The hot topic always seems to be transmission complaints for the GS300. I found some info as well as a possible solution to transmission problems with the GS300. Enjoy!
The fist info applies to the 93-99 GS300
A340E / A341E / A343E / A350E
The transmissions above are rear wheel drive 4 & 5 speed automatic transmissions. The A350E is the 5 speed. They are computer and throttle pressure controlled. Common symptoms are transmission shifting erratic, slipping or not shifting at all. Also the check engine light can come on.
External sensors like the throttle position sensor, vehicle speed sensor or output speed sensor quite often go bad, causing these symptoms. Always run a scanner first to see if a sensor is causing your problem. Also check the throttle pressure cable that goes from your transmission to your carburetor or throttle body depending on the configuration of your engine.
On most of these models, they have a diagnostic box you can retrieve codes with. The location of this box should be in your owners manual.
If all checks out well then this may be your final solution!
transmission chip!
:D