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How to Replace a John Deere 613 Bush Hog Gearbox

The John Deere 613 Bush Hog has a 6-foot cutting swath and a heavy-duty gearbox. When mowing a field, it can be difficult to see debris that might damage the mower. While the Bush Hog is equipped with a heavy-duty gearbox, if the mower strikes something such as a metal spike, the gear teeth can suffer extreme damage. There are no replacement gears to substitute when the gear teeth strip. Replacing the gearbox is the only option. This job takes about 45 minutes to complete.

Park the mower on a hard, level surface. Pull back the collar found at the end of the driveshaft going into the gearbox to slide off the driveshaft.

Place a jack under the front of the mower and jack stands under each corner of the front end. Lift the mower until you see the rotary cutter and then lower the jack until the rotary cutter can rest on the jack stands.

Under the mower you will find a metal bar bolted to the bottom of the gearbox. Plug the air wrench into the air compressor and remove the bolt holding in the metal bar using the air wrench and a deep well socket. Brace the metal bar with your opposite hand. Slide the bar off once it is free.

Remove the four nuts holding the gearbox to the frame with the air wrench. Pull off the gearbox from the top of the mower. Slide in a replacement gearbox and align the bolt holes with the holes in the frame. Reinstall the bolts. Tighten the nuts to the bolts underneath the mower. Reinstall the metal bar and tighten its bolt down with the air wrench.

Lift the jack until the jack stands are clear. Remove the jack stands and lower the mower. Pull back the collar on the driveshaft and slide it back onto the gearbox.

Remove the oil fill bolt with a crescent wrench. It is found on the right side of the gearbox. Fill the gearbox with 90W oil. Reinstall the bolt after the mower is filled with oil.

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