All,

I recently had the dealer perform some work on my 05 F350 V10. They replaced the emergency brake pedal as it was broken.

Since I have gotten the truck back it has been shifting differently. Most notable it seems to act (one in a while) like Tow/Haul is engaged but it was not. Yesterday while coasting down a hill the truck suddenly downshifted like it was in tow/haul (but it was not). Twice it has also done that while going down a hill when I tapped the brakes lightly. I have also noticed that it seems to not use 5th gear occasionally as well...like it is being locked out.

No CEL lights or any other indicators. Apart from this recent behavior the truck is working great. I have 36,000 miles.

Any ideas?

 

-bump-

Decided to post an update and more info hoping to trigger some thoughts from all of you smart techs.

I took it into the dealership for this shifting issue and they could not reproduce it. They charged me $129 and sent me on my way as there were no codes.

Today the problem happened again. I was doing 60 miles per hour with cruise control on and started descending a hill. The transmission downshifted like it was trying to slow me down as I was picking up a little speed. I was *NOT* on the brake. Once the hill leveled off it upshifted *VERY* hard. Bone jarring hard. It then had no overdrive. I sped up to 65MPH and it never upshifted into OD, was running about 3kRPM. I ran it like this for about 15 miles...I varied my speed from 45MPH to 70MPH and she never shifted...I then slowed down to 35 and used the shift lever to select 3rd gear. Nothing happened...then I selected 2nd gear and it shifted. I then stuck it back into "D" and resumed speed and it was shifting normally. The whole time no service engine soon light, no flashing tow haul, nothing. It is like it is what the truck wanted to do.

This problem keeps happening, but not often enough for the dealer to catch it.

Right before this happened for the first time (when I made my first post) the dealer replaced my e-brake pedal as well as doing a 4 wheel brake job. Is there anything they could have busted in that process to cause this? It seems all too coincidental.

It seems to be a sensor problem because it shifts beautifully, but I am not sure. It feels like the truck gets confused

The problem almost always involves a hill that I am going down at the time.

I was thinking possibly the VSS, as I had to replace it a couple of years ago, but I am not getting any ABS light or speedo problems...

Are there any other sensors I should look at? I feel marooned here as the dealership has provided no help and only takes my money.

Thanks in advance for any ideas you smart guys have. This is a weird one.

 

Very interesting...

When the symptoms start to occur see if your cruise control works. I'm not sure what is affected by the brake pedal switch but I know on the older trucks it would unlock the torque converter. Almost sounds like whatever they did is causing the brake pedal switch to stick intermittently which would be causing your problems. If it's the brake switch your cruise won't work because your truck will think you're trying to use the brakes.

This could potentially be a serious safety problem because if I'm right your brake lights may be stuck on for quite awhile even though you aren't using the brakes.

Another thing to check would be as soon as you see symptoms stop the truck immediately and get out to see if your brake lights are on.

 

Crazy001,

Great thought, but I do not think that is it. Cruise control will stay on when this is happening.

To shut off cruise control I often lightly tap the brake. Often this problem seems to be triggered by doing that. I tap the brake lightly and the truck will downshift and then often stay out of 5th gear from that point on. It does this whether or not in Tow-Haul. I want to make that clear as I know Tow-Haul will do a downshift for you when you are trying to stop to use engine braking.

Thanks for the idea though, please keep thinking. I am at a total loss.
---Aaron

 

Maybe Mark will chime in with his thoughts. Wonder if it is a programming issue, or if a reflash would cure the issue?

 

Senix,

Yes, Mark certainly knows his stuff.

When the dealership couldn't find anything wrong they did flash it as they said there was a newer revision. I was hoping that was it, but it did not help as it still does it.

The problem is that on a 300 mile trip it may do this once or twice. Since no codes are thrown and it doesn't happen for the 15 minutes that the dealership technician spends driving it, they are unable to find the problem.

---Aaron

 

My 2010 F250 downshifts to slow me down when descending a hill w/ cruise on also, I assumed that was just the way Fords were, my truck did it with less than 100 miles on it,

 

Your cruise is trying to maintain a constant speed, it wouldn't surprise me if it were downshifting for this reason. The OP is stating that he's having trouble after he disconnects his cruise rather than while the cruise is engaged.

Honestly the only way you can determine this type of problem without shooting in the dark is to have a full featured scan tool connected and recording data during the problem. Something that can see what the PCM sees and thus interpret what's causing the erratic behavior. I can state with some confidence that the 5R110 transmission is electronic and all shifting is controlled by the PCM. Therefore if the transmission was doing something the PCM wasn't telling it to you WOULD have a trouble code.

Therefore we can safely assume that your PCM is commanding this erratic behavior. It wouldn't do that without a reason, so our goal now is to find that reason!

I'll keep thinking on this one...

 

I am leaning towards a TCM issue. PCM talks to TCM. Just hasn't been enough for that wrench light to come on.

What do u think Tom?

 

Interesting thought, Scott. Not really sure the role of the TCM as opposed to the PCM. I read through THIS THREAD and tried to find some info about this. Really great stuff with LOTS of info, I recommend everyone here read it.

First of all:

So it appears that the brake pedal does nothing other than unlock the torque converter while driving. However...

So it appears that the PCM controls all of these functions, and it lists which factors are used. Something wonky is going on with one of the factors the PCM relies on to control the transmission.

The only thing near the e-brake other than the break pedal position sensor would be the accelerator position sensor. Since you also happen to have an electronic engine and have not had a Toyota(runaway!) event this is not likely the culprit.

I'm stumped.

 

What may have occurred is that the dealership disconnected your battery while working on your vehicle. If that did happen, your transmission lost it's map of how and where to shift for your driving style.

Search for Torqshift relearn strategy in this forum. There is a procedure to remap the transmission shift map.

 

OK, found it for you:

Torqshift Shift Relearning Strategy

TorqShift Harsh/Slipping Engagements, Upshifts, and/or Downshifts:

If these symptoms are experienced after the batteries have been disconnected, then it is due to the transmission adaptive strategy being cleared from the computer. This may occur when the vehicle is delivered new from the factory as well.

1. Warm the engine and transmission to operating temperature with all accessories off.
2. Idle engine for one minute with engine warm and all accessories off.
3. Idle engine for one minute with A/C on.
Then:
4. While driving, perform three series of upshifts at light, medium and heavy throttle.
5. While stopped, perform three sets of gear engagements (N-R, N-D, D-R, R-D) with the brake pedal firmly depressed and waiting three seconds between each engagement.

Perform these steps once in normal mode and once in tow/haul.

 

pto wires are near the e-brake pedal... possibility?

 

I thought about suggesting that to the op, but it appeared to me that he has driven the truck enough that it would have relearned, but this is worth a try.

 

Redford,

Thanks for the idea. I do not believe they disconnected my battery when they did that work because my Alpine radio did not lose the time or my radio presets. It always loses both when my battery is disconnected, even for a few seconds.

I have put approximately 1,000 miles on the truck since that brake job & e-brake pedal replacement.

Do you think I should attempt the above listed re-learn procedure anyways?

---Aaron