My van has begun acting up when past about 3/8-1/2 throttle and shifting from 1st to 2nd. It is the 3 spd auto and when it goes from 1st to 2nd under the described conditions it makes a horrible bang and one time even shuddered for a good second or two vibrating the whole van. Is there a band adjustment needed or am I about to be one mad Caravan owner??