99 Suburban Steering Box

[KellyM]

I have a '99 Suburban 3/4 ton 4X4 with a 7.4L that is going to need a new steeering box. The local dealer (Boise) tells me they can't get them any more. Does anyone have a source? The rig is completely stock with 56,000 on the clock (I bought it new), but it has been adjusted to the point where therr is no more room for adjustment. I also would like to tighten up the suspension, so any recommendations for that would be great too. I intend it keep it stock, it is used more for towing, people hauling and mild logging roads.

Thanks,

Kelly

 

[Larry]

If you are looking for a “brand new” steering gear box, they’ve probably been discontinued for years but you can find remanufactured gear boxes all day long from just about any parts store from Autozone to Napa and so on. 56,000 is nothing as far as mileage. Has anybody bothered to verify the EVO (electronic variable orifice) steering isn’t the actual culprit? This wouldn’t be the first time I’ve heard of people adjusting the steering gear to death when the problem is actually a failed $50 handwheel speed sensor at the base of the steering column.

Here is the EVO steering description from the service manual:

The electronic variable orifice (EVO) system increases or decreases the amount of fluid leaving the power steering pump. This provides the driver with a comfortable balance of steering wheel feel and power assist.

At vehicle standstill or at very low speeds, the system allows full hydraulic fluid flow for maximum power assist and reduced steering effort. As the vehicle gains speed, a variable orifice closes at the steering pump which reduces the pump fluid flow. This action provides a stiffer steering wheel response for an improved road feel and a greater directional stability at highway speeds.

A sensor mounted on the steering column detects the steering wheel movements associated with defensive driving maneuvers. A control module uses this sensor input and the vehicle speed in order to adjust the amount of current to the solenoid.

The EVO system consists of the following components:

•The power steering (PS) solenoid actuator is located on the power steering pump discharged fitting.
•The EVO/Passlock™ module is mounted on the instrument panel carrier, beneath the radio.
•The steering handwheel speed sensor (HWSS) is located in the lower bearing of the steering column.
•The vehicle speed sensor is located on the transmission output shaft or on selectable four wheel drive the transfer case output shaft.
•The powertrain control module (PCM) is located in the engine compartment on the left inner wheel well panel (diesel engines only).
•The vehicle control module (VCM) is located in the engine compartment on the left inner wheel well panel (gasoline engines only).

 

[KellyM]

Thanks, Larry. That was my thought originally as well. I specifically asked about the EVO, and the shop said it was fine. Is there a test that I can do to see if the EVO is bad? I guess at $50, I should just replace it. I have the common wandering steering feeling, and since my daughters drive the truck I want to tighten up as best I can. I replaced the idler and pitman arms and the bushings at about 30,000, but that was probably 6-7 years ago. I asked about that gear as well and the shop said it was fine, and suggested it was the uneven road surface. Maybe time for a new shop.