Heres one for you guys. Driving along, going camping. Pulling my little 17 foot trailer( 3500 lbs). All is well and almost at the campsite the overdrive lite on my shift **** starts flashing on and off. All operations seem fine on the tow home, overdrive still is usable by pushing the button but the lite keeps flashing. Get home unload and 4 hours later I am droping off the brother in laws stuff at his house. Truck has now cooled off and a noticable hard shifting of the automatic is felt yet was not noticeable with the trailer hooked up. Seems like the shift pattern has changed. I know the flashing lite means a code of some sort, does that mean these trannys have a electronic shift module of some kind and thats what set off the flashing lite. I have a buddy at the ford dealer and he said to stop by and we can check the code but what do the experienced ford owners think. The truck is a 97 f350 crew, psd, 4x4 with a auto trans.

Thanks for any info, I will check back later

Ed

 

The flashing O/D light is the "CEL" of the tranny, so to speak, which means a trouble code has been generated. I'm not big into automatics, but I would guess a valve body is sticking, causing some sort of time delay to be tripped when it's going into gear. To protect itself from excessive slipping, the tranny may dump pressure to the clutch packs, hence the hard shifting. Either way, you need to drive as little as possible to preclude further damage and get it checked out ASAP.

 

Yea as far as I know the flashing O/D light does not mean any specific problem - but rather means that a transmission code has been stored. Just like the SES light means a code was thrown but doesn't always even mean a problem.

I can't give a guess as to what you problem is but I agree with Rancha - don't drive too much until you get the code checked. It could make the difference between a minor and a major problem!!

 

If you do a search on this site you'll find several causes. One is transmission overtemperature, one is the speed sensor in the rear end (this error usually corresponds with your speedo/tach jumping or not working). When this happened in my 97, Autozone's scantool could not find a code. My son took it to a mechanic friend who has a more sophisticated tool and found an error code of "faulty ROM in the PCM. I'm still not sure if this meant the trans PCM, or the engne's. I did however discover that my alternator wasn't working properly. The heater hose that runs across it had broken something in the little box on the back of the alternator. I've gone 120 miles since and the light has not come back on. I'm guessing that the undervoltage caused a code fault because the computer wasn't getting enough juice, but the voltage hadn't dropped enough to throw the low voltage code. I also have read that the hard shifting is a form of "limp home mode" that is designed to reduce stress and temperature by not allowing the clutches to slip as much. It will shift normally after you reset the code. I'd guess that the trans ran hot pulling the trailer. I'd advise resetting the codes by disconnecting the neg. terminal on Both batteries for 15 minutes. If the error comes back, take it in for a scan.
Just my $.02

John
97 F250 Heavy Duty 4X4

 

I had the same blinking light problem one week ago while pulling one of many fully loaded haylage wagons over a long steep hill. At the top of the hill I had to shut the truck off then back on to get it to stop. The next day, and ever since then, I have not been able to turn the overdrive off or on while in the regular drive gear, But I can turn it off and on in any other gear.

 

Just to update, I just got back from my buddy at the dealer. He scaned my truck and a transmission fault code came up, It does not tell you what the problem is though. He cleared the code and on the drive home the truck shifted normally again. He thought that being I was pulling a trailer that the trans may of heated up and caused a clutch or valve to go crazy for a bit setting off the code, once the code comes the truck drives in protection mode. Now that the code is gone all shifting is back to normal. He also said it could be just a early warning of problems to come. As far as I know its the original trans with 304,000 km's on it. My tranny shop told me back when I first bought the truck and had it in for a service and flush that they can get me a new tranny that is really beefed up inside should this one go one day. The price was reasonable too but I cant remember it now. Anyway thats the scoop, thanks to all who replied.

Ed

 

I had that problem with my truck at 17,000 miles. Took it to a dealership they checked codes and said it was speed sensor. Replaced speed sensor left dealership got about half mile light came back on. Went back to dealership rechecked code with new speed sensor and it showed clutch between 1st and 2nd was messed up. I made them get a new tranny and install it no problem since.