Workhorse Allison Won't Shift Out Of 2nd

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2004 Winnebago workhorse 8.1 with Allison wont shift out of 2nd and speedometer don't work. Switched front and rear speed sensors and will shift but not in overdrive and speedometer still don't work.

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Welcome to FMCA !!

When you changed the sensors around and the shift pattern changed, that would mean a defective sensor.

So you are going to have one replaced at least. The transmission needs information from both to set up the proper shift points.

Having the scan tool readouts would help narrow down the issue.

Do you have a scan tool? some of the simpler ones will not always read all the sections of the control code from all the modules.

I will look and see how transmission sensors and the speedometer signal are related. The OBD-2 codes would narrow things down faster because the shop manuals list each code and the procedure for checking and repairing.

The list for improper shitting, lists Faulty speed sensor,refer to speed sensor DTC's

Loose speed sensor, Loose or damaged speed gear and a number of others. The TCM needs all the sensors to be working to set the control solenoids for each gear.

The Speedometer defaults to 0 if a malfunction, if there is a fault in the speed signal circuit. (PCM circuit)


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Workhorse did not use Allison trans in 2004. It has a 4L85E GM trans.


Actually, they used both GM and Allison transmissions:

P chassis used the GM

W chassis used the Allison

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