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Discussion Starter #1
I'm new to automatic transmissions. I've driven manuals my entire life, but the wife was tired of shifting so we got the IS.

What is the difference between the stock trans and an upgraded trans like the Level 10? Does a new trans means it gets all new mechanical internals? New bell-housing?

What is the performance difference? What do you gain? What are the beneifts for the street, if any?

Does the car have to be in a garage for a long period of time?

Are these even valid questions?
 

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The main upgrade they would do is to raise the stall speed of the torque converter.

What it would mean is basically when you step on the gas the engine revs higher (and more into the "power band") before power starts to go to the rear wheels.

Low speed performance (particularly from a stop) would improve, but you might get "jumpy" shifts and reduced gas mileage.

Another upgrade they can do is to increase the fluid pressure inside the unit. This wouldn't make much difference to an otherwise unmodified IS300, but becomes important if your engine is modified to make more power.

Thats about all I know. Someone else who knows more details should post in here too.
 

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Discussion Starter #3
Thanks TEG,

But I still don't get it. As I understand it, only the torque convertor is changed/modified.

Are the individual gears modified? Do the ratios get closer?

How does a higher stall rated torque convertor translate into real world power at the wheels? Is this trans mod needed only if you have radical engine mods such as NOS, superchargers or turbos?

Is it worth doing for a stock motor that may get an intake in the future?
 
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