Hi folks. I've lurked here for a while and have gotten a ton of useful info. I now have a transmission issue and have searched everywhere I know to and some of the info matches and some doesn't. I thought I would post and see if your deep knowledge base could give me some answers.

Truck info: 2001 F250, V10, auto, electronic transfer case activation (miss the stick in my old Super Duty), 3:73 limited slip running 285's. It's a short box, super cab and, lol, I know a lot of folks are going to say that's the problem. Anyways, here's the history of the problem I am having.

I bought the truck with about 70,000 in the clock. Put another couple thousand on it back and forth to work. Bought a small trailer and a 2 up ATV (about 1700 lbs combined weight). The first time I towed the combination we traveled about 50 miles on the interstate at 70 and when I pulled off the interstate everything seemed to be fine. Several blocks later, I stopped and went around the corner. All off a sudden it felt like the trailer had brakes, which it doesn't, and they were locking up. It pulled the truck down to where it almost stopped. I shifted into neutral and pulled off the road. The truck was idling smooth and there weren't any weird sounds so I started off again. Several blocks later it did the same thing, except this time, before I could get off the road, something released, and not gently, and off we went. Drove the truck to the mountain, rode for the day, and pulled the load back home. When we pulled off the interstate back in town, the truck did the same thing, but just a very light version of it. Now, when all of this was happening, I had a download in the truck, Hypertech (programmer is probably 6 years old and was loaded into the father in laws 2001 V-10 and then taken out), but was only running the octane download, the speedo correction and the increased shift firmness. I had run the truck with the tuner downloaded in it for about a month before I had the trouble and it had worked fine.

I took the shift setting download out of the truck and kept the octane and speedo settings and drove the truck for several more weeks. Loaded up the ATV and trailer again and did a 400 mile trip to the mountains and back and never had a bit of trouble. Even got 14.5 mpg with the truck. About a month after that I was driving home from work at about 50 mph for 5 or 6 miles, slowed down in town and noticed that it felt like the truck was sluggish. I stopped at a light, turned the corner and the truck damn near seized up tight. I popped it into neutral and the truck coasted fine, revved fine and then idled smooth. I shifted back into gear and then truck kept acting like it was going to lock up. I limped it up the hill to the highway, but when I pulled onto the highway it tried to seize up again. I pulled over, again, smooth idle, no weird sounds, no smoke, but the OD light on the shift column kept flashing on and off. I was able to limp the truck the last 2 miles to the house buy driving down the shoulder in 2nd at 25 mph.

The truck has sat at the house for about 3 weeks while I try to figure out what to do. I had to move it yesterday, so i started her up and there were no flashing lights, nothing weird, etc, etc. I moved her with no problem, but then I was babying it.

One other thing. My mechanic buddy and I did a full fluid swap on the truck, including and tranny fluid and filter change, between the two incidents. The fluid that came out of the tranny was a little dark with the expected clutch pack material, but looked good other than that. I checked the fluid after the last incident and it doesn't really smell like it got hot and looks to be the right color.

My mechanic has a friend who is a ford tranny tech who is willing to rebuild the unit with a heavy duty torque converter and a good rebuild kit from Suncoast, with the total bill being about $2,500. I have the money and the kitchen pass and I dig the idea of having a "bulletproof" auto, but am I missing the real culprit here? Could this just be some kind of sensor issue, or something like that? And if the tranny is toast and we rebuild it, what other things should we do? Already planning on a tranny cooler out of a 6.0.

I almost forgot. I used the truck to haul and old Ford passenger van on a flat bed to the recycling yard (14,000 lbs total, according to their scale) with some of the trip being interstate and some in town driving and had no problem at all. This was between the two incidents.

Sorry about the long post, but I wanted to give all the info I know if I am going to ask for help. Thanks in advance, folks!

 

Get the mechanics friend to scan the truck for transmission DTCs with his code reader. The flashing OD light means there is a high probably of a fault and will have a stored code.

Also I would return the trucks tuning to stock until the issues are resolved. If it were me I wouldn't reinstall the Hypertech again but I'm not going to get into that now.

I'd also go over your brake system to make sure everything is good and not dragging. These trucks like to seize slide pins sometimes and not work properly. As you would figure brakes are kinda important especially on a truck this heavy.

 

I would not spend the money to rebuild the trans without knowing what's wrong. Reading the codes is the way to do that. When the OD light flashes a code is stored. It will stay in memory even if the light isn't flashing, unless the battery is disconnected.

 

I appreciate the responses. I will run a scan on the truck and dump the programmer and see what pops up. Thanks.