Deep "Howling, Roaring" sound. Need opinions.

[AndrewG1320]

Just bought a 2006 GMC Sierra 1500 Z71. Fully loaded truck. The only issue I have noticed is a howling or roaring sounds while driving. You can hear it while driving 15+ and hear it more prominently when decelerating and coming to a stop. It is very audible and gets louder as you drive and turn left. Was thinking a wheel bearing because to me it sounds like its coming from the front end. Someone suggested that my differential needs replaced. Truck goes in for an inspection at my local chevy dealer on Monday. Just looking for opinions in the meantime. Thanks in advance!

[davester]

Perhaps if the actuator in the front diff is stuck in the "enabled" position, so the front diff is stuck in 4wd mode (so the wheels are spinning the front driveshaft), it might make that noise, or if the diff is empty of fluid.  It's less likely if the diff is filled and not locked.

 

Easy check if it's locked is to just reach under the truck and try to spin the front driveshaft (with the truck in 2wd).  If you can't spin it, something is wrong (again, most likely it's the actuator in the front diff, but possibly parts are broken inside as well).

 

but front hubs are a good first choice, particularly if the truck is over 150k miles.  Or possibly CV axles, if the boots on them have been damaged so the grease can get out/dirt can get in.

 

And since this is a new-to-you truck, I would suggest

-replacing all fluids (oil, transmission fluid, transfer case fluid, both diffs, coolant, power steering, brake fluid)

-check the brake lines for rust (easy spot to check where they go bad where 4 lines run along the frame from the driver's side front wheel to the abs controller under the cab).  The rear line also tends to rust bad where it runs along the frame above the fuel tank, but it's hard to see there.

-check fuel pressure at the fuel rail on the engine.  Should be right around 60 psi (+- a couple psi), both at idle and when the engine is revved up to 3k rpm.  If it drops and doesn't quickly return to full pressure when the rpm levels off, your fuel pump is going bad...

-depending on mileage, you probably could replace plugs and wires

 

And if you do all that, you probably have too much money, so send me a couple hundred...

[AndrewG1320]

Truck has around 147k miles. The CV axle boots looked to be in good shape. I did test out the 4wd system and it all works, seems kinda loud but works. Is it possible its not fully disengaging when switching back to 2wd? I will see if the front drive shaft is spinning freely in the morning. 

[swathdiver]

47 minutes ago, AndrewG1320 said:

Just bought a 2006 GMC Sierra 1500 Z71. Fully loaded truck. The only issue I have noticed is a howling or roaring sounds while driving. You can hear it while driving 15+ and hear it more prominently when decelerating and coming to a stop. It is very audible and gets louder as you drive and turn left. Was thinking a wheel bearing because to me it sounds like its coming from the front end. Someone suggested that my differential needs replaced. Truck goes in for an inspection at my local chevy dealer on Monday. Just looking for opinions in the meantime. Thanks in advance!

Probably a hub needs changing.  Check out this video, FF to 1:06 and have a listen.  One of our Montana's hubs sounds just like this!

 

 

[AndrewG1320]

Honestly it sounds very similar. It sounds very much like that while turning left at speed. Not that loud going straight, YET. I'm really thinking thats what it is and being that it gets louder as you turn left I would assume its the passenger side. Only thing that made me question myself was when someone suggested the differential gears as I know those can make a similar sounds when making turns when they go bad.

[davester]

If you want to check (after checking that the driveshaft rotates when in 2wd) if it's the front diff, you can just remove the 2 cv axles and drive around a bit with them out.  If you still hear the sound, it's the hubs.    You can also try spinning the axles in the diff and see how they feel/if they make any sound when you spin them.

[dtnel78]

Honestly it sounds very similar. It sounds very much like that while turning left at speed. Not that loud going straight, YET. I'm really thinking thats what it is and being that it gets louder as you turn left I would assume its the passenger side. Only thing that made me question myself was when someone suggested the differential gears as I know those can make a similar sounds when making turns when they go bad.

If you're hearing it while turning or taking curves at left going down the road then it's most likely the right hub. Very easy diy job with metric tools. Don't waste your money at the dealer and get a Timken wheel bearing if possible.

Easy way to check is jack the wheel an inch or so off the ground and grab the top and bottom and push the top in while pulling the bottom out or use a pry bar a couple ft long and put it under the wheel and pry up while resting your other hand at top of tire and rock it as well. If it moves verify whether it's the wheel bearing or ball joint.

You can watch the ball joint while having someone rock it or prying it up and down. Did many of these hubs. Bring a big hammer for removal. IF you need torque specs P.M. me your email Addy and I can send a sheet with them on it to you plus a few other pointers.

IF you're not comfortable doing it you can get it done with the same warranty a dealer would give you at most reputable aftermarket franchise or local repair shops.

They can do fluid flushes as well. 75w 90 on the rear differential. You don't need synthetic unless you want to waste your money.

Check your u-joints as they're known for going bad as well.

Check the differential rear cover for any leaks. IF you see wet fluid and the seal isn't wet then Google GM or Chevy Transfer case "pump rub" or read this article,

https://www.merchant-automotive.com/Transfer-Case-Pump-Upgrade-Kit



Great company. I upgraded the pump 5+ yrs ago and replaced the rear housing as it had rubbed thru. Had the local trans shop check all the gears and they threw a clutch pack in the transfer case. IF you have auto setting for the transfer case then never use it as the clutches slip and wear faster vs using the 4hi when needing 4wd in snow / ice such as what I use it for here in South Dakota.

For the transfer case fluid use the GM stabilitrak as they have friction modifiers in it. Transmission shop even uses it on the 01-06 year models. Most reputable parts houses will sell the GM fluid as well if they don't have on floor just ask.

Go thru and check all the other suspension parts while you're at it and if the front shocks look worn then replace them. The rears are a different story so check what you have and the cost of them as mine are the premium ride and cost at least a few hundred each. Yes it's a Tahoe but same platform in many ways when it comes to the frame assembly.

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[davester]

...just a not on dtnel78's post, "Check the differential rear cover for any leaks. IF you see wet fluid and the seal isn't wet then Google GM or Chevy Transfer case "pump rub" or read this article," 

 

It should be:

Check the transfer case rear cover for any leaks. IF you see wet fluid and the seal isn't wet then Google GM or Chevy Transfer case "pump rub" or read this article,

 

You can also get a much cheaper pressed-metal plate instead of that billet pump, and it works just as well.  You want to either check with the previous owner if one of the fixes has been installed, or crack it open and install one, as when the pump finally rubs through, the TC fluid comes out while you are in motion, and doesn't leave a puddle under the truck, so you notice the problem when the TC is making noises indicating it wants to be rebuilt (much more expensive).

 

And, while pulling on the front wheels at 6&12 and having movement in the hub indicates the hub is bad, it can still be bad/making noises even if it doesn't show any movement.