Do Not Shift light

[John Suter]

Rick and Terri,

The "do not shift" light on a Allison transmission
indicates one of the sensors has determined a "fault"
significant enough to potentially cause damage to the
transmission. That fault could be as innocent as "low
sump temperature" or not so innocent.

If it were to occur while the coach was in a gear,
likely the transmission would lock itself into a
single gear (the "limp home" feature) wherein you
could drive to a safe location off the main highway or
to the nearest repair facility. However, under that
condition, were you to shift to, or through, Neutral,
or shut off the ignition, the coach would not again
enter a driveable gear and it could be "tow-truck
time." (Some will add you could "re-boot" the
transmission, but that action might eliminate the
chance for repairs under warranty, and usually removes
the codes from computer memory...)

If the coach is not in gear (apparently your
situation) there will be one or more "codes" recorded
in the transmission control module memory indicating
the source of the problem(s), providing you don't
clear them, or re-boot before you "read them out."
They are "read" by the series of red and amber light
flashes, depending upon your model of Allison. As
each Allison is slightly different I'd suggest going
to the Allison site to download the "codes" or to one
of our Forum friends here, to get a copy for your
model. The Allison folks usually present seminars at
the Rally in the Vally where they distribute the
"code" information, and explain the details.

There are other diagnostic methods to include the
SilverLeaf software VMSpc which can be used should you
want to explore it in the future.

John Suter
2000LXi and prior PT40's


--- trautoranch wrote:

> She started just great then noticed "Do Not Shift"
> light was on, on the
> shift selector. Never seen that light before.
> Looked in the blue book
> and found no reference. Checked all the fluids and
> jacks, but found no
> problem. Has anyone had this problem before? Would
> appreciate any
> input. We were about to pull out for the Lone Star
> BB rally.
>
> Rick & Terri McIntire
> 1986 PT38 8V92
> Patillo,
> TX
> Please Help!
>
>
>
>


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