What is that noise!!??

OK, I've got an '02 Silverado 1500HD Crew Cab 6.0L. 74,500 miles. This is a hard one to explain in words rather than actually hearing it by ear but I'll try my best. At times while driving there will be a light "whistle" or "squeal". I'm comparing it to the sound you would hear on the old v-belt set ups like when you had a loose Alt. or PS belt you would have that "sceetching" sound. It's similar but NOT NEARLY as loud. It seems to only happen sometimes while accelerating from a stop for only 2-4 sec. then gone and does not happen while at highway speed. There is no vibration and it seems to have no ill-effect on the way the truck drives or runs it's just the noise but it drives me nuts. I'm going to start with the u-joints and hanger bearing since this truck did have a fifth-wheel in it at one time and those tend to wear faster from pulling and then check my belt and pulleys up front. I think I'll be starting in the right areas.

Any suggestions on other possibilities?? Thanks.

if it is the belt noise it is possible the idle pulley or the other pulley bearing is making noise....I have had this bearing make noise since 2000 but only when its cold...after the weather warms it doesn't make any noise..

to find out if this is the problem remove them,one is reverse thread stud, and lube the bearing..it will not make noise for a while ..then you'll know..which one....

I believe they cost 20.00 ea..

start with checking belt tension marks on the tension pulley. it'll tell you if the belt is, actually, overstretched, or not.

I had a problem very similar to this when my truck had only 6,000 miles on it. Took it to the dealership and they said it was a dirty belt. They cleaned it and sent me on my way. 10 miles later I arrived at home just to hear the same noise. It sounded like a loose belt but not quite as loud. After 4 trips to the dealership, 2 new serpentine belts, 3 belt cleanings, and about 20 days worth of time at the dealership they found the problem. They said is was a bad front drive shaft seal. I have no idea how this made this awful noise, but they fixed the seal and I have never heard this same noise again. I now have 105,000k on the truck.

start with checking belt tension marks on the tension pulley. it'll tell you if the belt is, actually, overstretched, or not.

I never seen any of these type of belts stretch,,,but I have seen many belts of the wrong size used....the part stores screw this up often...and as you stated it is important to check the tensioner marks for proper alignment ...as well as the proper width...

the belt cleaning is a way to determine if oils are contaminating the belt...washing the belt with a dishwashing soap will remove the oil's if any safely...

I still believe the pulley bearings are the problem ...this is very common on this vehicle ...its a very low quality part..

I'm going to replace the belt this weekend. It looks like the original belt and 74,000 miles is enough for a new one. While I have it off I'll remove the tension pulleys and spin and inspect them by hand. I did notice when I bought this truck a few weeks ago that the dealership had pressure washed or steam cleaned the engine and everything under the hood as usual. Maybe whatever they used contaminated or left a residue on the belt system. If that's not it I'll move on to the driveshaft. It's just not a noise that I've EVER heard anything in the drivetrain system on a vehicle make before, but you never know....

I'll update my findings as I go....Thanks for all of your input!

I'm going to replace the belt this weekend
Make sure you give all the pulleys a once over to degrease them while you have the belt off!

I'm going to replace the belt this weekend. It looks like the original belt and 74,000 miles is enough for a new one. While I have it off I'll remove the tension pulleys and spin and inspect them by hand. I did notice when I bought this truck a few weeks ago that the dealership had pressure washed or steam cleaned the engine and everything under the hood as usual. Maybe whatever they used contaminated or left a residue on the belt system. If that's not it I'll move on to the driveshaft. It's just not a noise that I've EVER heard anything in the drivetrain system on a vehicle make before, but you never know....

I'll update my findings as I go....Thanks for all of your input!

do not throw away the old belt...keep as a back up and if necessary a reference for getting another belt...use the belt info stamped on it to cross over the correct belt....get the belt length and width as the belt now has,,,and compre with new,,,this may be different....

