Jimmy rolls while in park

Is it a automatic or manuel

IF ITS A auto there is somethin wrong with the park pawl in the tranny

Please tell me a mechanic did not say there is nothing they could do and just to put something behind the wheel?

Oh my.

Anyway. You want to park your vehicle on a level surface and block the tires. Next get underneath the vehicle and disconnect the shifting linkage. Grab the shift lever on the transmission and attempt to put the transmission into Park. You will know when this happens from the familiar click you hear when Park is engaged. Next, unblock the tires and attempt to move the vehicle by pushing it. If the vehicle will not move, then an adjustment is required on the shifting linkage. Just re-block the tires and find where you can adjust the linkage (I do not support the idea of rebending the linkage as this will most likely cause another problem.)

If the vehicle continues to move, then the parking pawl inside the transmission is broken. (This is my guess as a regular mechanic may not want to tear into a transmission, or if he/she is a friend may not want you to incur the cost of this repair and may tell you to "put something behind the wheel".)

Hope this helps. Good luck.