What the hell is this noise?

Ok, so my truck literally just broke 300 miles today. During those 300 miles it has been babied, with hard acceleration maybe 3 times at most.

Anyway, I've noticed that about 30-60 seconds after I crank it up for the first time every day I hear this noise coming from the rear....it sounds like tiny pebbles being thrown up into my fender wells. I know that it's not road debris, because the roads are clean and it happens like clockwork each day. Every single time it happens it's at the stop light at the end of my subdivision. I have no clue if it does it after the vehicle is warmed up because at that point I'm normally playing music.

I attached a video which hopefully allows you to hear it. It's at the very end of the vid, so you can ignore the first 3/4. Anyway, what do you guys think it is?

 

I think it sounds like a trip to the dealer. Anything in the bed rattling around?

 

Nope, nothing in the bed or the compartments.

 

Does it make the noise when you are just rolling?......the noise seemed to occur when you let off the gas.

 

Can you turn down the freedom rock and re-create the noise elsewhere or more often?

 

Not when rolling for any length of time that I have heard, it does only seem to happen right after I let off the gas - and not if I apply brake.

 

Freedom rock?

 

You said you hear it at the same spot every time and by the time you leave you have your music on..was a joke about music, but being serious about re-creating the sound elsewhere and more often.

 

Oh, lol.

I'll try. The problem with recreating is somewhere else is that there is only one way out of my subdivision, and it doesn't seem to happen after the truck warms up.

I'll play around tomorrow and see what I can do. In the mean time, any speculation?

 

I worked for GMC/Honda as a ASE Technician for 9 years, and from the sound, I would have to re-create it to give some kind of answer.

My first suspect would just be road to tire noise. I have a box with 9 inputs and 9 wires you can clamp on various parts of a vehicle and it comes with headphones, and basically you change the dial to the wire you want and try to pin point the noise according to were you placed the wire, most dealerships have these.

Like I said my first instinct without re-creation is tire to road noise, almost like when you go from blacktop to gravel packed concrete roads.

 

does it happen only when you start driving and only during deceleration?

 

Other members had similar problems....someone replaced a driveshaft or greasing slip joints. either way, that new i'd take it to the dealer and see if they can help and hope their techs are worth a damn.

 

You could easily check the drive shaft / U-Joint, by getting underneath the truck and physically trying to wobble the joint's in the drive shaft.

When someone complains about noise from under carriage when letting off the accelerator or hitting the accelerator this usually points towards a U-Joint / Drive shaft due to the torque being applied or let off.

 

Only during no-brake deceleration....free wheeling I guess you'd call it.

 

Ah, well if no pressure is being applied to decelerate the vehicle or speed up then you can probably cut the drive shaft out of the picture of problems.

 

I'll get under her tomorrow and poke around. Seems like it if were the u-joints or drive shaft I'd have some driveline vibe at some point, but I don't. Very strange.


I'm tempted to just let it ride until something eventually breaks (I have the extended warranty), but then again I'd rather not screw something else up in the process if it's a crucial component.

 

Hopefully this isn't a drive-shaft vibe issue, but it appears to do it after you let off the gas. Either that or something isn't bolted down. Do a once over and check your glove box and cubbies for anything the dealer might have left loose like the bed cleats or plastic dealer prep items. If it is nothing you can see to save a trip to the dealer then by all means call it in.

Edit: I only say this because I've had a bad u-joint with no vibes in the steering wheel and it made a sound very similar to this when not under load.

 

Well like I posted a second ago, if you are not applying any torque against the shaft and its just during free wheel, try this....when you left off the gas put your truck in neutral and coast and see if you hear it.

 

Are there chains or anything like that in the rear diff?

It sounds very familiar to a noise I used to hear on one of my racing bikes if you pressed just a little to hard on the gear shifter getting into neutral....like the gears were trying to "find" each other so they could spline. Hell I have no clue, but it definitely sounds like two metal pieces grinding/sliding together.

 

Cool thanks for the info. I'll look around and see what I can find.