Replaced both the main and AC belt this weekend. Both the tension and idler bearings were good. Cleaned all pulleys with a good degreaser. The entire belt system is much smoother/quieter now. However, after taking it for a short drive I still heard the same noise one faint time...:confused: I'm going to look into the hanger bearing. Maybe it's just starting to get dry or something. The strange thing is now that I think about it whenever the noise is there it seems as though I'm getting into the accelerator while making a turn.

:2cents:Replaced both the main and AC belt this weekend. Both the tension and idler bearings were good. Cleaned all pulleys with a good degreaser. The entire belt system is much smoother/quieter now. However, after taking it for a short drive I still heard the same noise one faint time...:confused: I'm going to look into the hanger bearing. Maybe it's just starting to get dry or something. The strange thing is now that I think about it whenever the noise is there it seems as though I'm getting into the accelerator while making a turn.

since you replaced belts and disturbed the idler's,,now the noise has changed/lessened...this I would again suspect the idler /pulley bearing..

when it starts making noise get some spray lube with a long spray straw and spray the bearing area.when in operation..when the noise stops then you have found it..

the high pressure washer will force water and any cleaner that is used into a bearing,also some grit as well.

the high pressure washer will force water and any cleaner that is used into a bearing,also some grit as well.

use of a high pressure washer is as you stated is a way to damage the engine mounted equiptment.

the use of a pure steam washer , no chemicals, with the pressure reduced is what I would use prior to engine , equiptment overhaul...

on this engine the ks under the air intake is at risk of damage as well..

the dealerships will clean the engine area to get it clean as most people look for oil leaks ,coolant leaks ,as well as how clean the motor area is when looking at a vehicle to buy.most of the time they use a high pressure washer with in line bottle of degreaser and most of the people that are doing the cleaning will not try to keep the spray away from the bearings.one other thing is a u-joint that has a cup getting dry will make a slight squeal when taking off from a stop. had one on a '74 roadrunner that did this and like to have never tracked it down.it would make the noise then quit making it until the next stop-take off.most of the factory u-joint and alot of the replacement u-joints do not have a alimite so you can grease the u-joint.

I think I'm going to drive it for a while, then replace the u-joints, I did notice the end caps on them have a little surface rust so the cups probably are getting a bit dry. Not sure when I'll get around to it, but I'll post my results when I do...

Thanks.

I think I'm going to drive it for a while, then replace the u-joints, I did notice the end caps on them have a little surface rust so the cups probably are getting a bit dry. Not sure when I'll get around to it, but I'll post my results when I do...

Thanks. when you feel vibration when you take off or slow down might ought to see if you can shake the u-joints as if the cups are dry it won't take much longer to chew the needle bearing up the it will chew on the cup then it[driveshaft ] is outta there. no chance of them having an allimite to grease them with. is it true as they say fargo is one of the coldest places in the u.s.?:runaround:

No, there's no grease zirc on them of course. The weird thing is there is no vibration or anything like that it's just the strange noise. The ds and all the joints seem pretty tight. There's no clunk or anything like that when shifting. The only play anywhere is around the hanger bearing but I believe there should be some "movement" there due to the rubber grommet that surrounds it. Am I correct? I'm going to moniter the noise for a few weeks or so then put new joints in and see what happens.

As far as the temps. I think the only place colder in the country is northern Minnesota. Yesterday morn. where I'm at, neg.19 F. ....Weatherman says 30's and 40's next week, spring's on the way!:biggrin:

yeah the rubber grommet will give some and you can see it give. most of the factory u-joints and even tierod-ends ,balljoints,steering links don't have anyway to grease them.some of the replacement s for them don't have a zerk or allemite in them. we think we got it rough when it gets down to 20 degrees down here.we used to live up north as my dad used to build the power lines from poles to the high voltage towers and we moved all over .i remember when we lived in ohio we set traps when the temperature was 20 below zero with a wind chill of -40 .i don't think i could take it now.