[Greg Reimer 7376]

I just had another thought regarding the issue your S-10 Blazer has. It seems that the computer PROM in the GM computer is probably expecting to see a drop in engine RPM after 50 or so MPH,and it doesn't see it. If the torque converter clutch is not applying,it's in a mode of less than 1:1. It's a pretty loose converter, so the discrepancy is being seen between the vehicle speed sensor(which also runs the speedometer), and the engine speed sensor, which is picked up probably by the tach signal in the distributor. The person who suggested that you test the torque converter clutch apply solenoid for proper operation made a good suggestion.The diagnostic trouble code(DTC) would be caused by that excessive engine RPM at that road speed and that seems to all make sense. Identify the DTC, and that should make a proper diagnosis probable. Since you indicated that it was an intermittant condition,then got worse, it's probably something like that. If the trans fluid is all brown,smelly, and full of big particles, then that was probably the result.Good luck with your project!!