GM Korea and its labor union officially have a new contract following ratification of their tentative agreement today.

The deal was approved by 60% of the 13,247 union members who voted.

It includes a monthly wage increase of 95,000 won ($84), a signing bonus of 3 million won ($2,700) that is payable immediately and a performance bonus of 6 million won ($5,400) to be distributed at the end of the year.

Additionally, the auto maker agrees to end overnight work and to implement two back-to-back 8-hour shifts beginning in 2013.

“We are extremely glad that the negotiations finally are settled and we can all settle down to the mutual goal of growing our business,” a spokesman tells WardsAuto.

Unlike new labor contracts at Hyundai and Kia, the GM Korea agreement does not guarantee new investment in processing equipment to boost productivity, he says. “We invest to do that all of the time.”

The two sides met 31 times since May 17 before reaching a final deal, a period that saw partial strikes cost the company 24,000 units in lost production.

An initial tentative agreement was reached in August, but it was rejected soundly by 81.3% of the union members in a ratification vote. Vague language regarding changes in the shift system that left the company too much “wiggle room” was blamed for the contract’s rejection.

While neither side has disclosed publicly the exact 2-shift formula, the GM Korea spokesman says the formula worked out by Hyundai sets the pattern for all of the Korean auto makers.

That pattern has two 8-hour shifts beginning at 8 a.m. and ending at midnight. The second shift, however, works one hour of overtime, ending just after 1 a.m.

All of the worker unions at GM Korea, Hyundai, Kia and Ssangyong are branches of the Korea Metalworkers Union.

With ratification of the new pact by GM workers, all five Korean auto makers have agreements in place.

Renault Samsung does not have a branch of the KMWU but negotiates a working agreement with its own in-house workers committee.