Hard Turn Left

[BlakeJb]

Hey guys. 
just the other month my ‘15  Sierra started making real hard turns to the left without me turning the wheel. Here’s the details...

 

I get on the highway and get over 60mph. I’m in drive, not some up or down gear. Then about once a week the truck turns by itself to the left, real hard.

 

just to be prepared for it happening I keep my hands tight on the wheel at all times. You can imagine how this is troublesome.

 

The warranty is out so GMC won’t touch it. The shops can’t diagnosis. I also haven’t found anything on the forums. You guys have any ideas whats going one?

[davester]

Did they go over all the front steering and suspension parts, including the mounting points on the frame?

 

You might consider mounting something like a go-pro in the wheel well pointing down, and then reviewing the video when it happens.

 

It wouldn't surprise me if a joint in the steering has failed in such a way that under more pressure, it pops out, but then returns to the "correct" position at lower pressure and at rest.  Or a mounting point failing in a similar way (for an a-arm, or perhaps the idler arm).

[BlakeJb]

That is a really interesting idea. I’ve have not heard someone suggest that yet. 
 

the guys at the dealership and shops are mainly focused on electrical components failing in some way. 

[davester]

What gets the truck going straight in a "normal" way again?  Just slowing down a bit, or do you have to stop the truck or power cycle it or something else?

[BlakeJb]

What gets the truck back under control is I let off the gas, I slow down, and it slowly comes back to normal. 
 

what should be known though is that this steering problem doesn’t happen all the time. I can be every few days it might happen. 
 

I do know that it takes going over 60mph to make it happen. I also do not need to turn for it to occur. All I need to do is drive straight and over 60mph.