Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# 00574A.
ALLISON LCT1000 NO SHIFT, SPEEDOMETER ERRATIC/INOPERATIVE, DIAGNOSTIC TROUBLE CODES (DTCS) P0721, C0237 POSSIBLE ANTI-LOCK BRAKE SYSTEM (ABS) LAMP ON. SI BULLETIN 1408789. *TT