1997 Ford F150 stuck in 4 wheel drive

I've lubricated the linkage and can shift easily between 2 and 4 wheel high and low but the 4 wheel drive indicator on the dash remains on when I shift back into 2 wheel drive. I can tell its not an erroneous indicator light as the truck feels and handles like its in four wheel drive even though I've definitely shifted to 2 wheel drive. Dave