with the wrench.
Thread the drive belt around the pulleys and then reattach the mower deck to the lawn tractor.