I have a 2001 4x4 F-250 with a 7.3L PSD and a automatic trans. I keep getting a flashing overdrive light and my truck seems to shift harder. Today on my way from kalamazoo to belleville (approx. 2 hr. drive) I had the light flash for about 10 min then shut off. I noticed when I shut my truck off I dont have any problems for a little bit. Last week I changed the sensor on the rear axle thinking that it would solve my problem. My truck also is equipped with a TruSpeed. I completly unplugged that thinking that was causing my problems because also My speedometer would jump and my odometer will cut out every once and awhile. I plugged in my code scanner and I could not come up with any trouble codes. Im not sure if there are any other sensors that could cause this. Any help is appreciated, I am trying to avoid going to the dealer and avoid paying the big $$$.

Thanks,
Derek

 

sounds like your sensor on your rear diff needs to be replaced. reads your speedo gear and makes your od light blink when bad.

 

Its the sensor on top of the rear axle right? The VSS. I already replaced that and that didn't change anything.... so im not sure what could be causing this....

 

You changed the sensor on the rear so it may not be the sensor. Might check the plug to be sure it is seated well. Does the fluid smell and look good?

 

i actually just put in some amsoil synthetic about a month ago...

 

I found out a while back that there are lots of things that have input to the OD off light flashing. I went to the shop where I ALWAYS take all my vehicles when they need major work...and told them that it might be the VSS on the rearend...(like I knew what I was doing) ...and he told me that there were over 20 different things that would cause this....from slipping tourque converter to engine issues. Well I questioned the engine issues and he said some things would cause that insted of the SES light. Well they called me back and said that it indicated low fuel pressure. They put a mechanical gauge in the fuel line and noticed that the flow rate and pressure were on the lower limits at idle and while normal driving. When I got the light, I was pulling 9500 pound fifth wheel through the mountains. They suspected clogged fuel pickup screen or some trash in the tank. Well I ordered the ITP diesel in tank pre pump kit along with the HPX high pressure crossover lines and they installed everything. The did find some trash in the pickup screen ( from the truck stop where I last got fuel) and they were right on with this diagnosis. I picked it up on a tuesday, and wednesday took off out of Charleston to Toledo Ohio with the same camper through the mountains. 2000 miles later, the engine is quiter, and the flashing OD off light has not come back...(knock on wood )...so to make the long story short, there are lots of things that can cause it, but the VSS that you changed is the most common and cheapest place to start, so on to the next thing, whatever it may be....just my1.5 cents worth...sometimes it aint even worth 2 cents.

 

I had the "OD" flashing light about a month ago and it pulled a code for the speed sensor.

See if you can find an FTE member who lives close to you who has a code reader.

 

As Somkin & Dave said get somewhere and get it scaned. Flashing OD lite is your transmission telling you there is a problem and I need attention. IT could be anything from overtemp to VSS to Tc lockup failur.....Good Luck

 

Thanks for everyones help... I really appreciate it!

 

the guy i bought my truck from said he had that happen to him and the OD would not engage and i tore up something in the tranny and had to replace the tranny
there is a sensor in the shift **** that i would try to replace or check
it is mentioned in the haynes manualv on how to replace

 

Check your fluid. low fluid can make the tranny shift funny and throw a light.

 

My fluid level is normal and it appears to look good.... so far i have had no problems with it shifting in and out of overdrive even when the light is flashing, the only thing is it shifts harder when the light is flashing....

 

It's trying to tell you that something is wrong. If you don't find someone SOON that can read the code that's stored and fix what's wrong you will probably need a new transmission. If you fix it SOON you might only need a sensor, or need to fix a broken wire.

 

I took my truck in and all that was needed was a reset for the computer. Thanks for everyones help.... I really appreciate it!

 

This is the "good kind" of thread. Guy has a problem, people jump in with their "fixes", and he comes back with the solution.

Now everyone has another fix to remember.