Does anyone have any information about locating the steering "evo" sensor on a 98 Z71? I would accept any helpful advice on this subject. I already changed "U & L " balljoints, tie-rods, and tires. Just to name a few ...... Any idea on how to find the part number ?

Welcome to AF.
What is it doing or not doing?
On the part no your dealer can run vin no and get the part and should have a picture of where it is located.
MT

Thank You for responding so quickly to my question. At times it acts like it has a mind of its own. Sometimes the steering goes basurk and will jerk or pull to one side. I can sometimes turn off the key and then restart it and it'll do just fine. I have done a little bit of research and all things lead back to this steering 'evo' sensor located somewhere on the steering column. If you have any input I'd be grateful. Thanks.:smokin:

The valve could be sticking or even bad wiring on system.
If electronic steering get it on a scanner and check for codes.
Post back code no. if it has any past present or history C codes.
MT

Lots of things involved in this system. EVO= Electronic Variable Orfice. Or variable effort steering. So heres a list of components.

1. EVO/Passlock module.
2. VSS(vehicle speed sensor)
3. HWSS(Steering Handwheel Speed Sensor) commonly referred to as the EVO Sensor.
4. Steering Assist Control Solenoid. Bottom rear of the pump.
5. And of course wiring.

Many folks here have fixed problems similar to yours by replacing the HWSS (EVO sensor), myself included. But before I did that I wanted to make sure it was an electrical (EVO) problem and not mechanical. I removed the electrical plug from the pump. Steering was easier at speed but no jerky surprises. Replaced the HWSS(EVO sensor) and all has been good.

Because there are so many components in the system you really should do as MT says and see if there are any DTC's starting with a "C" (C0472) is an example.

Anyway the HWSS (EVO sensor) is located on the lower column just before it goes thru the firewall. Need to disconnect the intermediate shaft from the upper shaft and slide it down towards the firewall. The sensor is on the lower bearing with wires going to it. Make sure you disconnect the NEG batt cable before attempting this as you're in the "air bag" danger zone..