Burb shakes when braking - INTERMITTENT

[fozzi58]

TL;DR I have an intermittent shake (front to back) when I hit the brakes. Feels like a bent rotor but its not the brakes.


Full Story

Back in September I did a bunch of work to the truck - supercharger, torque converter, new driveshaft, Wilwood BBK up front, all the supporting mods etc. For a couple of months the truck just ran with no issues, like it was supposed to. Around November I started getting a front to back shake when I hit the brakes. It feels like a certain part or the brake pad is grabbing the rotor harder than the rest as it rotates. Didn't happen all the time but you could feel it. I thought at the time it was the back brakes. The pads were really low (62k on the truck) and there was some scoring on the rotors. Figured it was a simple fix.

Swapped out the OEM parts with Stop Tech rotors and new pads. Same issue. Kinda odd. Drove on them for about a month and then took it to the mechanic that's been handling all the mods on my truck. He wanted me to get replacement calipers and start over with everything new to make sure, and he also suggested I get steel lines for the rear as well. He let me order whatever I wanted. I went with the PowerStop rear kit which included calipers rotors pads and I ordered the steel brake line kit also just for the rear lines since the Wilwoods came with braided lines.

All that work was done and she is still doing the shake. The connecting ties on the front sway bar were also replaced with poly cause they were looking worn. Lastly, replaced the rear tires with a brand new set (05/13/22) cause the ones out back looked to be dry rotting. Front tires were done 6 months ago so all 4 tires have less than 7000 miles on them.

Its still shaking. *sigh* Again its intermittent. I can cruise the highway at 80mph, smooth as glass and as soon as I touch the brake pedal the shaking hits in. The harder I press the more violent it gets. Other times I can be diving into a corner on an off ramp, jump on the pedal and she slows down without any feedback in the truck. It comes and goes on the same drive and its driving me insane cause I am not seeing any issues otherwise. Obviously there is something going on but neither me nor my mechanic want to keep throwing money at parts that aren't going to solve the issue.

Mechanic checked the new PowerStop calipers to make sure they weren't seized, he mic'd the rotors and make sure they where perfectly flat. There's no slack in the drive train; the new driveshaft was done by a very reputable speed shop who my mechanic has used for a long time with never an issue. The wheels are true; high speed balance on the tires; no bends in the wheels; hubs checked to make sure they were true also. I also bought a heat gun, did some very spirited braking, and took the temps of the rotors. Did this a few times. I'm averaging 120 degrees up front and about 90 degrees out back. So the brakes are doing their jobs and dissipating the heat as expected. The calipers are clocking in at lower temps than the rotors which is to be expected so I have to believe the brakes are NOT the cause of the issue.

This shaking isn't coming through the brake pedal or through the steering wheel like ABS feedback or a bad front rotor - you feel it in the seat and the truck reverberates throughout - dash, steering wheel, and the passengers feel it too. We are both leaning towards a possible suspension issue. However there are so many other possibilities. Speed sensors on the wheels? ABS? Suspension? Could I need an adjustable proportioning valve? Wheel bearing? Possible issue in the carrier? We keep thinking suspension because maybe the "intermittent-ness" depends on the load of the truck on the suspension. I tried testing this theory by making shaper turns while braking, trying to shift the load of the truck by hitting pot holes (I know...), jerking the wheel and then braking etc. Again, its no rhyme or reason, right hand turn at high speed - sometimes the shake, and other times not. Then again, this is seat of the pants and its hard to replicate turns and braking pedal pressure.

I don't want to throw good money after bad but I need this resolved and I'm at wits end on this one. I know we just had a thread from a Yukon owner with a similar issue, but everything that was throwing his truck off, I've already replaced with new parts, plus a full brake fluid flush. Any suggestion from someone smarter than me would certainly be appreciated. Thanks everyone.

 

[exp500]

Check both driveshafts.

 

[fozzi58]

Check both driveshafts.

Its RWD

 

[swathdiver]

I suspect that one of the pistons in the Wilwood calipers might be hanging up, intermittently. Since there are many and they are smaller, it may not cause a pull.

 

[exp500]

Remember, pinion angle changes under braking.

