My blazer runs fine but my speedometer doesn't register anything and I can't get it to shift into higher gears. Basically I'm stuck limping around at 28mph. When I give it gas my rpms raise but it simply won't make the jump to higher gears. Auto shop replaced distributor and cap, I changed out the speed sensor...... Still no power past first or second gear. If anyone has suggestion I could use an answer promptly considering my blazer is how my son gets to school and I get to my 9-5.