2004 Chevy Impala Hard Shifts and trouble going into 1st fr

That's the problem. It never showed the codes at first and it doesn't show any codes now. It only showed codes after the transmission was damaged. Had it checked by several reliable mechanics.

Shifting problem is very intermittent. Happens when cold and when hot. Seems to be a harsh shift into first from dead stop only every once-in-a-while. Sometimes if feels like it didn't downshift all the way when it occurs. At times, it begins shifting hard between all geers especially with multiple stop and goes.

I have no idea if the torque converter was replaced.

I did find an old report from Firestone when engine light came on when I was on vacation in Florida. The 2 codes that came up were P0101B Mass Air Flow Sensor Performance. (They found a loose clamp at the sensor and tightened, then retested). Also had a code of P1811C Max Adapt and Long Shift Transmission code. I was about 1000 miles from home on a Sunday and this was the very fist time that any codes at all came up.

I have since researched the P1811C code and found information online from:
Section 01 - Transmission/Transaxle
Bulletin No: 00-07-30-002B
Date: July, 2002

Subject:
Slips, Harsh Upshift of Garage Shifts, Launch Shudders, Flares, Erratic Shifts and Intermittent Concerns. DTC P1811 Set (Replace Pressure Control Solenoid Valve Assembly)

This was for many GM's from 1999 - 2002.

Don't have current codes and since then many items were replaced on my vehicle.

Does the Pressure Control Solenoid Valve Assmembly get replaced as part of a new transmission?

Also, since my last post, the Temperature Gauge is going crazy maxing out at times on my display. No engine lights are ever present. Smell an electronic burning smell in trunk that wasn't there before. (I work on computers and networks for a living and know the smell very well!)

I looked up problems with Key Fob as well, since my car seems sort of "moody" and sometimes it will not lock in the mornings, but will in the afternoons. That research lead to possible PCM module problems which has also been replaced.

As of this posting, still have odd Key Fob problem, still hard shifts and slips harshly into first only intermittently. Temperature gauge goes up and down at will, but engine is not even hot to the touch!

After Speaking with my GM Mechanic about the previous post of error codes, he stated that all had been replaced, so it could not have been any of the solenoids, display panel or PCM.

Problem still persists and mechanics are unable to resolve.

What in the world could it be?