One of the most common problems
with the Allison transmission is failure of the Neutral Safety Back Up switch. This switch is the single plug style that can
be found on any 01-05 LB7 or LLY. We always recommend to visually checking the
switch on your transmission before ordering. This NSBU switch can be installed
with common hand tools.
Some of the common symptoms of failure are listed here
Gear shift indicator on
dash not following properly