well i have a 03 monte carlo ss my original tranny had 160000 miles on it and it threw a p1811 code so i was told tranny was shot so i got a used tranny that had 90000 on it and now that one threw the same code and also when i stop and go at a light it dosent go till about 2000 rpm then it clunks and goes. can anyone help me. P.S im getting one now that has 60000 on should i do anything to that one so it wont do the same thing.

 

Try getting a high-flow catalytic instead of dumping all your money on transmissions.

 

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.

i have this very same error on my trans, i have purchased a used trans with 15k on it...but that's not saying this will not come back... the only TRUE way to solve this issue is a rebuild (they can then replace the EPC solenoid with an upgraded model).

i hope this help you to understand whats going on!

 

Well Thats Messed. becase i blive thats the code that was thrown on my car. Why Do people say its the Cat then?? Like month ago engine light comes on not sure of code but ment ( c02,exhust leak,cat, ) then 2 weeks after that code my car had a long/hard shift then throw 1811 code.. Soo im really confused. and this is a 05 SS 64000kms