So I was asked recently what is the deal with an EVO on a Lexus Steering Rack. Do I need that? Can I buy one with out? What is Servotronic?

First off, what is a servotronic unit? A servotronic unit, often referred to as a EVO or variable assist steering module is a computer assisted steering rack. The rack is not electric, it is still powered by hydraulic pressure coming from the steering pump, but the amount of pressure or assist coming from that pump changes depending on the speed of the vehicle. Drive faster and you need less assist. Make a turn in a parking lot and you need lots of assist.

If a vehicle came from the factory with EVO or Servotronic such as the Lexus LS400 steering rack , then you need to put back on a steering rack with the EVO on it. Most late model high end vehicles, such as most Mercedes Steering Rack have these units built in. Since the EVO is tied to the computer of the vehicle, you cannot really add an variable assist setup on the rack.

One more thing to keep in mind. The servotronic unit can be removed from the rack, see below. So often you can buy a rack ’supplied without evo’ and you can swap yours over. Since the EVO’s are expensive, this could save you lots of money if you just have a leaking steering rack or something else not realted to the EVO.