This is a friends truck: 2000 F250 7.3L 4R100 4x4 Manual Transfer Case 170k miles DPC422 NVK5 Build Date 06/00. Transmission fluid level is good. Fluid does not smell burnt but is not the cleanest. No idea if there has ever been a flush. I did not have time to drop the pan. I do not know if it has the original Transmission in it or not. So, it could have the mechanical diode which should only affect 1st - 2nd shifts IIRC. The chip/tuner has been removed and made no difference.

The truck does not move in any gear. This condition developed almost suddenly and supposedly there were no issues shifting prior to this happening. Supposedly there were no loud noises when it began either. It would move occasionally at first. It does have Park: does not roll while in Park, so I will assume that fact alone removes the transfer case from the equation. Additionally, It has a TSS code that comes back when cleared. There are no additional codes that are relevant to this problem. OD light does not blink. There is an occasional/intermittent rattle that is coming from the area of the torque converter that occurs mostly when the truck is placed in Reverse and occasionally in Park and therefore a bit difficult to replicate. The rattle sounds more like someone is sticking the tip of a very small zip tie in a fan blade and it can barely be heard above the engine noise. The other torque converters that I have heard are very obvious when they give up the ghost. I was told that Ford used rivets inside the TC and when those break it can sound like this.

I have removed the electrical connector that serves the solenoid pack on the PS rear of the transmission about 5 inches in front of the rearmost fluid line. The truck still does not move in any gear with this disconnected; however the OD light does flash when it is disconnected.

I have swapped out the DPC-422 with a spare DPC402 XLE4. This did not change anything. I did not have much time to spend with the truck to troubleshoot much more. Just looking for ideas and guidance for the next time I look at it.

If any of the info is incorrect ref troubleshooting, I will happily correct it. Thank you for any assistance.

 

No, it did not have a mechanical diode when it left the factory. That didn't start until the 2001 model year.

That sounds (pun intended!) like a broken flex plate.
There is NOTHING electrical that could cause this. That includes the PCM. No matter what is wrong electrically it will still have 4th gear when in drive, 2nd gear in 1 & 2 positions, and reverse. Since it has none of those that means something mechanical has broken.

 

I tried to respond. But when I finally did, I saw that Mark beat me to it on the response. I would follow his recommendations and look further at those areas.

 

Thank you Mark for the awesome information as it clarifies a lot. I do realize that the mechanical diode did not start until 2001 since we have those approximate build dates on the forum that I believe you provided; however, since we don't know if it is the original factory installed transmission or not and I do not want to assume that it does, I wanted some clarification as to whether these symptoms are consistent with a mechanical diode failure...which I don't think they are?

I had not considered the flex plate. I'll check that next. Thank you!

 

Thank you for your time and effort.

 

the truck cranks and runs---?? how could it be the flex plate??? what m I missing???

 

Just rebuilt one of these trans it did the same thing if I’m reading ur post right it starts but does not want to move on these it is usually the forward clutch it looks like a bucket it pushes the trans it’s not like a normal trans it honestly sounds like a slightly burned trans in need of a slight rebuild the insides of these r very simple n straight forward. If h have any questions feel free to ask kinda a expert on 6.0/7.3

 

Those symptoms are not consistent with a mechanical diode failure.

Good point. I missed that.

It is probably something else that broke. Either way, the trans needs to come out to find out exactly what broke.