I have a 1999 GMC Jimmy with around 130,000 miles on it. A couple years ago, when my husband was taking it up a rather steep hill and the RPMs shot up to 4500 and the MPH dropped down to 5. It got it up the hill and we had it towed. The mechanic said it was fine. I didn't have a problem with it again until recently. Only when the engine is warmed up and has driven for awhile, and I come to a stop, then I go again, around 10 MPH it will jerk rather violently forward and then be fine. Now, when I go up hills, it takes a lot to get up the hill, and once again the RPMs go up to around 4 grand. It doesn't do it every time. What could this be??? I'm thinking transmission, but I can't get a straight answer from anyone.
