Just bought a 1995 jeep grand cherokee. when taking off it is very slow and sluggish. but if i take off in 2nd gear it pulls much better. will not go into 1st at all. Also it is a 4X4. The tranny never shifts i think its stuck in 3rd gear all the time. The jeep will get down the road with no problem after about 25mph. From starting in drive to 75 or 80 mph it never shifts. could this be something simple or something major? please all help will be great!