My 05 LS430's 6 speed transmission has been shifting pretty rough occasionally. When it happens its at low speeds it feels like youre in the car with someone driving a manual who isnt that great at shifting. Along with that whenever I put it in drive. about 1-2 seconds after it feels like thats when it actually shifts into 1st and the whole car feels like it wants to jump forward for a second. everyone feels it including passengers. I always come to a full stop before shifting and wait to let off the brake until it does the weird forward movement. Was wondering if anyone knows what either of these problems are/are from and how to fix either of them. Thank you for any help!

 

Sounds like your ECU needs some work. Common issue with the 04-06s.Here's a vendor that fixes it
https://taninautoelectronix.com/prod...ough-shifting/

 

I dont know much about this car, where could I find the VIN they describe to look for, both the 16 digit one and the ten digit one. (example of the 10 digit one : 89661-50692 )

 

The VIN should be in your door frame or the bottom left of your windshield.
The ECU is in the engine:

 

thank you very much this is a lot of help. deeply appreciated

 

Do you think its fine to unplug the ecu while the battery is connected or is it best to disconnect it?

 

Disconnecting the battery would always be the safest way.

 

Yes, always unplug the negative when dealing with electronics.

 

Vin for car bottom of windshield on dash driver side. Absolutely disconnect power for ecm removal.

 

 

One other tip - when you get it back from repair, be certain you hook all the connectors up to the proper receptacles - DO NOT MIX THEM UP. That happened to a LS400 owner a year or two ago and that simple mistake gave him no end of grief until he finally figured it out, car wouln't start, all kinds of issues. There is a thread on that in the LS400 forum, I could see this possibly happening with the LS430 ECU.

 

Sir it shifts down rough but not up rough, it’s the ECU. Had the issue on my 2005 LS. Sent ECU to a shop in TX, which repaired it. So far, 2 yrs later, no issues.