Hi I'm new to the diesel truck world, got mine about a year ago. It's a 2000 F250 super duty with the 7.3 it has a tuner and a bulldog turbo housing swap, bigger intercooler pipes and a bigger intercooler, trans cooler, etc. Anyways I did a service on the transmission last year and I'm about to do a service now that I'm going to start using it again, towing and what not (not my Daily Driver). I've put about 10k from last year to this year, we had one big haul from AZ to TX and back a couple trips to California and Las Vegas all freeways. I've noticed my truck is failing to downshift from 3rd and 4th back to first at a stop light. it will downshift from 2nd to 1st, it seems like once it hits drive (3rd) and OD (4th) it fails to downshift, OD light is blinking and no codes or check engine light on. My thoughts are its either a solenoid pack issue or possibly a speed sensor. I don't have a expensive scanner and I don't trust shops frankly, I feel like they're all out to just throw a trans in it and be done. It also idles up when going from drive to park, almost like it's under load kind of makes me think it's a speed sensor hard to determine. Any ideas or thoughts I should try, recommendations, etc. I also used the search and came up with similar but not exact its usually one or the other. Thanks in advance

 

You DO have codes, you just can't read them. You MUST get the codes, or you'll just have to randomly replace parts until you get lucky.

Go to www.forscan.org. Download Forscan, it's free. Their page shows how to select an OBDII adapter. I bought mine from Amazon for less than $30. This will read the codes.

 

ok thanks ill check that out

 

The blinking OD light is your transmission telling you a code has been set.

 

I have a 2000 f350 psd with 4r100. No significant modifications. The truck has 395k miles on it and the previous owner replaced the motor with a ford factory rebuild at about 367k. He had all the paperwork to go with it. He said the transmission was about 5 years old and was an HD unit, but had no paperwork for the trans. I've owned the truck for about 6 months and everything has been great until last week..

​​​​​​I had been noticing there were some rpm surges when cruising at 65 and the rpm would momentarily jump about 300rpm sporadically. I was initially suspecting a cam sensor and planned on replacing it.

Then last Friday, I was towing my 7k lb toy hauler and it just felt like it was working really hard to get going. About 10 miles in at 60mph and i got a OD off flashing light. Just before it started flashing I was noticing the rpm at 60-65 was between 2200-2500 and usually runs about 1800ish at those speeds. I pulled over and checked the fluid, still bright red, no burnt smell and no leaks underneath. I let it sit about 10 min and tried to get going again. I made it about 2 miles before the light started flashing again. Pulled over and now had a drip coming from the cross member and the top of the trans was wet as well.

Had it towed home and a buddy picked up my trailer. I got Forscan setup and this was what I had on a short drive down the street and back. Looks like both shift solenoids were showing a fault. Forscan wouldn't display any transmission dtc's though.

I ran a pressure test today and all pressures were within the range from the 4r100 diagnosis file from this forum. I've been browsing through a bunch of troubleshooting posts and saw wiring could be a culprit, but all the harnesses look good and nothing has touched the exhaust or driveshafts.

A solenoid pack is $300 and I just wanted to get an opinion as to whether thats the right move to make. Thanks in advance

 

I'm gonna tear into it.. replace the solenoid pack, flush it then add the 6.0 trans cooler and an inline filter while im at it.. hope it fixes the issue..

 

Well... That didn't work. I upgraded the trans cooler to the 6.0 cooler since I was going to be flushing the system anyway. Drained the pan and removed the solenoid pack. It ohm tested fine but on the 12v to each pin test, shift solenoid A sounded weaker than the other solenoids.

​​​​​​I got it all back together and flushed, but forscan still shows a fault in shift solenoid A & B. Does anyone know if there is a remanufactured harness for the transmission? Or am i stuck rebuilding this one?

​​​​​The magnet seemed okay, but let me know what you guys think please.

 

I pulled the harness and found this off the bat...


I made the repairs to these wires and checked all the other exposed wires that weren't inside the loom. I didnt see any other signs of wear on any of the harness. I reinstalled the harness and I'm still getting a fault for shift solenoid a and b. I can't find a pinout that seems to match the colors on my harness. I was able to figure out the orange/blue wire is supposed to be for the TCC. Should I just jump in and just rebuild the whole harness or is it possible this is a PCM issue??

 

I appreciate all the help everyone.......

 

It could be the PCM, but it is more likely to be a wiring problem.

 

Thanks Mark.. would these faults showing in forscan be caused by any internal failure or torque converter failure?

 

Yes, both failures.

 

I should clarify, i meant would this fault be caused by some other component besides the solenoids failing?

 

So now I'm here kind of stumped. I just rebuild the bypass valve which had some built up clutch material at the ball seat.I cleaned it up and follwed the sonnax instructions. I got it reinstalled and I was just sitting here idling in park to get it warmed up and I get a fault on forscan for shift Solenoids A and B. I found a new harness for $275. But would anyone be able to confirm if this is most likely my issue? I'm tired of spending money on this and need to get it fixed.

 

Do you want guesses if that's the issue, or do you want to know if that's the issue?

If you want to know, read the codes. Just showing a fault on that screen isn't enough information to replace ANYTHING. What codes are stored?