My family has6 Isuzu Troopers 85, 88, 93, 2 94's, and 96. In both 94's and the 93 the transmission is starting to act up. In the 94's around 150,000 miles it simply stopped shifting into 4th all the time. We would have turn off the car and restart it and then it would work most of the time. Now that trick is loosing it effectiveness. The 93 will shift into 4th but only under accel when you back off to level off speed it immeaditely down shifts. All transmissions have been regularly flushed and looked at and no where has been found. Is this a common occurence what is the repair.