I have a 2001 F-150 with what I believe to be the 4R70W transmission. It's a 4 speed automatic with the 4.6L engine.
The past two times I have driven it I have gotten a massive shaking and stuttering from the drivetrain. Each time it happens after accelerating when trying to maintain speed going uphill. Just beforehand the engine RPMs drop down, which I presume is the torque converter lockup attempting to engage.
Even though the truck is stuttering, the engine maintains speed just fine.
If I accelerate, the stuttering stops immediately.
Could something be preventing the torque converter from locking up? Or is there another possible cause of this? The transmission has 285,000 miles on it.