Question for you smart guys.... I have a 2006 5.4 SCAB with approx. 125k miles on it. Some time ago, I started noticing that when the truck is in overdrive, if the speed and RPMs are really low (around 40-45mph) and I get on the accelerator, I get a "bump"/"slip"/"misfire" from the rear end. In general the tranny seems like it's not downshifting like it should when at low RPMs.

This has only been an issue in overdrive until it did it towing my utility trailer last week......also did it in 4th gear.

I should note that I have a programmer on the vehicle that has given me a number of issues over the years. I've had the computer set back to stock for a long time, but I'm not convinced that the programmer may have done something to cause this problem.

ANY and ALL comments/thoughts are appreciated!!!!

 

Sounds more like a low grade misfire to me. How many miles on the spark plugs?

 

I've been experiencing some of those same issues in my 05 for the past year. Had a programmer on it in tow mode all last summer and seemed better until lately. I set it back to stock a few months back and it is now worse than before. Like you I am not sure that maybe it caused some damage to the transmission.

Mine doesn't seem like an engine issue with only 75K miles and new plugs, fuel filter etc. all within the past six months. The new thing I have noticed is that when it sits for a few days (garaged) and I start it, you can hear what sounds like a dry power steering pump noise coming from the center console - goes away after you drive it a block. It's always done it when sitting outside with super cold temps but seems to be getting more consistent.

Good luck and let us know if you get it diagnosed...

 

Plugs were replaced about 3 years or 45k miles ago.

 

If I'm running overdrive on the interstate, I basically have to let off and get back on the accelerator to "force" a down shift. Only way to eiliminate the issue. If I let the RPMs drop too much, the issue repeats itself.

 

See if you can force a CEL by keeping it shuddering. Then you can read the codes.

With 45k on the plugs, as long as they are Motorcraft it's a tossup whether that's the problem. It could be one or more coils starting to go out.

 

Thanks for the response!!!