2001 suzuki quadrunner 500 will not stay in 4 wheel drive?

I had a similar problem w/ my '02. It would not stay in 4x4 in reverse. At first I thought it might be internal in the front diff. After removing the front fenders, I decided to try something easy first. I ended up adjusting the engagement lever on the front diff to the rear a couple of notches and then reinstalled and readjusted the shift cable to compensate for the difference. Hope this helps!