General Motors has completed the sale of its Allison Transmission commercial and military business to The Carlyle Group and Onex Corporation for approximately $US5.6bn.

The automaker said it expects to use the funds to strengthen liquidity and support heavy investments in new products and technology, such as its continued energy diversity initiatives.

The sale agreement - made in June - covers substantially all of Allison Transmission, including seven manufacturing facilities in Indianapolis, Indiana and its worldwide distribution network and sales offices.

The production facility in Baltimore, Maryland, dedicated to the production of conventional and hybrid 2Mode transmissions used in GM's retail pick-up trucks and SUVs, will remain with GM.

The Carlyle Group is a global private equity firm with $58.5bn under management. Carlyle invests in buyouts, venture & growth capital, real estate and leveraged finance.

Onex Corporation is one of Canada's largest corporations and makes private equity investments through its Onex Partners and ONCAP family of funds.

The two will have an equal share.