Ive got a 2006 5.4, Fx4, screw, with 90,000 miles.

Recently it shifts perfect except when it down shifts from 4th gear to 3rd gear. If i mash the pedal it is fine, its only when it just a slight accerlation and it is a easy down shift that causes the problem. What it does is almost like it wont lock into the gear, it bucks lightly but where I can feel it still. Im going 40 to 60 mph when this happens most of the time.

Im not sure if there is a sensor of something else that would be the cause this of is maybe my Transmission is just shootin craps. Also, i have a SCT tuner that i havent hooked up to the truck yet, but do you think if i pluged it in and turned up the shift firmness if it would help.

Thanks for any Input.

 

Did you figure out anything on this? Mine is doing the same thing.

 

When was the last transmission service? Most the time changing the fluid and filter will stop these issues. Hope you get it solved!

On another note I have a tuner and bumped up the shift firmness by 1 point and now my truck shifts like my old car with a shift kit and modified valve-body. The tuners really help the transmission shift better but due fluid and filter before anything else.