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HELP! Weird intermittent popping sound after 25 mph.

GoeHaarden

Full Member
Joined
Jan 9, 2019
Messages
10
Long time lurker, first time poster here...Thanks in advance!

So, I will attempt to describe this noise the best I can...

2002 Chevy Avalanche Z71 with ~180k miles. Stock.

It started about a month ago and it kind of sounds like popcorn (honestly), very irregular in pattern and loudness. It's seems like it's directly in front of the driver seat/steering wheel in the engine bay, and maybe slightly mid-line. It's really intermittent and kind of chaotic after 25 mph, but once I hit about 45 mph it gets more regular but less intense and almost seems to disappear after 70mph. Hard to tell with wind/traffic noise though. At higher speeds, the pitch kind of changes from a popping to a ?sputtering? almost. It used to go away when the drivetrain was warm. Like if I drove for a while, parked, and then drove again it wouldn't do it. Now it doesn't matter

When it happens:
- After ~25mph, gets more regular and less intense as speed increases
- Turning and driving straight
- Accelerating and decelerating

It does not happen when stopped, and revving the engine. So, I've eliminated the motor as a possible cause. I don't think it's the exhaust either since the vehicle has to be in motion. At first, I thought it could be a shock sticking as it was pretty irregular, but I don't think that's it anymore as it has gotten more regular. I do have a little side-to-side play in my front wheels when the Ave' is jacked up, so I know I need new tie-rods but I don't think this would be the cause of this noise. No up-and-down play in the wheels though. It does not effect vehicle performance, but it's just really annoying and I don't want something worse to be looming.

I'm not sure if it matters, but I had an antifreeze leak for about a year until I recently found the source (heater core disconnect) and fixed it. Also, I was changing my oil last week and I noticed that the area around the front differential oil drain plug looked moist. So, I changed the front diff oil as well and there was almost no torque on the plug when I drained the old oil. Kind of scary. I was hoping it may have been low diff oil, but that was not the case.

I did search the forum and the threads I found that may sound similar are very old and don't come to a resolution...

I'm not a mechanic so please correct me if my assumptions could be wrong. Thanks again!
 
Perhaps the intermediate steering shaft?
 
EXT4ME said:
Perhaps the intermediate steering shaft?

Thanks for the reply. The noise happens when going straight and turning, so I wouldn't think it would be related to steering but I'm open to any suggestions. Is there anyway to test the intermediate steering shaft and see if it's bad?

 
There are many Youtube videos describing the noise and some fixes.

I did a quick search and this one demos the sounds this guy was hearing.

I am not sure if that is the sounds you are hearing, but this is a common problem with these trucks.

The sound on mine happens when driving straight ahead and sometimes in turns.

I plan to replace both the steering shaft bearing and the intermediate steering shaft this spring.

There are many videos describing these fixes.

Some say just applying lube will take care of the problem, but I am going to change out the suspect parts since my truck has over 225K miles on it.

The lube sounds to me like a band-aid fix for an older truck.
 
EXT4ME said:
There are many Youtube videos describing the noise and some fixes.

I did a quick search and this one demos the sounds this guy was hearing.

I am not sure if that is the sounds you are hearing, but this is a common problem with these trucks.

The sound on mine happens when driving straight ahead and sometimes in turns.

I plan to replace both the steering shaft bearing and the intermediate steering shaft this spring.

There are many videos describing these fixes.

Some say just applying lube will take care of the problem, but I am going to change out the suspect parts since my truck has over 225K miles on it.

The lube sounds to me like a band-aid fix for an older truck.

Gotcha. That sound is a lot different than what I'm experiencing. Thanks though.

I just found a video that is pretty close and now I'm thinking it may be a bad CV joint. I'm not sure though, as I thought CV joints usually make noise while turning if bad. I did just find this video https://www.youtube.com/watch?v=j0pEp3yVS4o and the sound is pretty spot on, but again mine makes it almost all the time after 25mph+ regardless of turning/accelerating/etc.
 
Gotcha.

Mine did that a long time ago and I replaced both sides at the same time.

That took care of that noise and it then was off to chase others.

(y)
 
Did you install a bug deflector about the same time it started?
 
ItsStopher said:
Did you install a bug deflector about the same time it started?

