Stever39

Random, have you had the TSB done for the 4th to 5th and vice versa shift issue? I have had some issues driving around 25-30 and the tranny shifting from 4th to 5th. Wonder if that might be linked since there are so many people who don't have the stop shudder/stumble issue

DignifiedDevin

I have not, not that I know of anyway. I doubt they did and TSB work on the truck when it was sitting on the lot. Where can I find more info on this?

Stever39

https://www.f150forum.com/f118/trans...eflash-319486/

Stever39

That doesn't have everything but gives symptoms. Mine gets bad in rush hour traffic or on the side street by my house trying to keep 25mph

DignifiedDevin

Im not sure if my truck build date was before of after that, Id have to check. If the fix came out in September of 2015 there is a very small window that 2016's were affected.

CeeDee

I haven't heard much on this lately. Just wondering if the problems went away, got solved, or just more tolerable these days ...?

I've been filling up with premium at every fill up for the past month or so... trying to see if it makes a difference. I'm in the cooler, wetter winter months where I'm at, so I don't know if that makes a difference either.

DignifiedDevin

Sorry CeeDee,
I got the full report back from the dealer over the last visit, and they decided to replace the fuel tank. This did not fix the problem but the rumble is also not as bad. It's now much harder for me to replicate the issue as well. The problem now is, I don't know if it was the fuel tank, or something else like maybe something was loose that the mechanic may have tightened when installing the new tank.

So my newest possible theory is with the design of the fuel tank. There is a front "pocket" in the tank (which I marked with the arrow in the picture provided) and from all I've seen in pictures, there is no vent line back to the main section of the tank to give relief when fuel is fills that area and is then removed. Most old tanks that had a pocket like this had vent lines to not cause a vacuum effect. Now under normal conditions I can see that with such a small pocket there would be no need for a vent line, but because this only happens when I come to a stop and only when fuel is 3/4 full, I can see this creating a vacuum and forcing air to push by the fuel to fill that void. That air forcing itself back would create that same turbulence effect you get when you flip a quart of oil over to quickly.
Kinda makes sense no?

2015rubyFX4

I've learned to live with it. Its really not that bad anyway

DignifiedDevin

Yeah it used to be at least 5x worse then it is now. As long as it doesn't get progressively worse than I can tolerate it.

2015rubyFX4

I have to really concentrate to feel it most of the time actually so its not bad at all