Code p1811 what does the trans do or not do with code problem p1811 I cant find any info on this ?

try review this video.
4t65e P1811 Common Problems and How to Fix Them Transgo 4t65e

the side pan will have to be removed and axle shaft plus lower left side of the subframe for clearance and then remove the valve body assy ..there are several ball bearings positioned in strategic locations for pressure control that is not put back in the right position this trans will not shift correctly also when bolting the valve body back special torque sequence must be performed or the trans will still have a harsh shift . I recommend that a qualified transmission shop do the work on this trans or you are throwing away your money ...sorry

P1811....Long shift and maximum adaptation limit reached
It means that PCM have found long shift and the adaptation pressure is at maximum
Seal cut, clutch worn out. and so on overhaul trans.
check oil level first
hope it help

p1811 is a transmission code for trans adapt long shift. There is a service bulletin for this code that recommends replacement of the pressure control solenoid in the transmission.

This is common on your car. You have a HydroMatic 4T65E trans. You will need the Pressure Control Soleniod Valve Assembly change in your trans. It is tetious work so you may need to take it to the shop for repairs.

If all gears are shifting hard, may have a code p1811 set-trans adapt long shift. When this code sets it commands full line pressure causing hard shifts. Usually the pressure control solenoid is at fault. You need to have it scanned for codes.

p1811 dosent exist

P0420 catalytic below threshold,Your basically dealing with is a failed catalytic ,
P0742 Torque convertor clutch circuit stuck on or off.
P1811 this is manufacutrer code definition adaptive shift (due to P0742)
P1811 this code is set from towing a trailer in overdrive
when P0742 comes on it usually is accompanied by P1887
If its p1811 then yes it truly is a TCC solenoid being a problem As for catalytic code te catalytic is a mechanical device and yes they do expire from mileage and age

their are several different solenoids in the trans, all located behind the drivers side cover, the most likely cause of a hard shift is a code p1811 caused by a faulty pressure control solenoid. this is a common problem and their are updated solenoids available to solve this problem