Nope. I did find some threads talking about this, but I just have the wind deflectors on the side windows that have been there since I bought the truck 5 years ago. They're all solid.

***************
EXT4ME said:
Mine did that a long time ago and I replaced both sides at the same time.

That took care of that noise and it then was off to chase others.

I got to thinking about the CV-joints and it seemed all the videos I found were from front wheel drive cars. So their CV joints were under load when it was making the noise. So today I decided to put the truck in 4-Hi and do a loop around my street. At very low speeds I had intense popping coming from the driver side front wheel while turning. Which only further supports my bad CV-joint theory. I think I'm going to replace both...
 
GoeHaarden said:
I got to thinking about the CV-joints and it seemed all the videos I found were from front wheel drive cars. So their CV joints were under load when it was making the noise. So today I decided to put the truck in 4-Hi and do a loop around my street. At very low speeds I had intense popping coming from the driver side front wheel while turning. Which only further supports my bad CV-joint theory. I think I'm going to replace both...

My EXT is AWD, so the CV joints are always under load.

Maybe that's why I heard them before they totally came apart.

I had both front axles replaced at 150K miles.

I had both front hubs replaced at 123K miles.

All of these, and other things, were changed while I was chasing front end noises.

Each thing changed reduced the amount of noise coming from the front end of my EXT.

It wasn't until a set of new tires, replacing a set of E-Series tires that came on the truck, and having the front diff rebuilt, did I finally call this project over, for the time being.

I wore that set of tires out since then and I have replaced them with the same type, because I liked how quiet they are.

Fast forward to just a month ago with another 70K miles on the truck, did I finally spring for a brand new OEM transfer case.

Now, everything is finally quiet like I wanted.

(y)
 
EXT4ME said:
My EXT is AWD, so the CV joints are always under load.

Maybe that's why I heard them before they totally came apart....

I had no idea that the Cadillacs were AWD. That's awesome.

I just changed my brakes like two weeks ago (noise was happening before), and I should have done the hubs while I was in there. I wasn't thinking about it, and still trying to diagnose this thing.  Hopefully replacing the axles is going to fix it.

Like you said though, probably off to chase another noise anyway...lol
 
So, I changed the driver side CV-axle and the noise persists. Looked at the front drive shaft U-joints but they seem solid. Not really sure where to look now. Also, it has developed some kind of whining noise as well.

Would it be ok to remove the front driveshaft, and drive the truck? I know I would lose 4wd, but I don't ever use it except in a pinch.
 
GoeHaarden said:
Would it be ok to remove the front driveshaft, and drive the truck? I know I would lose 4wd, but I don't ever use it except in a pinch.

No.
 
EXT4ME said:

Just to be clear, I'm talking about the drive shaft from the transfer case to the front diff. Its bolted to the front diff, but has a slip yoke on the transfer case. So it spins all the time in 2 wd, but it's not under load until the front diff engages 4wd.

Is it because the transfer case will leak oil without it, or is is bad for the truck? I'm kind of assuming that the front diff is gone bad and I dont want to spent $2g to fix/replace. Truck is too old to dump that kind of money into and Id rather just lose 4wd
 
I will retract my no in your case and let someone with better knowledge of the 4WD systems assist you.

I know for a fact, that in my case, with the All Wheel Drive, you can not remove any drive shafts and operate the vehicle since that will destroy the transfer case viscous coupler.

Pardon the interruption and carry on.

Best of luck with your repairs.

(y)

 
EXT4ME said:
I will retract my no in your case and let someone with better knowledge of the 4WD systems assist you.

I know for a fact, that in my case, with the All Wheel Drive, you can not remove any drive shafts and operate the vehicle since that will destroy the transfer case viscous coupler.

Pardon the interruption and carry on.

Best of luck with your repairs.

(y)

Lol. No, thanks for your help. I'm just getting mixed info from doing searches and I'm not a mechanic so I'm in a pickle here...
 
Is there any difference in sound when going in reverse?
 
ca2kjet said:
Is there any difference in sound when going in reverse?

Well, actually lately when reversing out of my somewhat sloped driveway that popping happens at low speeds. Other than that I don't know as I don't reverse much other than that. I'll try an empy parking lot pick up some speed in reverse...
 
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