Since you have the 4.0 something isn't right. You're not getting all of the power out of that engine. Since you have a 95 I'll bet that your Cat is partially clogged. There will be no other symptoms other than some power loss. You should be able to run in 5th gear all day on the highway. If your Cat is original or over 80,000 on it should be time to change it.
My 4 YJ banger (with 112,000miles and 30" tires, 2" lift) goes fine on the flats in 5th...65 to 70.
ON Little rolliing Iowa hills. If I drive faster down hill I can usually get to 50-55 at the top with out down shifting. Down shifting I can maintain 55-60 with the wind.