GS300 gear box trouble

[Robbob]

Hi can anyone advise. I live overseas and the machanic here are not the best, so need to check to see if anyone has any suggestion before I order parts.

My 2007 GS300 runs perfectly, until a couple weeks ago when I lost reverse gear. When the car stars first thing I have no reverse gear, however after running for about 20/30 mins the reverse gear works fine. So reverse when the engine is warm but no reverse when cold. The mechanics diagnostic check only showed there was a fault now resolved but does not state what the fault was.

does anyone have any suggestion as to what the fault might be and how to resolve it.

 

Many Thank my email is pp6000@hotmail.com 

feel free to drop me a message or reply here.

[johnatg]

I think I'd try changing the gearbox oil - the whole lot, which I think will mean doing several drain and refills using the drain plug, or remove the sump to get it all out in one go.

[ColinBarber]

Certainly check the level and colour/smell of the existing fluid, but I would just replace it by doing multiple drain/refills.

18 minutes ago, johnatg said:

or remove the sump to get it all out in one go.

even that won't get it all out as there will be 1/2 the capacity still in the valve body and torque converter. 

[Robbob]

Hi guys thanks for the suggestions.

someone has said there is a chance there in a blockage in the internal tubes. Where pressure builds these tubes allow the fluid to move and this is what pushes the switch that puts the car in reverse. 
 

when the car is cold the blockage stops the fluid moving, when the gear box gets ward the blockage dissolves a little. This is why the reverse works when the car has run and got warm. For me the logic seems to make sense. However the advice came from someone not familiar with Lexus cars so wasn’t sure about the best way to remove the blockage.

Does anyone have any thoughts on this diagnosis and if it is correct, any thoughts about the best way to remove the blockage?

 

many thanks for  reading this message 

 

[ColinBarber]

If the fluid is good then I would suspect the reverse solenoid sticking rather than a blockage in the valve body which would be highly unlikely without poor fluid and other issues.

[steve2006]

Hello Robert and welcome to the LOC, could you provide a few more details regarding the car?
Current mileage and service history?

Has the transmission fluid ever been changed (drain and refill) ?

Is the fluid level correct?

The fault code would help, could you ask the mechanic what it was?
 

Given that the transmission fluid temperature is critical for obtaining the correct level and the transmission already has a fault I would begin by draining and refilling a few times with the correct fluid (Toyota WS) used in the Aisin A760E six speed transmissions. There is a specific procedure involved for doing this which I can email if required.

 

[Robbob]

Hi thanks for all your thoughts 

the car is a 2009 GS300 with 70,000 miles on the clock, I have full service history and apart from this issue the car runs really well.

i am not sure it the gear box has ever been drained so that’s maybe the first step to try.

any info you can send would very much be appreciated.

I am overseas so I don’t have the luxury of a Lexus dealer. I have a very good local machanic who before starting working for himself was a machanic for a US Mercedes dealership and I trust him. When he attached his diagnostic kit it only showed that the car had a malfunction with reverse and that is now normal. It doesn’t give any code to say what the malfunction was. 
 

Thanks in anticipation for your reply. 

 

pp6000@hotmail.com is my email address.