The man was removing the transmission of the pickup truck when the jacks collapsed on him, Auburn Police spokesman Mike Hirman said.
His family found him dead under the truck later. He had recently purchased the older Nissan truck.
They are not sure when the incident happened at the home at 10704 S.E. 304th Street, police said.
The man was living with his daughter and son-in-law at the home.
The King County Medical Examiner was called to the scene to investigate.
The man's name has not been released.