Wierd acceleration

Hi, My 2006 explorer has 211k kms on it and have noticed that on the highway between 100 and 120km/hr when accelerating it feels like its in too high a gear or the overdrive is locked in because it has a low rumble when accelerating. it also engages a second or so after pressing the gas from a full start like the engine revs a bit then it engages. seems wierd to me. I have a p0349 and p0345 code stored. the engine light comes on and off intermittently. My obd2 code reader is not capable of CAN.