Hey i have a question concerning my trans. The shifts from 1-2 are very hard and i have never felt this before. As i noticed this I was curious is it was the trans or just vibration because the car was lowered. So i was going 20 miles an hour and i down shifted into 2nd because thats were the harsh shifting was from. And sure enough the car banged into second and you could feel the car vibrate. After some research i think it could be this but I am not sure because I am no expert at all on these transmission i could use your guys help. The pump is always whining a lot and the shifts seem to take longer like i am giving it more gas therefore making more pressure in the trans lines.
Intermittant Harsh Shifting / Pump whining, Possible Code P1811:
This is perhaps one of the most common problems with this transmission. It has been a problem since the release in 1997 and can happen for no reason at all even with clean fluid and very low mileage. The EPC solenoid is probably bad and again is very common to happen. The EPC solenoid controls line pressure and has a spool valve which oscillates back and forth to regulate transmission line pressure based on commanded pcm signals dependant on lots of various inputs of the vehicle. The spool valve in the solenoid will bind up and cause loss of pressure control from the pcm. The pcm constantly monitors shift timing in milliseconds and if this is not within programmed parameters after a few shift cycles the pcm triggers trouble code P1811 which is Max Adapt / Long Shift. This code will not set the SES light but will dissable all adaptive shifts and will max out line pressure in the transmission which causes the harsh shifts and can also cause the transmission pump to whine because it is supplying fluid at a high rate and pressure and puts more stress on it thus creating the whine. Generally shutting off the car will make this condition go away until you drive a few more miles or the vehicle warms up and the harsh shifting will return. Replacing the EPC solenoid will most likely correct this condition and again is probably the most common problem found in any year of this trans. I will also add that a worn out transmission can cause this. If the fluid looks bad, dark, and smells burnt or lots of fine dark sludgde or a dark film of material is in the bottom of the pan then there is probably internal damage. Once clutches become burnt and have excessive wear shift timing will be greatly extended and the pcm will fall outside of its set parameters and code P1811 will turn on, again commanding higher line pressure and harsh shifts but an overhaul in this instance is the only proper fix.
Intermittant Harsh Shifting / Pump whining, Possible Code P1811:
This is perhaps one of the most common problems with this transmission. It has been a problem since the release in 1997 and can happen for no reason at all even with clean fluid and very low mileage. The EPC solenoid is probably bad and again is very common to happen. The EPC solenoid controls line pressure and has a spool valve which oscillates back and forth to regulate transmission line pressure based on commanded pcm signals dependant on lots of various inputs of the vehicle. The spool valve in the solenoid will bind up and cause loss of pressure control from the pcm. The pcm constantly monitors shift timing in milliseconds and if this is not within programmed parameters after a few shift cycles the pcm triggers trouble code P1811 which is Max Adapt / Long Shift. This code will not set the SES light but will dissable all adaptive shifts and will max out line pressure in the transmission which causes the harsh shifts and can also cause the transmission pump to whine because it is supplying fluid at a high rate and pressure and puts more stress on it thus creating the whine. Generally shutting off the car will make this condition go away until you drive a few more miles or the vehicle warms up and the harsh shifting will return. Replacing the EPC solenoid will most likely correct this condition and again is probably the most common problem found in any year of this trans. I will also add that a worn out transmission can cause this. If the fluid looks bad, dark, and smells burnt or lots of fine dark sludgde or a dark film of material is in the bottom of the pan then there is probably internal damage. Once clutches become burnt and have excessive wear shift timing will be greatly extended and the pcm will fall outside of its set parameters and code P1811 will turn on, again commanding higher line pressure and harsh shifts but an overhaul in this instance is the only proper fix.
