Braking

Dmendrin · May 8, 2014

I have a couple of question to see if anyone else is having these issues. The dealer is stating that no issues are found but clearly its something unless we all have the same issue. On my 2014 Silverado LT my break pedal is now squeaking when I apply pressure to break. I can feel with me foot a spongy feeling as well. It doesn't feel right at all. Also else having this issue? Also when coming to a stop or at slow speeds in traffic on and off the gas and break ill hear from time to time (at least 3 times a week) a thud in the trans and jerks the truck. I know everyone will say take it in. I have and they couldnt get it to happen after burning a full tank of my own fuel. Anyones help or direction will be awesome. Thanks.

Jon Rogers · May 8, 2014

I'm not have any issues with my brakes.

fondupot · May 8, 2014

ahem.....brake.....braking.....brakes.

That being said. I have not experienced this issue. My brakes feel normal and my pedal does not squeak. Perhaps you can apply a bit of grease to the pedal mechanism to try an eliminate the squeaking.

And about the thud you are experiencing. With trucks having a leaf sprung rear end, the rear drive shaft needs to be able to slide in and out of the of the transmission housing. As the suspension goes through its range of motion, which on a pickup truck is quite large. The drive shaft needs to lengthen or shorten slightly to accommodate the rear axle going up and down in its suspension travel. This is called a slip yoke. In traffic where you would be on and off the gas and brakes, it is common for the slip yoke to make a bit more noise than normal.

If it really bothers you, I would take it back to the dealer and ask them to re-grease the slip yoke because you are experiencing a lot of slip yoke noise.

Any pickup truck I've ever driven has had that characteristic. The only way to totally eliminate slip yoke movement is to install a slip yoke eliminator kit. Which I do not believe is available for the new trucks. Vehicles with independent rear suspension do not have this characteristic because then the drive shaft is fixed between the rear diff and the transmission.

glioma · May 8, 2014

"Breaking"?

The curse of the English language.

thewhitestallion · May 8, 2014

"Breaking"?

The curse of the English language.

now that right ~~their they're~~ there (damnt!) is funny!

Dmendrin · May 8, 2014

Geeez I feel like a idiot. I should drink a cup of joe first. Dumb award goes to me for the day. And thanks for the info fondupot.

GMCustomerService · May 10, 2014

Hello Dmendrin,

I see that your fellow forum members have provided you with lots of advice. I might not be able to provide you any technical support but if you have any lingering questions or concerns please contact me via private message. I would be happy to assist!

Jennifer T.

GM Customer Care

2strokesmoke · May 11, 2014

Geeez I feel like a idiot. I should drink a cup of joe first. Dumb award goes to me for the day. And thanks for the info fondupot.

What you are feeling I believe is.

Your truck shifts up through the gears very quickly as you accelerate, and if you have to come to a stop very quickly the transmission has to downshift very quickly too!

Now here is where it goes wrong, the tranny is shifting down a gear or two that brings up your engines rpm and torque and your attempts to stop this force makes your brakes feel less effective during this particular time.

Your brake's pedal force might feel somewhat soft or less effective, followed by the drive shaft thunk that most feel when they have to stop fast, or quick throttle and quick release of throttle with current gear at top of it's rpm range.

This thunk is what engineers and mechanics might call axle wrap! Torque from engine and a gear at it's high rpm range and sudden brakeing force only results in something has to give.

Rear axle pivots forward large amount of energy is released, causing the leaf springs to thunk up against each other, or drive shaft forward thunk what some call slip yoke noise. The real problem GM keeps making there leaf springs lighter and more flexible allowing the leaf springs to absorb road energy for comfort, at a price of axle wrap energy transfered to suspension components.

A toyota mechanic was very adamant in fixing this problem on his customers light trucks and found that clamping a small leaf plate and a set of ubolts together forward of the rearend 2" eliminated the known axlewrap thunk.

I know this worked for the 2013 sierra and silversdo. I have not tried it for the 2014's, this fix preloads your rear leafsprings somewhat removing most of this daily thunk you would feel while stopping quickly.

GM needs their transmission's to down shift very quickly allowing the transfering of this energy to the suspension without mechanical weaknesses and noises of energy release to truck.

a forward facing tuned shock would remove this axle wrap like what is on large monsters trucks at shows.

just my 2cents worth.