2004 Chevy Tahoe 4x4

I own a chevy 4x4 tahoe with about 88000 miles .... I have an extended warranty that has expired .... during the warranty I had an issue with the 4x4 selector .... I found sometimes that the truck would engage 4x4 from 2 wheel drive on its own .... whats up with that .... @ 69000 miles the dealer replaced the encoder sensor and called it fixed .... Iam someone who doesnt use 4x4 at all .... now at 88000 miles the problem is back .... the truck engages 4x4 on its own .... I found a trick that seems to work by shifting into nuetral I manually select the 2 wheel option and it goes back to 2 wheel drive .... for a truck that doesnt use 4x4 at all why is this happening .... is this a manufacture recall or what .... any ideas