O/D light Flashing

I have a 2000 Windstar 3.8 with 60K miles. When driving around town at lower speeds, no CEL and nothing flashing. But when I am on the highway driving around 60 to 70 mph, after about 5 mins, the `O/D off' light starts flashing. But I do not notice any change in speed or the engine revs. When I turn the engine off and start again, no flashing at lower speeds. Can anyone suggest what I can do.

If you look at a post further down, you'll see some possibilities.

Some have had this problem in conjuction with cruise control failure and other issues. This was the brake pressure switch issue.

Wiswind has mentioned in previous posts that a flashing o/d light can be indicative of transmission issues. usually a reputable transmission shop can help you identify the error codes.

I would get it in to have a transmission diagnosis ASAP.
A very common cause of problem is the Transmission Range Sensor, TRS, which sits on top of the transmission.
If they come up with some "indeterminate electrical code".....or "incorrect gear ratio"......I would change the TRS out.

If it is a torque converter code....then it could be something more serious and/or expensive.

Hopefully the fluid has been changed at least on the 30K mile intervals.
If not.....you might try adding some AutoRX.....drive 1K miles....and change the fluid, using a Mercon V rated fluid.....
You can get the AutoRX at www.auto-rx.com Instructions for transmission application are on the website.
You MIGHT.......get luckey and free up what is sticking (if it is the torque converter code).
Otherwise......it would likely be expensive.

Thank you for your advice guys. I will follow up on using Auto-Rx cleaning. Went to the local Autozone/Advance Auto/Napa stores. They had never heard of Auto-Rx. I am going to order through the web site.
No, I have not changed the fluid. Now I am going to do it. The actual milage is 56K. Hopefully it is not too late.
One quetion I have is that is there any harm if it take me 6 to 8 weeks to go 1K miles while Auto-Rx is in the transmission ?

Most likely not.....but I WOULD get a dignostic done ASAP........so that you have an idea of what is going on.

I had this issue after having my transmission rebuilt. It turned out that several things were "not right". Among the items replaced after the rebuild was the torque converter was found to be defective.

What caused my code was that the torque converter would fail to lock up properly at highway speeds. It did fine driving in O/D below 65 mph. It would have been a costly repair but because it was under warranty from the rebuild, it was covered.

Getting it checked by a good transmission shop as soon as possible may prevent a more costly rebuild or repair. Good luck.

My O/D light flashed on several occasions.

The first time it flashed, it would do so intermittently. I didn't do anything about it. Later I noticed a fluid leak above the front bank exhaust pipe that dripped on the pipe and caused smoking. I was on a trip at the time and was not able to get it into service, but I checked the fluid level, which had dropped significantly and then kept the level at full from that point on. A few hundred miles later the housing of the transmission failed in the area of the differential and I had to replace the entire transmission. I was on my trip at the time, too far to tow home, and got the best deal I could under the circuimstances.

After I picked the car up to return home with it, I noticed the light flashing again once I was ~ 100 miles down the road. It was intermittent again, and after a few weeks of looking and some very strange shifting patterns, I realized that the problem was due to a problem with the velocity speed sensor on the transmission (VSS). It turned out that it was not connected.

The next time I saw the flashing O/D light was when my 'new' transmission began leaking large quantities of transmission fluid from the torque converter housing. This time I was also on a trip, but "only" 150 miles from home, so I decided to pay for a tow home.

The transmission didn't leak for short trips, so I was able to top it off and drive it to a few shops for estimate of repair/rebuild of the unit. The shops found a problem with the torque converter clutch (TCC), the front seal, and several other internal components to the extent that I decided on a complete overhaul. Incidently, one of the symptoms of the TCC is an intermittent frontend vibration while cruising. I'm still trying to get that resolved, although thankfully it is still covered by a full warrenty at this point.

I believe that most OBDII scanners (such as those used at Autozone/Advance Auto) don't read transmission codes (I might be wrong about that), so you would need to visit a transmission shop or dealership to get a good reading. I visited three shops before choosing one to do my repair.