Trouble shooting and Anthony's advice above led me to GEM. Got used one on eBay, disconnectedness battery, installed. Problem seemingly resolved but, on test drive. When auto trans shifts to 2 new gear, stalls and speedo says I am going 70-100 mph? If I shift the selector to low (1) 2wd, sputters but does not stall when his 5 mph and shifts to second...idles for 15 min after install and then sputtered around neighborhood for 30 min as a post said it would re-set itself after a while...bad GEM?....suggestions?

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1998 Ranger XLT 4.0 Ltr 4WD, no power accessories, auto trans, 56K miles