Since no one has responded, I’m assuming your talking about limiting the gear to 5th.
Manual shift never go above 5th gear.
You should be able to select manual 5th while stopped or even driving.
Your trans will shift up to 5th gear normal while driving, and downshift normal slowing down even to a stop to 1st gear with the selector in M 5th gear.
Oh I see now. This is my first Duramax so wasn’t sure if it was totally manual operation or what when in L. But from what you say it still functions as a automatic just will never go over the select gear of choice. Cool thanks.
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