I just bought a 1987 GMC W4500 42 with a 4 sp auto and 4 cyl turbo diesel made by isuzu and I need some help. What does the 2 green bars flashing under the word econo mean. And what does the econo switch do? This thing won't shift higher then 2nd gear what could be wrong with that? The vacum light comes on for about 5 seconds after startup after all other lights have gone out. Thanks for any help!