1. Is it possible for a blazer parked at the crest of a driveway to slip our of park and roll forward? 2. If it was tapped slightly, not leaving any damage, could this make the vehilce slip out of park and roll forward? 3. If so, would it happen all of the time? Seems it would be a linkage problem. Kindly answer all three questions. Thanks.
There is no known or common design problem like the Fords had in the '70s so that suggests the linkage could be misadjusted or the parking pawl inside the transmission could be worn. Park on a fairly steep hill, then see how hard it is to pull it out of "park". With the pressure on the parking pawl, it should come out of park pretty hard. Also look at how far you have to pull the shift lever before the transmission releases. If you don't have to move it very far, check the linkage adjustment. If it uses a cable, the outer casing could be loose on either end causing the linkage to not go far enough to get the parking pawl fully seated. If a series of linkage rods are used, check for wear in the bushings from rust, and a collapsed engine or transmission mount that changes the relationship between that linkage and the transmission.