A customer of mine that I have been helping over the past few months on the phone to get his buick fixed, lost 4th gear, called me today saying he was having problems getting it to start. He mentioned having to move the shifter around and the lights on the dash indicating what gear position you were in were randomly lighting up but not in the correct spot. This was causing the car not to start. Right off the bat I knew what had happened as I have an update tech manual describing this exact problem and having a 4T65E apart with the internal type PRNDL switch I can see how easy it would be to do this. Below is a pic of the correct and incorrect way to install the detent spring on the over the internal mode switch. The bulletin states that this will generally NOT store a code in the pcm and that this problem will exist after repair from removing the channel plate inside the trans. Some 99 and up cars with the 4T65E transmission had this switch, Grand Prix through 03 did NOT, they still used the external switch but most other carlines started to use the new internal switch. I just wanted to share this for those brave enough to dig into your own transmissions whatever the reason, gear ratio changes included!
Originally Posted by Trannyman95
