Wiggle when BRAKING

[Roger08LTZ]

I was originally thinking of just replacing nearly everything in the front end as my Tahoe has 195,000 miles on it, but the components are adding up to more than I'm willing to spend right now. I have a Z55 suspension and all parts appear to be original or GM replacements. I'd like to identify the true cause of the issue rather than rebuild the entire suspension.

The symptom: When at highway speeds I hop on the brakes, there is a wiggle, where it pulls a bit first left, then right. The usual suspect for a pull when breaking is of course the brakes, but after this first wiggle when the car comes from full highway float to nose down then the breaking is dead straight no matter how hard you press the brakes, you can have your hands off the wheel and it stops dead straight. It's just the moment when the nose drops when the car seems to be unstable, so I'm thinking suspension. Next week, I'll run this up on the lift and check it out. Just wondering if there are some usual suspects to look for. I'm not sure when this started as this is my wife's car and I don't normally drive it. This week I'm driving it, it's not that bad, but it doesn't feel right and I'd like to correct it.

The rear air shock air bags are completely torn and the compressor does not work, but it sits just fine without the air shocks working. We almost never load much cargo or tow with this car, so I think I'm going to ignore the rear for now and focus on the front as I feel this wiggle would be from the front suspension.

Any ideas what would cause this wiggle when breaking at highway speeds. Thanks!

 

[B-train]

I'd look at upper control arms for sure - at 195k, the upper ball joints are most likely shot. Probably due for lower ball joints and then maybe tire rod ends if needed.

The way you describe it make me believe the same as what you suspect. Once the suspension/alignment squares itself back up, them it brakes straight and doesn't move. Just spend the money on new OEM parts and redo anything needed up front. As for the rear, if the compressor is still working just do Arnott shocks to save some money. Otherwise OE aren't too awful and just keep it like it was.

 

[Joseph Garcia]

As @B-train suggested, I'd first look at control arm bushings and ball joints. If there is any play, replace both the upper and lower control arms with OEM parts, which will include the ball joints.

I'm assuming that you have struts on the front, and if you do, one completely collapsed strut with no damping at all could be a cause of the nose dive.

 

[mb1500]

Tire condition / PSI? Last alignment was?

 

[Geotrash]

Sway bar end links.