Where is serial on John Deere 2640 tractor?

The location can vary depending on the model year of the tractor, please consult the tractor's manual for the exact location. That being said, some common locations include:

1) On the right side of the tractor, near the front of the engine block.

2) The operator's manual of the tractor might mention the serial number location as well.

3) Underneath the seat, or on a metal plate attached to the underside of the tractor.

4) On the tractor's frame, near the rear axle.