allison dvt

[1chevy02]

I had my 02 duramax on the dyno the other day and even with the dvt locked in fourth it would still upshift into 5th. It would prevent downshifts but not upshifts. Is there a way to prevent this or do I just reflash the tcm with a higher 4th-5th wot upshift before I put it on the dyno? It was still climbing at 3250 when it was shifting.

[bballer182]

just lockout 5th gear with your gear selector. (hold the T/H button)

[jimter]

just lockout 5th gear with your gear selector. (hold the T/H button)

02's do not have a 5th gear lockout unless you add it by running an extra wire to the TCM and install the updated GM cal/os.

[bballer182]

02's do not have a 5th gear lockout unless you add it by running an extra wire to the TCM and install the updated GM cal/os.

I know what id be doing...:grin:

[1chevy02]

anybody have a writeup on this or know where to find one? And where do I find an updated gm cal/os

[jimter]

Try This
http://www.kennedydiesel.com/docs/Allison%20OD%20lockout%20final.htm

Also Go to and enter your VIN to find the latest Cal
http://tis2web.service.gm.com/tis2web

[1chevy02]

thanks I'll take a look at that