We had a rebuilt 5.7 put in it after the valves seats catastrophically failed.
Seemed okay but lots of new sensors needed, etc.
The guy "flashed" it to '07 software, not sure if that was good or not.
Recently it started having a shudder between 1300-2000 rpm.
At first it was noticeable under load like going up the mountain but it does it sometimes on the flat highway as well.
Above 2k rpm it seems to go away.
It's extremely intermittent.
Sometimes it does, sometimes it's fine.
Dropping it into "4" only helps a bit and "3" is a bit better but that's not exactly great for interstates.
We changed the tranny fluid, installed new Champion copper plugs, had the tires checked and the mechanic said the drive shaft and u joint seem fine.
He was not able to see the torque converter without a tear down.
It's not throwing any codes, with the key dance or the EVIC.
In 2017 I was slammed from the rear by an uninsured driver and insurance fixed the body damage, rear struts and straightened the frame.
But it's seems to feel like the transmission is "weird" since then, shifting when I think it shouldn't yet, etc.
I'm sorry I can't explain this in a more technical way buy I'm just the wife, here and don't know the terms.
Any ideas?