97 expo tranny problems

[expo97]

Hey everyone. I'm brand new to the forum and wanted to say what's up and ask a few questions. I just bought a 97 ford expedition XLT 4 x 2. Anyway I love the truck and it drives and handles great. When I bought it I knew and was told of a tranny issue. It will shift into 1st and 2nd but not into 3 and overdrive. When I jump into the truck I have to turn the OD off so that the RPM's won't rev high. I only use it for city driving and rarely will I go over 40. Is this a tranny problem or could it be the transfer case shift motor? Everything is strong including the motor and the RPM's never go above 2500. Any ideas. Thanks everyone