I have a 1996 F250 PS 7.3. Today my truck was shifting really hard as i was towing my trailer. Shortly afterwards i noticed my overdrive light was flashing. Any suggestions would be great.

 

Get your codes checked and Autozone, O'reillys, or the like can't check them. You'll have to go to a ligit shop with a true diagnostic computer. The light is flashing because it senses an error with the transmission. Think of it as the check engine light for your tranny.
Mine started the same thing in March or April. When you clear the codes it will run fine but when there is a slip sensed(as little as 50 rpms) the OD light will come on again and you will be shifting hard. It is in "limp" mode at that point and jacks up all the line pressure causing hard shifts. Mine ended up being a bad torque converter. I took the opportunity to swap to a 5 speed. Good luck but get it checked.

 

Take about $2700 out of your bank account and find a good tranny rebuilder.
Spend the money on tranny cooler and torque converter.

 

Thanks for the replies everyone. I just replaced my stock downpipe with a 3" pipe recently. Could that have caused this problem?

 

That won't cause it. Like said, gotta get those codes checked.

 

Replace your vss sensor,might solve the problem, if not ,you will be out just about 30.00 dollars ,only get it from the dealer,they seem to be better.
Jim

 

Page 19 - 25 gives a good overall explanation of the transmission input / output codes and what they mean. The last page is probably the most informative in layman's description.

http://www.motorcraftservice.com/vdi.../DOBDSM971.pdf

 

The overdrive light blinking & the hard shifts relate to a sensor that is on top of the rear end. This sensor is alot like the CPS. I've got a price quote from the local NAPA store for $15.00 for one & they even had it in stock.

I haven't replaced mine yet, but I need to. When my truck starts shifting hard I just pull over & stop & shut the truck off & then restart & the problem stops for the time being.

 

before doing ANYTHING get those codes checked, pointless to throw parts at something that may not even be broken... for example: my truck will do it if i hold 10-15 lbs of boost for more than ~10 seconds before a 4x4 launch.. once i get to the end of the track/run and try to go a steady slow mph it'll just constantly shift up HARD and lock the TC... but its just because the trans got confused from the 4x4 launch, if i let it cool down/clear codes (my gauge can clear/read codes on the fly)/give it 10 minutes, it'll go back to normal

 

Sometimes it does, most of the time it does not. The ONLY way to know is to get the codes checked.

 

exactly, just get the codes checked and then let us know what they are and people can help you through step by step

 

Sunday afternoon, my O/D light came on while going up I-5, blinking.
Got to Autozone but they picked up nothing form ODB-2 port. Disconnected the battery for a few minutes and then went on my way. I didnt drive it yesterday, but today I took it to work, and within a few miles down the road, the light started blinking. Of course the shifting hard started in again too.
I read on here get the codes-if the Autozone ODB reader won't work, then where do I get them read?
I got the diag this morning-P1728, Transmission Slip Fault. The service department didn't give me a warm fuzzie about their diagnosis (and treated my daughter poorly). They said it might be the TCC solenoid, but they want to replace the TC and overhaul the tranny ($3500). I don't have $3500--my ex has all my money. I need to be sure all the lesser cost avenues have been addressed. Feedback please?

 

Pretty much Ford or a reputable tranny shop. If the light blinks there is a code.
Ps. This thread is 5 years old.

 

Autozone can only read codes that turn on the Check Engine light. They cannot read the codes that flash the OD OFF light.

 

^^^^ AZ (et al) can't read codes on our trucks at all, whichever light is on.