What actually was wrong with it?  thanks.

While going at speeds of 50-70 mph it felt as though the trailer brakes were coming on and causing the truck to jerk, sometimes very severely.  But it didn't do it ALL the time.  It was a pulling back, porpoising, jerking motion.,  It was not the road surface causing it either--it did it on new asphalt.  So we began by looking at possible electrical issues--to which none were found.  We only pulled one tire to see if it were a mechanical issue--everything looked great.  So we took it to Ford and they checked out thecomputer system on the truck--which tested normal--but when they put in a symptom check for 'buck and jerk'  they got some matches--and Ford had a download to update the computer.  So, problem solved??  Hope so.  Before I am thoroughly convinced I'll have to put more tow miles on it.  Thanks for the interest.

I understood him to say that it was an error in the computer system that was not picked up by a general scan, but that showed up when the diagnostic equipment was given more information.  The diagnotic equipment suggested that there be a computer upload or patch to remedy the problem.  (If this is incorrect, please correct me.)

This is quite interesting to me.  My 2005 6.0 always runs with a precision that is just beautiful for about two to three days after it's connected to one of those diagnositc computers.  The fuel mileage goes up about 4 mpg and it runs very smoothly.  Then it goes back to the way it was before - which is "fine" but not that optimum performance. 

So, I hope this is a permanent fix for your problem. Thanks for the information. Very interesting.

So let me get this right.  Not to be sarcastic but..  The computer had some kind of electrical problem or wasn't reading something right then?   (Vaporlocked)  ha.

Funny it didn't just shut it's self down or go into a limp mode.

Perhaps I should have let the op answer, but I didn't so....

You probably know more about these trucks than I - ask the dealer who sold it to me and said it would run when it wouldn't lol.  But, are you saying that any of the computer problems will result in a complete shutdown  - ie "limp mode"?

Can you explain why you think that a computer error wouldn't create the symptoms described in the original post ( or in mine for that matter - never have understood the consistent improvement after it goes on that diagnostic machine, though one mechanic said it caused a reset of the computer, but that the computer soon defaulted to the original performance). 

I'm interested because my truck *may* exhibit the same symptom - very slight but it does "something" that I'm trying to figure out.

You nailed it!  Our 2001 F-450 diesel dually has not had any other issues and really the jury is still out on this because I have only put 20 miles on it hauling.  I hope this does take care of the problem, however! 

Hope you get your truck issue resolved.  Thanks.

Thanks. I hope your issue is resloved.  My truck has actually been a very good one since the initial disasterous first few months after purchase.  I'm pretty good at assessing its performance, though, and it's not at its usually 95 percent (100 percent being those initial two or three days after it's connected to the diagnostics).  I'm doing a few things to see if I can figure it out.  Most Ford dealers around here can't tell if a truck won't run, much less more subtle changes.  Maybe that won't be true now that it's not under warranty! lol 

I hate Ford.............

Oh, aside from the initial stuff with our 6.0 it's been great - knock on wood.  The initial problems wouldn't have necessarily been serious problems (well, the usual 6.0 stuff plus an injector) had the Ford dealerships and Ford Motor Company not been so bad.  Had it not been for a small dealership in the Colorado mountains -Silverthorne, Colorado - my truck still wouldn't be running and the selling dealer and Ford would still be saying "lol ... YOU bought it. It's YOUR problem not ours."  And that's a quote by the way, when my truck was two weeks old.....It cost me hundreds of dollars in rental fees and stranded me, and I couldn't tow anything with it for a long, long time, but none of that needed to have happened if the dealer OR Ford cared even the slightest. 

Right now it's like a horse that is not quite right, but isn't lame :) so maybe Silverthorne could possibly fix it, but I don't think any other dealer could.  I'll do a few things first to see if they work. I do concede that at the moment, it's subtle enough most wouldn't notice it - and I might be driven to violence if another Ford dealer condescends to me and says "now, now, you are just imagining things again - that tow truck there is only in your imagination"  lol.  Yeah, lol I hate Ford.  Shame too, I love the number pad on the door and that, in itself, would probably get me to buy another Ford. No new Fords for me ever.

It has a lot more miles than yours.  

You were really treated poorly by that dealer AND Ford--shame on them.  I agree; if I were you I would not be inclined to buy another Ford.  Are ya listening Ford?You should care.  As for the dealer...they'll have to look further away for their repeat business.  Just a idea; try pursuing resolution under 'lemon law'.

I probably should have, but I didn't and all that happened when the truck was new, before the lawsuit between Ford and International. 

Ford did a similar thing - to a much lesser degree - with a new Ford minivan I had bought so iit is their way of doing business.