The FAA today ordered Boeing 767 operators to inspect main landing gear (MLG) components and revise maintenance programs after cracks and heat damage to pivot joint components were found during dozens of gear overhauls.

The damaged components included pivot pins, truck beam lugs and inner cylinder lugs, all found in the center of the gear truck between the two sets of wheels. “Heat damage and cracks were found at the pivot joint location [and] caused by the truck pitching motion during normal airplane operations,” Boeing says in a service bulletin.

Boeing says damaged components have turned up on 42 767-200/300/300F MLG checks and on 11 767-400ER MLG overhauls. The earliest case of damage was seven years from delivery, the manufacturer says. There are no reports of in-service incidents associated with the cracks.

The directive (AD 2013-20-12) gives operators of some 420 U.S.-registered 767s about six years from first delivery or most recent MLG overhaul to check various components. Repetitive checks are also required every six years.

The FAA’s directive, based on the Boeing service bulletin issued last year, also instructs operators to install new truck beam and inner cylinder bushings that will reduce friction and heat-build up in the pivot joint. Reducing heat will help prevent cracks, Boeing says.

The directive introduces a revised lubrication schedule of 14 days or 50 flight cycles for the pivot pins. Airfreight operator UPS in comments argued that an interval of 650 flight hours would assure the same level of safety and match up with similar work in the landing gear area, but the FAA disagreed, saying that the number of cracks found justified the more aggressive lubrication schedule.

Aviation Week Intelligence Network’s Fleets database shows significant 767 fleets in the U.S. include Delta Air Lines’ 95 aircraft, American Airlines’ 70, UPS’s 59 and United Airlines’ 56. FedEx, which took delivery of its first 767 earlier this month, has 45 more on order.