Brake hard, stop..let off brakes...CLUNK.

[Danneman]

Hello gentlemen - long time lurker, first time poster. Great forum!

A riddle for the gurus out there…..99 Yukon SLT 4WD, 113K, overall great runner and well cared for. Cruising along at let’s say 30-ish, decent around-town speed. Hit the brakes hard - doesn’t have to be an emergency stop, just harder than you normally would if you were rolling up to a red light and gave yourself plenty of time to slow down smoothly and gradually. Come to a complete stop, sit there for a second (or don’t, it doesn’t matter actually), then let off the brakes - CLUNK. Happens just as soon as there is any forward motion following that hard brake, not once you hit the gas or anything…you brake hard > stop > sit with brake pedal depressed for any period of time > let off brake to roll forward, and immediately…bam. Doesn’t happen again unless you get up to speed and brake hard again.

Feels like it’s beneath me or perhaps just a little forward of me, can’t tell exactly. Varies in magnitude, but generally the harder you brake from the higher the speed, the bigger the clunk. Braking lightly and gradually….doesn’t happen, ever.

The best master tech that my local GMC dealer has says he can’t find anything wrong - and we replicated the issue on a ride together, he knows what symptom he’s trying to diagnose…but he can’t diagnose. Can’t find anything that would explain it. BUT, he is also massively busy b/c he’s apparently the only decent tech they have, and he had the flu the day I came in with this one, so he probably didn’t really give a $*#&.

Sorry for the long post! Just wanted to give y'all something to work with. I’m interested in any and all thoughts on what might be going on, but I’m particularly interested to know whether anyone has had this exact same issue and knows what the deal is. Anyone seen this before?

 

[about20ninj45]

Hello gentlemen - long time lurker, first time poster. Great forum!

A riddle for the gurus out there…..99 Yukon SLT 4WD, 113K, overall great runner and well cared for. Cruising along at let’s say 30-ish, decent around-town speed. Hit the brakes hard - doesn’t have to be an emergency stop, just harder than you normally would if you were rolling up to a red light and gave yourself plenty of time to slow down smoothly and gradually. Come to a complete stop, sit there for a second (or don’t, it doesn’t matter actually), then let off the brakes - CLUNK. Happens just as soon as there is any forward motion following that hard brake, not once you hit the gas or anything…you brake hard > stop > sit with brake pedal depressed for any period of time > let off brake to roll forward, and immediately…bam. Doesn’t happen again unless you get up to speed and brake hard again.

Feels like it’s beneath me or perhaps just a little forward of me, can’t tell exactly. Varies in magnitude, but generally the harder you brake from the higher the speed, the bigger the clunk. Braking lightly and gradually….doesn’t happen, ever.

The best master tech that my local GMS dealer has says he can’t find anything wrong - and we replicated the issue on a ride together, he knows what symptom he’s trying to diagnose…but he can’t diagnose. Can’t find anything that would explain it. BUT, he is also massively busy b/c he’s apparently the only decent tech they have, and he had the flu the day I came in with this one, so he probably didn’t really give a $*#&.

Sorry for the long post! Just wanted to give y'all something to work with. I’m interested in any and all thoughts on what might be going on, but I’m particularly interested to know whether anyone has had this exact same issue and knows what the deal is. Anyone seen this before?

I had that symptom once in my 99 jeep. Turns out they installed the anti rattle clips incorrectly and the clunk doing I was hearing sounding like binding of gears, which turned out to be the clips broke the pad and was also binding in the rotor, hence it only happened after brake engagement

 

[Kpwweb]

Classic case and mileage of driveshaft slip-joint clunk. Not a huge deal. The slip-joint splines just need to be greased... Either at the back of the tranny (for one-piece driveshaft) or at the slip joint (for two piece).

Have the tech grease the driveshaft slip-joint splines.

 

[Danneman]

Super helpful, thank you so much! That's all I needed to feel like I can go to a dealer armed with a little more information. It's amazing, I could build you a house, a boat, a custom guitar, a circuit board, all from scratch...but I don't know jack-all about cars. Talk about feeling powerless. Thank God for forums like this and kind people such as yourself.

 

[SunlitComet]

if the yoke greasing keeps letting you down then you will need the new yoke design.

 

[Danneman]

Took it in today to a new dealer. They replicated the issue easily, cautioned against being too anxious and throwing parts and money at the problem, recommending instead that while it could be the slip yoke and they'd be happy to go ahead and lube it today, there are some bushings all around starting to wear that could also be part (or all) of the problem so we could try coming in one day, lubing one area, seeing how that goes...if it doesn't work, try another, etc....but having what sounded to me like consensus (incl. other opinions I've gathered) that it was the slip yoke I said yeah let's go ahead and lube today, see if that helps, if it does we know we've isolated the problem, if it returns we'll change the yoke out for the new one, and I was quoted 500ish for the parts and labor on that.

The lube did it - drove it home completely clunk-free. And I might be imagining things but the drive felt a little "tighter" all around.

Thanks again fellas!

 

[SunlitComet]

what bushings you talking about? if you need the improved yoke get it from http://www.fortwayneclutch.com/. tell them you need the nickel plated one discussed in the tsb.

 

[Danneman]

what bushings you talking about? if you need the improved yoke get it from http://www.fortwayneclutch.com/. tell them you need the nickel plated one discussed in the tsb.

The bushings he was pointing to were in the front end...on the sway bar, the lower control arms, etc. He wasn't necessarily saying those were causing the problem, you could tell he thought the slip yoke was most likely the issue, I think he just wanted to make sure (especially as I was a first time customer there) that I understood that there was wear in various places and that it could be causing me to hear/feel this or that. I don't know, it was a little odd I guess, but I assume he was just trying to give me the sense that he doesn't just want to go replacing something I said to replace and spend my money without me really having the full lay of the land - which is nice.

 

[Danneman]

what bushings you talking about? if you need the improved yoke get it from http://www.fortwayneclutch.com/. tell them you need the nickel plated one discussed in the tsb.

PS thanks for the yoke source, I forgot to say that!

 

[SunlitComet]

very well.