Seems to be when I'm accelerating between 30-45 mph. When I put it in Tow/Haul mode, problem goes away. Bad Tranny?

 

check the fluid. Probably either low or very old

 

Can't remember if it was someone here, or a coworker that had the same issues, but he cleaned the TB, new TPS, new IAC, new spark plugs. Issue cleared up. Sometimes throwing parts at it works.

 

If those don't fit, try seeing if one these TSBs fit what you're experiencing:

SB 18-092-15
SB 18-047-11
SB 18-066-16

I was having issues with the downshift. After the dealer flashed the PCM, it's much smoother.

 

I brought the fluid level up to normal/hot. I even used a bottle of Lucas Anti Slip. Changed the spark plugs, cleaned the intake throttle, MAS, and replaced the IPS. Still no change.

 

It throwing any codes?

 

Did you disconnect the battery and reset after all the work?

 

I don't have any check engine lights. I tried to do the ignition key method but didn't get anything.
Please explain how to do a reset by disconnecting the battery cable

 

Unhook your battery for a while and try to start it (hold 30 seconds) with the battery still not connected. This will drain any reserve power and reset your PCM. Then start your truck 3 times, leaving it running for at least a few minutes on the third time. Starting 3 times - Buckle up, start rig and let it go through its checks, then when all the dash lights go out shut it down. Wait a few seconds, then repeat. On the 3rd time, let it run for at least 5 minutes.

Leave it disconnected for 5-10 minutes, just long enough to ensure all power is drained. It might be done in one minute, but why rush it. Don't forget to hold the key in the starting position for 30 seconds while the battery is disconnected.

 

Shuddering under acceleration is usually drive shaft U-Joints (or burnt up plugs). Transmission is really tough in these trucks. Rarely an issue.

In my garage the checklist as well as the repair/replace in order would be
- spark plugs replace, NGK 2262, V-Power copper
- driveshaft u-joints replace
- transmission fluid and filter change
... if problem persists then get into replacing sensors, which would be futile and nonsensical without any error codes.