2004 freestar
 

Why does my trans occasionally and randomly not shift from 1st to 2nd, until ease up on the gas? No I am not flooring it from stop! Van has 126,000 miles on it. Trans rebuilt by Ford at 62,000. Trnas shop said could be sensor for shift 1st to 2nd. It could be replaced but told that may not be problem. At $300. for sensor to be replaced, not in hurray to do if not a fix!