99 K1500 Sub Steering Problem

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Bought a 99 K1500 Suburban with 135K miles. Had upper and lower ball joints, pitman arm, idler arm and IA bracket replaced when we bought it. Now has 155K miles.

It has recently developed a steering problem. First noticed it at lower speeds, 30 to 40 MPH when making lane changes. Turn the wheel to change lanes and the resistance feels normal. Then it feels like the resistance to steering input goes to zero - the steering feels real soft and it tries to oversteer. Then the steering feel comes back to normal.

The problem is intermittent but seems to be happening more. It recently happened at highway speed when changing lanes.

Had it checked out. Shop told me the ball joints, pitman and idlers arms were all OK. He guessed maybe it was the steering gear box.

There is no noise and no mechanical roughness in the steering.

Any advise on where to look for a cause of this will be appreciated.

Thanks

Jim
 
did the mechanic check if you have speed sensitive steering?
there would be a solenoid on the output side of the power steering pump, the faster you go the lower the pressure.
my thought is if the valve sticks open you would get too much assist at speed. If that is not the cause then you are back to a bad steering box.

EVO=Electronic Variable Orifice. Basic principle of operation: There is a solenoid on the outlet of the power steering pump that controls a valve. At idle or slow speeds, the valve is full open, allowing maximum fluid flow and, thus, maximum power assist. As speed increases, the computer monitors vehicle speed and another sensor that tells how fast the steering wheel is turning, and sends a signal to the solenoid to decrease the opening of the valve. So at higher speeds you get "less" assist.
 
I asked him if the vehicle had variable steering assist and could that be the problem. He said he believed it had what he described as a "valve" on the power steering pump. Sounds like the EVO you mentioned.

He made no attempt to troubleshoot the EVO or the gearbox.

If this is going to get down to removing and replacing components one at a time rather than actually diagnosing the problem, maybe the EVO is the place to start. I assume it costs less than a new steering gear box.

Many thanks zora.

Jim

p.s. I see there is also a "steering wheel position sensor" - I assume that is involved in EVO operation as well.
 
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I would think that component is intended for Stabiltrak, the vehicle senses you no longer have control of the vehicle based upon steering wheel position and the angular motion of the vehicle similar to a gyroscope. It then would use the abs system and throttle to regain control of the vehicle. Do you know if you have Stabiltrak?
 
Don't know about Stabiltrak. I did not get the original window sticker and have not tried to decipher the build "codes" on the glove box sticker.
 
I had a 1999 4X4 1500 suburban and drove the wheels off of it for over 250,000 mile before I sold it and bought a 2010 same setup. I had to replace the steering wheel sensor 3 time over the years I had it. Easy fix on steering Colum above brake pedal, you will have to separate the steering shaft under dash to get it done but very easy.

Your issue is exactly what mine did, felt normal then would jerk toward turn real easy, kinda scary.
 
jwd621 said:
Easy fix on steering Colum above brake pedal, you will have to separate the steering shaft under dash to get it done but very easy.

Your issue is exactly what mine did, felt normal then would jerk toward turn real easy, kinda scary.
Click to expand...

That sounds like what mine is doing - turn the wheel and then it feels like the power steering goes soft but turns itself farther than you want.

It is definitely spooky.

Just checked under the dash - there is a 3/8" thick gray plastic donut wrapped around the steering column above the brake pedal. That gadget looks like the pictures of a steering wheel position sensor on rockauto.

I'll give it a try....many thanks.
 
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