 

[skidaddytn]

>However there are so many other possibilities. Speed sensors on the wheels? ABS? Suspension? Could I need an adjustable proportioning valve? Wheel bearing?

Definitely check everything easy first. Wheel bearings are easy to check by jacking up each corner and checking for any side-side up-down play in the wheel. Usually you can hear a bad wheel bearing when turning, but I've had one go bad that was near silent. It caused steering wheel shake at higher speeds.

 

[CMoore711]

@fozzi58 I currently have a similar symptom I'm experiencing with my '15 Yukon XL Denali 6.2/8-speed. I too have Wilwood BBK on all 4 corners and it is not the brakes.

quick notes:
- Currently at 131K miles
- OEM Upper & Lower Control Arms w/ New Ball Joints replaced at about 115K
- OEM MRC shocks & struts at about 90K - currently no leaks
- Inner & Outer Tie Rods replaced at 115K
- Hotchkis front & rear swaybars and new endlinks at 110K
- Wilwood Front TX6R kit is <30K miles

Everything is tightened up and torque's as it should be. We've checked the front brakes more than once and the calipers are working as they should and rotors are in great shape.

My shake doesn't resonate from the front and to the back though; Mine seems to just be isolated to the front end area. But like you it's intermittent, driving me nuts that it's not consistent and easy to duplicate = hard to diagnose and figure out the true cause.

I have heard that GM did some updates to some of the front-end steering parts in 2017+ K2XX SUVs. Specifically with some revised steering gear bushings and potentially a revised Steering Gear Assembly.
Steering Gear Assembly GM# 84774227
Steering Gear Bushings GM# 84234960
The new Steering Gear Assembly does come with the updated bushings (2).

The Steering Gear Assembly is a rather expensive part and it is worth noting to my understanding must be programmed and setup to the vehicle by a dealer and I am not sure if the vehicle is drivable without being programmed. i.e. I am not sure if this could be removed/replaced yourself and then driven to a dealership to have them program and set-up after installed?

Another common source of "steering play" is the tilt coupler in the steering shaft in the steering column. You can hold the bottom still with a screwdriver and wiggle the steering wheel back and forth to see if there’s any play there. If this coupler is worn it would require replacement of the steering column. It is the steering shaft inside the steering column and the play happens where the column tilts.

I currently do not have any play in my steering wheel though and I'm not positive on what exactly to check specifically in the Steering Gear Assembly.

Unfortunately I don't have much additional insight or direction to add at this time. I just figured I'd post up my current experience/symptoms since they appear to be similar to what you've got going on and we have similar brake and suspension mods.

Subscribed for additional input and potential solutions.

 

[fozzi58]

@CMoore711
Thanks for the insight. I will def have all the steering components checked. Never thought about that. My mechanic is leaning toward suspension as a possibility. While I have the Hotchkis bars and new end links, I haven't done any of the other bushing replacements and I know I'm overdue for shocks/struts as well (coming up on 80k).

I did some more high speed testing on Monday (05/16/22) and when I let go of the steering wheel and jam on the brakes from about 85mph, the steering wheels moves back and forth just a little in sync with the front to back vibes. It also tends to pull to the right slightly. It was fairly consistent when I applied pressure to the pedal.

If I jam the brake and let off a couple of times, I can apply firm pressure and the shake goes away. Not consistently but its somewhat controllable. I also picked up a couple of cap stones for a wall I am putting together. They were about 125lbs each, had 2 of them - both in the very rear of the truck. The brake shake was consistent the whole time with that weight towards the rear most of the truck. I've driven with the wife and kids and the shake comes and goes. With all the extra weight in the very back of the truck, it was 100% consistent.

I'd be curious if you threw a couple of sandbags or weights in the very back would you have the same (or have had the same) consistency as I have?

If nothing else I feel your pain. This is infuriating. If I make any progress I will post and hopefully it will help you out. Conversely, I would appreciate the same reciprocation. Thanks.

 

[fozzi58]

Remember, pinion angle changes under braking.

I'm aware of that, but that would also mean I should have had this shaking since the day the new driveshaft was installed. That coincides with the Whipple, torque converter, brakes etc and when it was first complete, there were no issues for about 2 months of daily driving. That first 2 months included a round trip to Virginia (1000 miles) and multiple trips to our vacation home which about 150 miles round trip, plus local driving.

