overdrive lockout

[chagburg]

If you have to have the TCM updated to accept the overdrive lockout switch, does the dealer do this as an update for free, or does it cost? What exactly do you ask the dealer to do and how do you know if you need the update?

[mdrag]

chagburg,

The TCM calibration software update was made available by GM on or about 03/24/2002. I understood that the switch installation was not covered under warranty. However, you may be able to get your dealer to the reflash the TCM (if it is needed) by complaining of shift busyness while towing.

Try installing the ODLO switch following the detailed instructions (http://www.kennedydiesel.com/docs/Allison%20OD%20lockout%20final.htm) found on Kennedy's website. If the switch works, then a TCM is not needed. If the switch does not work, then approach your dealer for the TCM reflash.