Our 96 Chev Cheyenne C/K 4x4 is intermittently shifting hard around 20km/hr and 60km/hr. In the old days I might think a vacuum modulator or something but what might it be for a 1996? Is there a number of things I can check? Do I need to get a code checker? Someone said it might be the computer. The fluid is up and I put in a couple of jugs of conditioner a number of months ago
