I may have found it. Gonna bring my car to the dealer with this TSB. "Launch Shudder" is the best description I can think of for my problem anyways. I notice sometimes my tranny likes to hang rpm on shifts.
A/T - 4T65E Harsh Shifts/Shudders/Slips/DTC'* Set
File In Section: 07 - Transmission/Transaxle
Bulletin No.: 0O-07-30-002B
Date: July, 2002
Slips, Harsh Upshift or Garage Shifts, Launch Shudders, Flares, Erratic Shifts and Intermittent Concerns, DTC P1811 or P0748 Set (Replace Pressure Control Solenoid Valve Assembly)
1997-1999 Buick Riviera
1997-2002 Buick Park Avenue
1998-2002 Buick LeSabre
1999-2002 Buick Regal
2000-2002 Buick Century
2002 Buick Rendezvous
1997-2001 Chevrolet Lumina
1997-2002 Chevrolet Monte Carlo
1999-2002 Chevrolet Venture
2000-2002 Chevrolet Impala
1997-1999 Oldsmobile Eighty Eight
1997-2002 Oldsmobile Silhouette
1998-2002 Oldsmobile Intrigue
2001-2002 Oldsmobile Aurora (3.5L)
1997-2002 Pontiac Bonneville, Grand Prix
1999-2002 Pontiac Transport/Montana
2001-2002 Pontiac Aztek
with Hydra-Matic 4T65-E (RPOs MN3, MN7, M15, M76)
This bulletin is being revised to add additional models and model years. Please discard Corporate Bulletin Number 00-07-30-002A (Section 07 - Transmission/Transaxle).
Some owners of the above vehicles with a HydraMatic 4T65-E transaxle may comment on harsh upshifts or harsh garage shifts, soft shifts, shudders on hard acceleration, or shifts erratic. These conditions may appear intermittently or set a DTC P1811 or P0748. During diagnosis, a low or high line pressure (actual versus desired) may be observed.
The above condition may be due to any one of the following which may affect line pressure output:
^ Sediment inside the pressure control (PC) solenoid valve, causing the PC solenoid valve to mechanically bind.
^ Sediment in the valve body, causing the torque signal regulator valve to stick.
^ Incorrect transaxle oil level.