I suspect that one of the pistons in the Wilwood calipers might be hanging up, intermittently. Since there are many and they are smaller, it may not cause a pull.

We haven't pulled the front calipers off to check this. When I saw your post, I reached out to Wilwood tech support to see if they had a way to diagnose this without completely disassembling the caliper. Unfortunately my request has gone unanswered. Definitely something we will look into cause I cant leave any stones unturned.

 

[exp500]

Won't take long to remove driveshaft and feel for binding in U joints. Just Sayin. Leave no stone unturned and start with symtoms . Happens with braking. Brakes mostly eliminatated unless stuck caliper and you havent shot them for heat immediately after occurance. If it were suspension, rough road would be hard to drive.

 

[lyncht1967]

Change the tie rods. that's what it is. just did mine after nearly going INSANE. dont fool yourself into thinking they feel tight,... they may, but they aint. Do both and then begin to de-accelerate like youre on a cloud. Like I do now.

 

[CMoore711]

This symptom is driving me nuts! I'm getting frustrated not being able to pin point the cause of the problem.

Everything in my front end is tight.
Ball Joints
Tie Rods
Control Arms

The "brake shake" or pulsing sensation is NOT all the time. Sometimes it's present and sometimes it brakes very smooth as it should.

My front CV Boots are leaking a little grease; I'm not sure if the CV Joint is actually bad or failing, but the boots are leaking a tad. Could failing CV joints be causing this issue? If so why is it not happening all the time?

 

[fozzi58]

This symptom is driving me nuts! I'm getting frustrated not being able to pin point the cause of the problem.

Everything in my front end is tight.
Ball Joints
Tie Rods
Control Arms

The "brake shake" or pulsing sensation is NOT all the time. Sometimes it's present and sometimes it brakes very smooth as it should.

My front CV Boots are leaking a little grease; I'm not sure if the CV Joint is actually bad or failing, but the boots are leaking a tad. Could failing CV joints be causing this issue? If so why is it not happening all the time?

Inner and outer tie rods are scheduled for install for Tuesday. I will post if that cures the problem. My Burb is 2wd with the same issue so doubtful that the CVs are the issue since my truck doesn't have any

 

[CMoore711]

Inner and outer tie rods are scheduled for install for Tuesday. I will post if that cures the problem. My Burb is 2wd with the same issue so doubtful that the CVs are the issue since my truck doesn't have any

Let us know if tie rods cure you're issue. Mine are not that old; I'm at 136K miles, but I just replaced my tie rods at about 110K, so they don't even have 30K miles on them.

 

[dpollak81]

Just found this and our 15 Denali 8 speed does this too intermittently. We notice it when I go to decelerate from 80 like for an off-ramp example or if we drive over the pass to Reno and are on a downhill slope. Super random and it will happen the first time I apply the brakes and then not again. I thought I might have a really slight warp to one of the rotors that only shows up at high speed or a sticking caliper but again its super random. I've noticed that I get a pretty good low groaning noise if i'm on the brakes hard to slow down from high speed (traffic comes to a sudden stop) like when you have cross drilled rotors or something. Ours is bone stock except I just swapped in the Arnott shocks and struts.

I did just have the tires rebalanced and rotated and I'll test later this week when we head to the bay area. I can stop from 65-70 no problem but if i'm up towards 80-85 I'll get the shake.

 

[CMoore711]

@fozzi58 If new tie rods doesn’t solve the issue for you I’ll be directing my efforts to further inspect the Steering Intermediate Shaft and/or Steering Gear Assembly.

When I go over bumps my front end has play and it feels more horizontal, left to right. This is without applying any brakes.

 

[Geotrash]

My front CV Boots are leaking a little grease; I'm not sure if the CV Joint is actually bad or failing, but the boots are leaking a tad. Could failing CV joints be causing this issue? If so why is it not happening all the time?

