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Discussion Starter · #1 ·
2003 Impala police package with 101,000 miles is experiencing an occasional delay when shifting from reverse (R) to automatic overdrive (D).

Driver states that occasionally a period of approximately 2 to 3 seconds will pass before vehicle begins to move forward after shifting into D from R.

When this occurs driver reports that the transmission acts as if it remains in Neutral for a moment or two before shifting into D, even after the shift lever has been moved from R to D with D highlighted in the PRND321 display.

Transmission fluid and filter change was performed at 99,000 miles. Fluid was found to be within normal limits (not excessively dirty or burned), and no metal flakes were found in the pan (transmission fluid pan magnet not "dirtier" than normal).

Driver has not reported having seen the Check Engine lamp illuminate, but PCM has not yet been checked for history codes with a scan tool.

Internet research regarding similar shift problems did not reveal anything (causes, fixes or other people that have encountered the same symptoms).

Any ideas? Thanks very much.

3,391 Posts
trans pressure solonoid perhaps?
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)

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
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