I'm having some driveline issues hope someone else has had some experience with this too. I've got an 03 fx4 5.4 AT with the 9.75 rearend. While driving theres a jerking slipping feeling but its only happens at very low rpms and under load just before it downshifts. Its most noticable around 50mph when it downshifts into overdrive and drops to around 1300rpm. When I accelerate (just barely, sometimes i don't even have to accelerate) the truck jerks or lurches like something is slipping. I originally thought a tranny issue since it only seemed to have trouble with overdrive but tonight i noticed the same issue making it up a steep hill at my friends house. It did the same jerking just before shifting down to first. I'm possibly thinking torque converter or something with the rear end. The 100,000 miles previously owned my truck was used for work by a remodeler and before that a landscaper but was always serviced at ford. I've currently got 110,000 miles and the tranny still is tight, making firm quick shifts with no slippedge otherwise. Really kinda lost so any advice would be appreciated. Sorry for the long post but thought I'd cover everything. Thanks a lot.

 

My 02 4.2l was doin something similar mine was always jerking and slipping feel sort of like it was tranny between 50-60 mph. Before or after 50-60 no problems. If this is ur case too I changes wires and plugs and no probs since. Just an idea. It worked for me. Hope this helps. I was also thinking it was the tranny too.

 

(1) MAF sensor (2) MLP sensor. A MAF sensor going out will often cause inexplicable lurching caused by the engine momentarily shutting down then coming back to life. I know of no way to test the MAF except to temporarily replace it with a known-good unit.

The MLP sensor tells the PCM what gear in the tranny is engaged. If the resistor chain contacts inside the sensor get dirty, the connector is loose or dirty or the sensor is mis-set, then a bad signal is returned to the PCM. Often when in OD the tranny will try to shift to 3rd....not good.

 

To test a MAF sensor take a screwdriver and use the but end of it and tap on it when it starts acting up if the problem goes away you found the culprit if not you didn't spend any money

 

It already has new plugs. And as for the sensors, I'm pretty much lost when it comes to sensors and electronics so I'll have to have someone look into that. Thanks for the advice