[427sharpe]

When you lose the band or governors, the trans doesnt 'lock up', it loses whatever gear the band engages. In your case, I think you lost the low band because you lost all forward gears. May have lost a sun or planetary gear too. Only a teardown will tell. You can run a pressure diagnostic on the trans in the car if you have a 300 psi pressure gage with HEAVY DUTY 1/8" line with an 1/8" NPT fitting. The diagnostic pressure port on a C6 is just brhind the linkage that retains the backup light switch. It's a small hex plug. NOTE: DO NOT EXCEED 20 SECONDS TEST TIME IN EACH GEAR OR 2 MINUTES TOTAL TIME---YOU WILL BURN UP THE TRANS!!!!! Hook the gage up to the port, and measure your pressure readings at idle with the brake applied, than compare to the normal:
Neutral---50 to 80 psi
Drive 1 and 2--50-95 psi
Reverse--60-150 psi
If you do this and post the results, I will post the correct diagnostic flow chart to help you find the problem.