2006 Lucerne v8 TCM transmission

[angie2short]

I have a 2006 lucerne with north star engine. I have replaced the TCM. The tcm says the transmission is in 3rd gear then put into drive. You can kinda manually shift the car. But 3rd is the highest it will go. Any helpful hints.

 

[2007LucerneCXL]

Get the transmission professionally scanned for codes.

 

[angie2short]

Get the transmission professionally scanned for codes.

Have done that. We think we are chasing a wire by the tcm. I know that this is a common issue with the 2006 lucerne. Only good for 155,000 miles.

 

[2007LucerneCXL]

Check the Cadillac DTS forum as they have more experience on the 4T80E transmission.

 

[Lucerne CXL 11]

You know that the TCU is coded to the vin of the car it was in right? If you take a ECU or a TCU or most electrical parts from one GM car to another that you have to re-vin them. It's a anti-theft measure GM has been doing for 20+ years and it's a pain.

You need to Re-Vin, Re-Learn adaptations and sync it with the ECU and Canbus system. Also Update firmware so you get the best performance from it. You can no longer just plug and play.

 

[angie2short]

You know that the TCU is coded to the vin of the car it was in right? If you take a ECU or a TCU or most electrical parts from one GM car to another that you have to re-vin them. It's a anti-theft measure GM has been doing for 20+ years and it's a pain.

You need to Re-Vin, Re-Learn adaptations and sync it with the ECU and Canbus system. Also Update firmware so you get the best performance from it. You can no longer just plug and play.

Yes i have already done that.

 

[Lucerne CXL 11]

Try replacing the Input Speed Sensor (ISS), checking that the shift cable is aligned otherwise it might be the valve body in the transmission. With 155k if you have not changed the fluid every 60-70k miles you can get build up causing shift issues. I would change the fluid and filter and run a good transmission additive like Lubegard 63016 Platinum Universal ATF Protectant, 15 oz. If there is not enough pressure or there is a blockage you wont be able to shift into gear. Also if your not getting into 4th gear you torque converter is not locking up causing the transmission to overheat making more issues.
Changing fluid WILL NOT damage your transmission. The damage was already there if you have any issues after a fluid change.