I am hoping someone here can help me AND my mechanic with a strange problem I've been having with my van for several years. The reason for "several years" is that I CANNOT *MAKE* it happen...it just happens when it feels like it!

Here's how it usually plays out:
I'm driving with cruise control on (doesn't have to be on, but often is)
The cruise control cuts out
The overdrive light on the shifter starts blinking (not always, but usually)
The transmission has great difficulty shifting up or down...it makes a roaring sound, then BANGS into gear. Sometimes it feels like it's slipping gears. This happens both when speeding up and slowing down
If I keep driving - carefully - it goes away, and when it does the overdrive light goes out (if it was blinking) and the cruise control comes back and can be set again

When it happens and I'm not actually using the cruise control, I can't use it until it all clears up at the same time.

I just had a new transmission put in the van (burned up my previous one on a mountain), but the problem still occurs. My mechanic did find a speed sensor that was not registering properly and replaced it. He also found that the (darn can't remember the exact name) - but a sensor that tells the transmission where to shift was off by 1 tooth.

The last time I brought the van home, when they thought they had found the problem, I drove it from North Georgia to South Carolina (about 100 miles), using cruise control almost the whole way, with no problems at all. Then I drove it on short trips all the next day with no problems. Then I drove it to work (about 30 miles) with no problem. But when I left work, I didn't even get out of the parking lot and the transmission started shifting rough and the overdrive light came on. When I got to the highway, the cruise control would not work.

So I drove to my mechanic's shop (about 30 miles) and the problem was so bad I was afraid I wouldn't even get there...but about 10 miles away, it all went away. I've NEVER been able to get it to happen for my mechanic!

It doesn't seem to matter if the transmission and/or engine is hot or cold. I once drove it from Georgia to Massachusetts with no trouble at all, but on the trip home the cruise control cut out in Virginia, the overdrive light started blinking, and the transmission shifted rough. Then, about an hour later, it all cleared up and I drove all the way to Georgia with no problems.

On the other hand, I've had it start before I even got out of my driveway, which is VERY short!

I'm sure stumped (don't know much about automatic transmissions anyway) and my mechanic is stumped too. Whatever it is I don't see how it can be the transmission itself, since the problem is still there after installing a new transmission. I'm thinking it's got to be some kind of controller...but what controller I have no idea.

ANY suggestions?

 

Yes, I have a suggestion.

When the OD OFF light flashed one or more error codes are stored in the computer. With the codes I can make an educated guess at what's wrong. Without the codes all you can do is buy parts, throw them on, and hope for the best. Once the codes are stored they will remain in the computer's memory for about a month after the last time the light flashed. If a mechanic tells you they can't read the codes because because the light isn't flashing find a better mechanic.

 

Sounds like the signal from the PSOM to the computer is going and coming.
The error code in the computer I am sure is about the VSS but I dough that is the problem as the VSS sensor very seldom goes bad but it gets changed out a lot.

If I were to guess it sounds like a broken solder joint on the PSOM board or in the PSOM plug.

I say all of the above because you never said anything about the ABS lamp flashing on the cluster.

 

Thanks! No, the ABS light never flashes...only the overdrive light on the shift handle. Nothing on the instrument cluster ever looks odd. Gauges all normal, no error lights, no check engine light. I'll get with my mechanic about the PSOM...that's not something that's ever been mentioned before.

I also called my mechanic and he's going to see if he can get the codes, but that's probably iffy. It might come down to me having to bring the van home and drive it until the problem happens again, then getting it to him so he can pull them as close as possible to the event. We'll see how that plays out.

 

Is your speedometer steady or does jump some when this happens?

 

"Is your speedometer steady or does jump some when this happens? "

It's funny you posted this question, because I *just* thought of something I had forgotten because it hasn't happened in quite a while...but a few times last year the speedometer did jump around, gittering back and forth and sometimes pegging out at either the highest or lowest spot. I know it hasn't happened lately though, because what attracted my attention when it DID happen was that it made a distinct clicking sound when it was jumping around.

 

The transmission control from the PCM Computer, the Speed Control (you call it cruise control), Odometer and the Speedometer all depend on the information from the PSOM to do their job.

If it is not the PSOM then it is the wiring from the rear end VSS (rear axle speed sensor) to the PSOM, VSS or bad bearings/exciter ring in the rear end.



VSS: Vehicle Speed Sensor (rear axle speed sensor).
PSOM: Programmable Speedometer/Odometer Module.
PCM: Powertrain Control Module.

The PSOM:


The PSOM location:


The PSOM shown plugged into the speedometer head:




/

 

Sounds like the old "speedometer guage cluster is going south" thing. My 95 did the same thing. Dealer replaced the cluster and it was fine.

 

Another cluster could also be had from eBay for less than $100 I'm sure.

Its also possible to find a NOS part there too---same affordable prices if so!

 

I'm a bit puzzled about the instrument cluster post...are you saying something could be wrong with the instruments and THAT is causing the problems with my transmission and cruise control?

 

Yes that is more than likely what is causing your transmission problems and speed control problems. Yes the cluster but it is the PSOM inside that is the problem. You can get a cluster from a 1992-1996 F or E series and take the PSOM out of it and put the PSOM in your cluster.
If you go to a salvage yard you may want to get two or three clusters to make sure you get a good PSOM. Some of the trucks and vans in the salvage yard may be there because they have a bad PSOM in them.
I do not think you can buy a PSOM from a Ford dealer any more and if you can it would be over $400.00 to have them put it in as they will not let you do it.

Note that if you get a PSOM from a truck or van in a salvage yard it will have the mileage on it that the truck or van had on it. The same goes for ebay.
You may also have to change the tire size in the PSOM to make the transmission shift right and the speedometer to read right.

Note also that you are wrongly calling the Speed Control, "cruise control".

 

Thanks for the additional information! I'm learning a lot I didn't know before!

"Note also that you are wrongly calling the Speed Control, "cruise control". "

Well....you knew what I meant, didn't you?!

 

Yes I knew what you meant but if you are going to look up this system in Ford diagrams and Ford shop manuals it is called Speed Control in them. It was just a heads up for you.

Also I edited the above post so you might want to re-read the post.

 

Here is the diagrams of your speed control.





/

 

Latest update: I went to my mechanic to pick up the van so I could bring it home and take some things out of it. I didn't even get out of the parking lot and it shifted rough. Then it smoothed out...so I kept driving and it came back, worse, and the overdrive light blinked...then went out...then blinked again and went out again. I turned around immediately and took it back. They pulled the codes, but said the only one was 111.

But this is something of a "breakthrough" because I have NEVER had it happen so close to the mechanic before!