i have a 94 s-10 blazer with a 4.3 vortec in it… its having problems shifting into 3rd gear and overdrive… what might be the cause of this problem?
I am a complete rookie with automatic transmissions, but I would start by looking at whatever it uses to downshift - a vacuum actuator? a cable?
Your best hope is that whatever actuates a downshift is trying to downshift all the time. If it is vacuum, look for a failed hose or a leaking diaphragm actuator at the transmission.
This transmission is fully electronic meaning no TV cable and no vacuum modulator. Unfortunately the 3-4 clutches in this transmission are a weak link and commonly fail. I would have a trans shop check it out and confirm 3-4 failure.