I recently inherited a 1996 Jeep Grand Cherokee, just under 90,000 miles. It has been struggling going uphill which is an issue considering I live in a mountainous region. I'll be cruising along at 60 mph and as soon as I start up an incline, the speed drops drastically. If I try to give it more gas it instantly goes into overdrive and kind of stutters when it finally switches gears. Cat, water pump & drive belt have all been replaced in the past 8 months. I've taken it to several places for a diag (including a jeep dealership) and no one can tell me what is wrong with it. Any ideas? It also starting making a thudding noise when put into reverse. Not sure if that's a related issue or not. If you have any ideas what it could be, please let me know!!!!