When I'm cruising down the road (not pressing on the gas pedal) the vehicle drives fine but the moment I press on the gas pedal to slowly accelerate the truck starts to vibrate and the tone of the exhaust changes and gets a little deeper. Only way to make it stop is to press harder on the gas pedal. The truck does not hesitate on hard accelerations but only seems to do it when I'm gentle with it. The truck also starts to vibrate when driving down the road and keeping the truck at a speed limit of like 40mph. The truck will always vibrate between the speeds of 15mph-80mph.(haven't gone faster than 80mph) If I put the gear shifter in M5 the truck will drive perfectly fine which is weird. Also the truck will have more of an aggressive vibration when its set in 4wd. What could possibly be the problem? I changed the spark plugs and wires, transmission was changed 50,000 miles ago and I recently took the truck to the dealer but the dealer could not identify the problem. The dealer replaced the torque converter a few days ago but that wasn't it either. The truck has 251,000 miles.

 

mil light on?
torque convertor clutch shudder does seem to match the symptoms. Is that why it was replaced? wondering if m5 shuts off the tcc lock up. Wondering if you can disconnect the tcc solenoid and test drive to see if the problem is gone. Any tcc fuse in the fuse box. if yes...pull the fuse.

 

If I understand your description correctly,,,,,,,,,,,,,,, It sounds like your vehicle is losing power under load .
Of course if you place it in a lower gear the RPM goes up and it has no power problem,, Does this sound correct to you?

 

No mil light at all. The dealer said that the torque converter is bad and needs to be replaced. The dealer replaced the tc but still has the same issue. I did a little research and tests and noticed when disable afm/forced the truck to stay in v8 the truck does not act up the way it does.

 

well actually this only happens when there's no load on the vehicle. Only happens when I'm real gentle with the pedal. I haven't tried placing in a lower gear to increase rpms to test it. I tried putting it in M5 instead of D and drove Like and it was fine. I've noticed that the problem only occurs when it's about 1400 rpms or lower.

 

When you put the trans in M5 it will disable the AFM/DOD
There seems to be an issue with the engine going into AFM/DOD when it shouldn’t

or, you simply have a failed lifter…