96 e150 351w E4OD

So the other day my OD light started blinking and 1st and 2nd started hard shifting at low rpm. At higher RPM is shifts relatively smooth.

So I pulled over and turned off the engine. Started the engine again and my tranny shifted the smoothest it has ever shifted for about 10 minutes and then OD light started blinking again with the hard shifting.

I plugged in my Scan Guage 2 and no codes are coming up. Do I need another device? I thought the tranny codes were stored in the PCM like everything else?

 

The transmission codes are stored in the PCM. You do need a better scan tool.

 

When the OD light flashes and trans hard shifts, does the speedometer show any jumping? Also if you have speed control(cruse) which works, does it hunt the set speed?

Most likely once you read the codes(OBD1) you will get a VSS problem code. This means the ECU is not getting correct speed information from the PSOM(speedometer ). This is a common issue now days as the PSOM(speedometer PCB) ages with bad connections and capacitors.

Before replacing the VSS sensor in rear axle(which everybody does first and problem is NOT fixed), do a search here for "hard shift transmission" in the 87 to 96 Pickup truck forum. There are many threads about this with diagnostic and repair info.

 

What is the part number for the VSS?

I'm getting:

F4AZ-7H103-A

and

DY1123

Seems like the same part?