I have a 1997 jeep grand cherokee 4x4. it wont go into over drive ,on the freeway. my RPMs r high and i dont want to blow my engine, would a tranny flus solve my problem, or not?

look for vacuum connections with rotten tubing...or fallen off entirely...1997 is enough time for them to quit (because they are NOT using the expensive Neoprene....like bmw does)...is a reminder that we have to stay on top of these rapidly degrading rubber parts https://www.google.com/? gws_rd=ssl#q=neoprene+vacuum+lines there is always the unsavory "smoke test" where smoke is puffed into the lines and we can see what needs attention~ could be as simple as a lowered Automatic Transmission fluid level...you should check parking brake on in Park, engine off...fluid level just to the line...if LOW would start looking for leaks possible connection of the fluid line at the radiator~