over drive light

MY Grand cherokee laredo 1998 over drive light comes on permanently after driving for like one hour but other things work perfectly. Pls what do i do to solve the problem.

Any body there with an assistance.
Yours,
FTI

When you say, "overdrive light" do you mean the "O/D Off" light in the instrument cluster? Have you tried hitting the button to turn O/D back on?

Have you gotten the "Trans Overheat" or any other warning lights?