First a little background on my truck. I have a 2000 excrusion 7.3 basically factory besides bigger exhuast, cold air and bullydog with a 120000 miles. Truck has always shifted fine untill today. After driving for about five minutes i stopped at a light and when i took off truck wouldn't shift from first to second. However, if i manually shifted from Drive to 2nd it would shift and then if i put it back into drive it would continue to shift through all of the gears like normal. I also noticed once it was in overdrive it didn't want to downshift. I tried putting the programming back to factory but no change. However, after I let the truck cool down I went and drove and it shifted normally. I checked the fluid and its perfect. I changed the filter and fluid 20,000 miles ago and it didn't look bad then either. Any suggestions would be greatly appreciated.

 

Did you get the OD light blinking at you? If so, its stored a code. That code might help determine the problem.

 

No overdrive light blinking. I drove the truck to work again this morning and it shifted fine for about ten miles of stop and go traffic.

 

I've seen post like this before and hopefully MARK, our trans expert will chime in on this. I have seen him post that not shifting from 1st to 2nd is a sign that the trans need a rebuild. I don't know this, but I have read his answers in lots of post.

I hope it's something simple. Good luck.

 

It could have been just a sticking valve. If there is some sort of debris in there causing the sticking, then it could be a sign of future problems. I had the the bearing go out in the center support housing of my trans and some metal flakes caused some similar problems all of a sudden. The shifts came back, but didn't feel right. I did, however, find some metal in my pan during the previous trans service. Nothing showed on the stick. I, later, found the problem when I tore it down.

 

BUMP, I need help

 

Is it acting up again?

 

That's true for a 2001 truck with a mechanical diode. It wasn't in the 2000 trucks.

I can only guess. My guess is that a valve stuck and is now free. If it doesn't do it again I don't think we will ever know why it happened.

 

I have been reading through various messages all night, regarding the shifting problems from 1st to 2nd. I have a 2001 F250 SD with 108K. Same thing as so many other postings, out of the blue, my tranny started having fits... mainly it doesn't want to shift out of first, unless I get up to a good speed and let off the pedal. I have had a service engine light on for a while now. Living over 3 hours away from a Ford dealer, or any good mechanic, for that matter, sucks. I had the tranny fluid flushed and replaced less than 10K ago. The fluid levels are good and color is good. At one point, months ago, I did also have an ABS light coming on at times. My main question sis this: A couple of people claim that the VSS, (speed sensor?), on the rear differential should be the first and cheapest start to some of these problems. O'Reilly sells a couple of them for under $20. I did have a shop last year check all my ABS related stuff and all looked okay. They also said to change out that sensor to see if the ABS light goes away. Could something that simple cause or fix such issues as this? I have to admit, I seriously doubt I have ever had the filter changed.

 

There are four things common to a VSS getting flakey or inop:

Speedometer gets erratic.

Shift points get erratic.

ABS light comes on.

Cruise control won't engage, or disengages without any action by you.

Do you have the other symptoms, too?

Pop

 

I have never seen my speedometer get goofy and the only issue I have ever had with the cruise, is some slight "bucking" when going downhill. I have had ABS light issues on and off for about a year now. I have not seen that light come on for over a month now. Tomorrow, could be a different story, however.

So is the mentioned VSS in other posts, the same as the ABS speed sensor on the rear differential?

Other symptoms? As far as the tranny doing strange things in just the past week, it also seems to want to downshift, all the way down to 1st, from 3rd or 4th, when I tromp on it. Not a good thing.

 

Yes, the "ABS sensor" is, in reality, the Vehicle Speed Sensor (VSS).

I wonder if you are developing a sticky line-pressure modulator valve in the accumulator body. That can happen at your mileage.

Pop

 

Thanks for all the help, Pop. I am paying attention to everything I read. I am in no position to spend thousands on a rebuild. I have had this truck since day one... taken very good care of it and never had any major problems. Very few minor problems at that. One more question. I have read that their are or is, (could be depending on the manufacture date), a mechanical diode(s) in my transmission? I hope I read that right. What the heck is that all about?

 

Pop, does the vss need to be a dealer item or is it something that can be gotten at the chain stores?

I know the CPS from the chain stores are unreliable, but not sure about the vss.

 

A mechanical diode is the brand name for a type of one way clutch. Every ride a 10 speed bike? The part that lets you coast without pedaling but catches as soon as you pedal faster than the wheel is turning is a one way clutch.

Mechanical diodes clutches were installed in the 4R100 at the start of the 2001 model year. Supposedly all the trucks with gas engines had their transmissions replaced with non-mechanical diode transmissions before leaving the assembly plant. I've heard stories that not every truck was caught.

Diesel trucks kept the mechanical diode from the start of the 2001 model year until March, 2001.

If you have a mechanical diode when it starts to fail the symptoms are that the trans won't shift 1-2 until high RPM, and then only after you let off the go pedal.