The P0811 indicated there is excessive clutch slippage. The PCM (Power Control Module) controls transmission shifts. The PCM also times how long each shift takes. If the PCM notes that the shift times are too long, the code p1811 will be set. A faulty transmission fluid pressure control solenoid can cause this problem. The solenoid needs tested as per GM procedures. If it fails, then it should be replaced. Chances are this is what is causing your problems.
The P0741 indicates a torque converter clutch circuit stuck on. This code can be caused by low fluid, very dirty fluid, the clutch solenoid valve, wiring, or there could be an internal issue. What I have found over the years is that most times, the problem isn't related to the electrical components but rather dirt which restricts flow of fluid to the solenoid. It wouldn't hurt to flush the transmission. Also, it would be a good idea to remove the pan to check for excessive clutch or foreign material materials which could indicate worn clutches or hard part damage. If that is found, then the transmission will either need rebuilt or replaced.
Does the transmission need replaced? Chances are NO. However, you should have a shop inspect it that you trust and will do the proper tests to determine where the problem is coming from. Also, 80K miles shouldn't have worn the transmission out unless it was abused.
Wednesday, May 20th, 2015 AT 8:49 AM