Hi- I just purchased a 2000 grand cherokee limited. All the time 4x4. When I first start the truck, put it into drive and start to go the engine revs real high but the truck doesnt move as fast as it should the transmission is not slipping or it doesnt feel like its slipping. This only happens when its cold and only last about 50 seconds or so. Is this the starts of a bad tranny? I still have 30 day bumper to bumper should I drop it off and get it fixed?