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Posted

Hello folks, I have a 2002 LS430 and gear box has got me baffled.

Original symptoms:
Last time I took her a long drive after 3 miles it felt like she was stuck in 1st gear and crawled home on high RPMs



What have I tried:

I have drained the gear pan oil not once but twice.
Carried out all the things you do when changing gear oil (Toyota type 4), cycled though the gears.
Gear oil at correct level.

Installed a new battery with more than adequate power.
ECU reset with the gas hold in key on and remove after 2 minutes.


Symptoms after what I have tried:

I can put her in reverse and I feel the bite and she reverses on my driveway when brake released.
Then put her into D and feel the bite and she moves forward on my driveway when brake released.
I will do this a couple of times and then she stops biting, the RMPs adjust at gear change but no physical bite or movement.
When I put into P and restart the car the same as above works again for a few minutes.
Connected cheap OBD reader and no error codes.

I have noticed that when she starts up she sounds tinny until put into gear.

 

Any help on this to troubleshoot any other areas would be great full as I want to keep her on the road.


Posted
6 hours ago, clyle2000 said:

Hello folks, I have a 2002 LS430 and gear box has got me baffled.

Original symptoms:
Last time I took her a long drive after 3 miles it felt like she was stuck in 1st gear and crawled home on high RPMs



What have I tried:

I have drained the gear pan oil not once but twice.
Carried out all the things you do when changing gear oil (Toyota type 4), cycled though the gears.
Gear oil at correct level.

Installed a new battery with more than adequate power.
ECU reset with the gas hold in key on and remove after 2 minutes.


Symptoms after what I have tried:

I can put her in reverse and I feel the bite and she reverses on my driveway when brake released.
Then put her into D and feel the bite and she moves forward on my driveway when brake released.
I will do this a couple of times and then she stops biting, the RMPs adjust at gear change but no physical bite or movement.
When I put into P and restart the car the same as above works again for a few minutes.
Connected cheap OBD reader and no error codes.

I have noticed that when she starts up she sounds tinny until put into gear.

 

Any help on this to troubleshoot any other areas would be great full as I want to keep her on the road.

Quote

It sounds like you've already done a thorough job troubleshooting your 2002 Lexus LS430's transmission issues. Based on similar cases, here are a few possible causes and next steps:

Potential Causes

  1. Failing Shift Solenoids – These control gear changes and can cause erratic shifting if malfunctioning.

  2. Transmission Fluid Pressure Issues – A sticking pressure regulator valve or worn transmission oil pump could lead to shifting problems.

  3. ECU or Transmission Control Module (TCM) Issues – Some LS430 owners have reported that ECU faults can cause shifting problems, even if no error codes appear.

  4. Battery Voltage & Electrical Connections – Even with a new battery, weak electrical connections or a failing alternator can affect transmission behavior.

  5. Torque Converter or Internal Transmission Wear – If the transmission engages briefly but then loses bite, it could indicate torque converter failure or internal clutch wear.

Next Steps

  • Check Transmission Solenoids – A mechanic can test and replace faulty solenoids.

  • Inspect Wiring & Grounds – Ensure all transmission-related electrical connections are secure.

  • Consider an ECU Inspection – Some LS430 owners have resolved shifting issues by repairing or replacing the ECU.

  • Perform a Deeper Transmission Diagnostic – A professional scan tool (beyond a basic OBD reader) may reveal hidden faults.

 

 

 

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