This is very common in other makes. On Hondas, it's the inner drivers-side CV joint that leaks grease out and the joint starts binding up intermittently, shaking the steering wheel like an unbalanced tire. I had an Acura Legend that I put 2 rebuilt CV axles on the driver's side before finally buying a newly manufactured part from raxles.com. The original axle developed the shake after leaking out some of the grease, and the rebuilt shafts were no good either. It drove me crazy until I finally figured out what it was. The raxles shaft was perfect and solved the problem. That said, mine was most pronounced under acceleration, but could be felt while coasting and braking as well.

 

[fozzi58]

New tie rods - inner and outer installed. Same issue with the shaking so this did NOT resolve my problem.

My mechanic wants the whole kit replaced. Not just having the calipers rebuilt like Wilwood has offered, because he is concerned there may be a possible issue with the rotors or bearings that can't be seen while the truck is in the air on a lift. He suggested I go back to OEM front brakes if Wilwood doesn't do something.

I sent a long winded email to Wilwood pleading with them to send me a replacement kit, I would pay for shipping both directions, and even put the kit on my CC until getting credited back when I send back the old kit. My mechanics been over everything in the suspension, front and rear, did another brake flush, mic'd the rear brake rotors again, checked to make sure there was no issue with rear brakes. The truck is mint as can be for 80k miles. Either that or order another kit and then dispute the charges. Not sure I want to go either of these routes.

That being said, if Wilwood doesn't do something for me other than offering to rebuild the calipers, I will be relentless in leaving negative posts about this experience. I went with Wilwood because so many hot rodders have said positive things about their brakes and their customer service. I guess there is something to be said about 90% of OEM BBKs being Brembo.

 

[CMoore711]

I'm just not convinced that it's the Wilwood brakes... I do not experience the front end vibration/shaking every time I apply the brakes, it's intermittent, it comes and goes. Some times I come to a complete stop as smooth as can be, like it should. Other times it shakes/vibrates pretty bad.

@fozzi58 you had mentioned similar operation in your OP. If it were in fact the brakes wouldn't you think that the vibration/shaking would happen every time you applied the brakes? How's come sometimes when you (we) come to a stop it's smooth and operating at it should? Which is the same for me to BTW.

Now what I have been noticing more and more lately is that I have some shaking from the front end when going over sharp bumps; Sharp as in sewer or drainage lids and immediate change in road height. It's more left to right horizontal movement. I don't notice it in just more smoother humps or gradual incline decline changes in the road. Additionally, after the bump there's almost a sort of "after-math" vibration/shaking of the front end. Almost as if my front end has to "recover" from the sudden bump/change in road height.

 

[fozzi58]

I don't disagree - I would think that if it was a braking issue it should be every single time I apply the brakes. That's my logic kicking in. But my mechanic explained it that since you have 6 pistons, lets says the center one has a seal that has jumped the gap, or the cylinder is scored, its going to be an intermittent issue. The piston may not be getting stuck in the open position because there's enough travel or force that pops the piston back into the sleeve without it keeping the piston engaged. But because the seal is possibly ruptured or some other issue, it doesn't engage smoothly all the time. He's guessing based on his 30 years of experience but he's reluctant to open up the calipers himself and he still things Wilwood should be responsible since this started happening 3 months after installation. And yes I had him check the torque on the bolts between the rotor and the hat.

In my case it doesn't matter the speed or the amount of pressure on the pedal I apply, I will get that pulsating feedback intermittently. Sometimes - its smooth as glass, even a hard stop at 60mpg and other times my big fat ass is getting shaken front to back from a mild stop at 30mph.

I had a dealership do a brake diag just to get a 2nd set of eyes on the issue and immediately they said rear brakes are the problem 99% of the time with what they diagnosed. After I explained I'm on my 2nd set of calipers and 3rd set of rotors and pads they kind of relinquished that its probably not the rear brakes, especially after inspecting the OEM calipers which I still have. I highly doubt that my oem calipers and then a 2nd set of aftermarket rear calipers would both be bad along with stop tech rotors and pads and then a whole powerstop kit. Then again, if it wasn't for bad luck, I'd have no luck at all.

This sucks cause I have been wanting to hit the autocross with this thing since the season opened but its annoying to drive as a daily...I can't imagine how bad this would be trying to do stop-go-stop on a track.