My F250 runs great until the transmission just downshifts. Also the OD light on the column shift blinks when the transmission goes on independent ops. Is this a common problem with these years? Let me know where I start? Thanks

 

Generally the first place we start with transmission issues is to pull codes, however the '97 PowerStroke makes this tough. You'll either have to go to a dealer and have them check, or invest in a higher end scan tool - like a Bluetooth OBD2 Adapter with the Forscan software.

But you can still try some basic things. Does your speedometer work correctly? Does the needle ever bounce around, or is smooth and steady?

 

The speedometer is not affected by the transmission problems

 

It gets the speed signal from the vss in the rear axle just like the speedometer . So if its bouncing around it could mean something is off. Other things to look at are the high mount brake light. Problems in the wiring there and sometimes led bulbs can throw it off.

 

It's the other way around. The speed sensor feeds the speedometer which feeds the computer. If your speedometer needle bounces around or does weird things, it can impact your shifting.

 

So if the speedometer is not affected then the VSS in the rear axle is out right? You mentioned the high mount brake light, could you tell me a little more? Should I check the high mount brake light?

 

So if the speedometer is not affected then the VSS is not the problem right? You mentioned the high mount brake light, could you tell me a little more? Should I check the high mount brake light? Assume the high mount brake light is the light on the upper rear of the cab? Or should I assume the transmission is the problem?

 

It doesn't rule out the VSS, but you should really get the codes checked.

 

I will check the codes and assume the parts stores (Advanced Auto or Auto Zone etc...) do not offer this kind of testing?

 

That is correct. You need a really good independent shop or a Ford dealer.

 

They can check for engine codes, but their code readers cannot check for transmission codes.

You can do it yourself with a laptop, a $15 OBD-2 bluetooth/usb adapter and the free Forscan software, or a dealership can do it.