Veteran performers and R&B icons, Marilyn McCoo and Billy Davis, Jr., are sharing the secrets to the success of their 35-year marriage in a new tell-all book.

McCoo and Davis co-authored Up, up and Away: How We Found Love, Faith, and Lasting Marriage in the Entertainment World.

"While we don't have any magic formula, we definitely feel that an important element that's worked for us is our friendship" McCoo told Canada AM's Beverly Thomson.

The singers, who met as members of the hit '60s group, Fifth Dimension, said they were friends before they fell in love.

However, they're burgeoning relationship didn't always go smoothly.

"As long as we were buddies, we were fine. As soon as we fell in love, we started arguing daily," McCoo said.

"We point that out because we want people to know that arguing is not always a bad thing. It can be healthy. It's a good way of expressing your concerns and keeping communication patterns open," she said.

Despite achieving success in their careers -- eight Grammys and platinum selling albums -- the couple has had their share of musical and personal downfalls.

After the hits stopped coming, McCoo struggled with the notion that she was only defined by her career.

In the book, she wrote, "I was puzzled that I could feel so hollow even though Billy and I had a good marriage, excellent health, financial security beyond our wildest dreams, and a certain measure of fame."

Davis has also had his own set of problems, including heavy drinking and fighting prostate cancer.

"Marilyn helped me with that. We got on some research and figured out what to do. Thank God that our faith kept us through it," he told Canada AM.

McCoo added, "That's what marriage is really about. When you're there for the long haul, you're going to go through troubles, arguments, challenges, illnesses, and it's really special to know that you have someone there at your side who's going to be there with you through thick and thin."