I have a 2002 F150, 82K, 5.4, (auto 4r70w trans). I've owned the truck about a month and have put a couple hundred miles on it. It's not my DD. Prior to today it was last driven just over a week ago. It has run like a champ and no problems prior to today. Today would be the furthest I've driving at one time.

Fast forward to today. I drove an hour north on the highway doing roughly 75MPH to pickup some nerf bars for my truck. Truck ran fine. On the way home however she started acting funny. I noticed as we started moving on the way (doing maybe 20MPH) home it felt like a pulsing-jerking feeling. The feeling you might feel if your back wheels slip on ice for a split second. It's 60 here today but rainy so I figured maybe the tire slipped on the wet road. Well, when we got on the highway it got worse. Anytime I put the truck under load (accelerating or moving from level ground to an incline) the pulsing, slipping feeling we would feel in the truck. I couldn't accelerate as fast cause it felt like slipping. The engine sounded normal. The RPM's did not increase nor did it sound bogged down when it slipped nor did it sound like a misfire. When it started the stumbling I would let off the gas and try to baby as much as I could. The more you babied it the less likely you were to feel it stumble. But if I tried to accelerate too much we would feel the slipping.

I stopped on the side of the road to check the fluid level and it was fine. The fluid looked a healthy red and did not smell burnt. A few weeks ago I did the trucks first tranny drain and refill. I know it was the first time it was ever done because the dipstick plug was still in the bottom of the pan. I replaced the trans filter with a Puralator and used Castrol Mercon V trans fluid to top it off. And FYI I also replaced the fuel filter (Motorcraft), changed the oil, replaced the air filter and did the Gotts mod, flushed the coolant, and changed the transfer case fluid.

Right now I'm letting the truck completely cool and going to see if it still has the slipping feeling when it cools down.

I pulled the codes using the key on and plugged into the reader but it reported no codes.

Any guesses?

 

Hmmm.....Might be the transmission. Might also be a (going) bad coil- on-plug... The 2 vehicles I have (01 F150 w/5.4, 06 Explorer w/4.6) both had me thinking transmission when a COP went bad...

 

It could also be the torque converter not staying locked. Sometimes, tapping the brake pedal will lock the converter.

If it's a COP, you may have to force the code to trip by not letting off the gas. Eventually you should get a misfire code.

I had a low cost scan tool once that wouldn't read transmission codes ?

I had similar issues in a '99 with the 4.6, and that time it was the converter. Since though, on 3 other Ford engines, it was a COP.

Dave