OD off blinking
 

My dad's '97 PSD F250 has been having a transmission issue for a while now. Ever so often the OD off light will start blinking and the truck will start shifting much firmer. That is all that happens until he unhooks the batteries and clears the code. The code reader he bought for the expedition doesn't pull any codes off the truck. His friends at work are saying because it has two computers, the PCM and one other (I'm assuming they are referring to the FICM) and because of this his code reader can't pull codes. He talked to a guy at a transmission shop and they told him that his TC clutch is probably starting to wear out. They said when the TC does a full rotation that it will trigger a code and make the light blink. This seems logical but, as I said earlier, no codes are available to make sure. He told me the guys at autozone said they couldn't pull codes because apparently they use the same unit. Is this common enough to buy a new TC and start throwing expensive parts at it without knowing for sure? The truck is not even touching a dealership parking lot. He has also been looking around at prices of new TCs and because of the directions of his coworkers he thinks he can just change it out in his garage after removing a few bolts. I'm getting the feeling that regardless of what his coworkers say, this is no easy task that can be done with just a pump jack, a set of wrenches and a change of ATF.

Thanks in advance for any info.

Nope, one computer for the engine and transmission.

If the OD OFF light is flashing, then there is a transmission problem and likely a P1728 code which means slippage. In an effort to "save" the transmission, full line pressure is commanded and you get the harsh shifting you describe.

Time to figure out what the code is and go from there with data.

The problem with the 95-97 PSD trucks is that the PCM cannot differentiate between a torque converter clutch slip or a direct or overdrive clutch slip. The 99-up trucks have an input shaft speed sensor so they CAN.

You can throw parts at it all day long and still not fix it. I recommend actual diagnostics.

Thanks, I emailed my mom and hopefully he'll listen.

Generic code readers (like what autozone uses) will not pull Ford specific codes. Most transmission shops and some engine shops use something like the Snap-On or AutoEnginuity. These will pull the codes when the light is flashing.