speed problem

99 4x4 navigator 112,000 miles it runs good but the 4x4 and low gear lights stay on , and for some reason this causes my speedometer not to work right ,it will not pass more than 25 miles per hour , sometimes the ligths go off and my speedometer works fine.
Can this be a speed sensor problem?

Can this be a speed sensor problem?

It sure sounds like a VSS.. it might just be loose and misaligned.