I have a 2003 monte Carlo ss with 136000 miles on it and every once in awhile the transmission will shift hard into all the gears and also sometimes it slips when you take off from a stop sign. But if you shut the car off and turn it back on it goes away. As far as I know the trans has never been serviced. Any suggestions??

 

First thing, change your tranny fluid and filter, don't do a flush as it will loosen the crud in your tranny and could cause more problems.

Secondly your shifter solenoids are sticking and the line pressure it takes to cause them to shift is increasing to a higher shift point which is causing the hard shift you are experiencing. They call this a long shift or P1811 code that the tranny will throw.

You tube videos




there are a lot more video's but those will get you started and give you a good idea of what is going wrong and what needs to be replaced.

When mine started doing this I changed the fluid and lived with it and I got over 100 000kms before the tranny finally gave out

Here's a couple links to the parts that need replacing. A tranny shop can do this but I am not certain on how much they will charge, but if you are handy with wrenches you can perform the "operation" yourself in your driveway, there are video's with step by step instructions on youtube that are invaluable

Pressure Control Solenoid

4t65e Pressure Control Solenoid


Shift Solenoid link is just below

Shift Solenoid