'92 Automatic, 2wd, won't stay in Over drive

[Motorhead]

I am working on a '92 with the automatic. The owner says it will drop out of overdrive while on the freeway just cruising along, no hills. The OD button is operational. He took it to a local trans shop and they say that the trans itself is fine. Any help appreciated.

 

[ZedMikey]

Does it go in and out between OD and 3rd? Try checking the TPS adjustment.

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[ZedMikey]

Forgot to add that it could be the VSS, too. Does the speedometer stop working when it drops out of OD?

 

[Motorhead]

ZedMikey, It will go out of OD and won't go back in. My friend at the trans shop put a volt meter on it while driving and said that the voltage at the TPS was over 4 volts just going down the road. Who is the best priced source for a new TPS?
I will as the guy about the speedo dropping out.

 

[Shadrach]

The sensor is Cummins P/N 3621094 When it goes the O/D will kick in and out. Shad