Delta MD88 at Grands Rapids on Aug 7th 2014, gear problem after departure

A Delta Airlines McDonnell Douglas MD-88, flight DL-1312 from Grand Rapids,MI to Detroit,MI (USA) with 140 people on board (air traffic control read back 40 people), was climbing out of Grand Rapid's runway 08R when the crew requested to level off at 4000 feet reporting a problem with the landing gear. The aircraft subsequently returned to Grand Rapids, the crew advising they had three greens, and landed on runway 08R about 20 minutes after departure.