growlin' noise

[trailburner]

i get a growlin' noise on deceration. whether it's in gear or not. it goes away on acceleration. this happens at any speed but most noticable around 50 mph. doesn't effect drivability at all. also the gas pedal "buzzes". don't know if it's related or normal.

does anyone have any idea where to look first before i have the thing scattered all over my barn lookin' for a noise?

thanks in advance!

[Wahugg]

When we picked up our new Silverado back in 2010 it did this. No noise when accelerating. but a howl/vibration was present while coasting or when a negative load was put on the drive terrain such as engine braking while towing a trailer. Turned out it was improperly set up gears in the rear differential. Gm gave us a whole new axle with labor for free.

Check your rear diff fluid level and magnet for metal particles. While your at it check your Transfer Case levels. If the fluid is low then you may have toasted a bearing in there. Also as roadie always says, make sure the T-Case fluid has been changed every 50k.

Other things I think it could be are a bad bearing or possibly bad/loose U joints.

Good luck,
-Wahugg

[navigator]

that is your dog in the back mad because you are slowing down
my first guess is you have a hub/wheel bearing going bad.
Can you give us an idea of where the sound is coming from?

[trailburner]

thanks! i haven't quite pinpointed the noise yet.... but i'm leanin' toward the back. i just got this thing a month ago so i have no idea what it's been through. i'm guessin' hell and back by the smells that come out of it on a hot day!
what wahugg says sounds exactly like what i'm experiencin'. i'll look into it and check the fluids. i'm guessin' the dealer topped off all the fluids, but it should still show some color in the oil. i was gonna put in a posi unit EVENTUALLY, but that might come sooner than later. it'd be really nice if it was just a u-joint or a bearing.

thanks again....... i'll update the thread when i learn more.

.........if my noisey coonhound was in the back hollerin', i wouldn't have noticed the noise to start with!!!

[Wahugg]

If you just picked up your tb it's CRUCIAL you check the following fluids:

Transmisssion- 100k normal service life (50 if in extreme conditions)
Front Diff- assumed 50k
Rear Diff- assumed 50k
Transfer Case- EVERY 50k (other wise you run the risk of burning up the clutches)
Engine oil- When ever your DIC or "Change Oil" Light pops up. No need for every 3k or 4k anymore with today's technology.
Coolent- Every 100k

It's also worth mentioning that you should change your spark plugs at 100k with ACDelco 41-103 Iridium Spark plugs. Any other kind tend to cause problems such as misfires. Your throttle body should also be cleaned around every ~30k. Otherwise your truck might stall at idle with the A/C on due to gunk build up on the back side of the plate. When you go to check your differentials for fluid, make sure you can take off the fill plugs before you attempt to take off the drain plugs.

Now, if I had just picked up the truck I would change every fluid from front to back. This way I know everything is serviced and I get to look over the truck in a bit more detail to see if anything out of the ordinary might need servicing. Make sure you don't skimp out on the front diff just because access to it is limited with out taking off the wheel. The internals on it are moving all the time so it's just as crucial to have lubricated as the rear (ask me how I know) and changing the front diff is not easy by any means.

I don't mean to scare your or make it seem like you bought a bad platform, but it's much better to just go over a new truck from head to toe then to allow a problem to develop.

Finally, check your glove box for the RPO code: G80. If you have it your have the only "locker" available for the 8.0'' rear end all I6 SWB trailblazers have. If you want a true locking rear end your going to have to pull an 8.6'' rear end off of an EXT or V8 GMT360 (our platform: Trailblazer, Envoy, Bravida, ect).

-Wahugg

[trailburner]

thanks for all the info, and the ac part number.
i'm a mechanic by trade but have been out of the loop for quite a while due to illness.

i do all the same things you do! i want to know what went into my truck and when it was done..... so i do it. that's the only way to know! it looks like the dealer had the rear diff plug out, but i have know idea of knowin' what they put back in. so i'll pop off the rear diff cover, take a good look at it, and seal it back up. what weight oil is used in the diffs on these things? i ain't had a look in the manual yet.

i have the GU6 3.42 open diff rear. i guess it's an 8inch then. i wasn't sure what the ring gear sizes were on these things. i reckon if i replace this one i'll go for the 8.6... probably out of a junk yard. i have a bad habit of breakin' them so the bigger the better. locking preffered!

i just got back from a ride with EVERYTHING turned off so i could get a good listen. i believe that is where the noise is comin' from. it's not real bad, YET! but it's noticable. i know what to keep my eye on now.

you didn't scare me none... my mom's had one for 7 years so i know they are good trucks!

thanks a lot wahugg!!

[trailburner]

Update on the growlin' noise ....u-joints were absolutely shot! Easy fix. Thanks for the input! Sorry I am so late in gettin' back to you'all with the info.