Noise from the rear end???? Help!!

[Kitchen363]

I've got an noise comming from the rear of my 2002 2wd ext.cab Silverado.

Its really noticeable while coasting around 21mph. Sounds like a whoop......whoop.....whoop... Sounds like a bad wheel bearing sound is the best way to explain it.
Things that I've done or checked are
new tires
new brakes and rotors all the way around
New carrier bearing, U joints checked
New left and right wheel hub bearings
Parking brake shoes are removed,
rear rotor dust sheilds are not rubbing.

One other note my limited slip rear end has locked into positrac while pulling into the driveway. But unlocked after driving 100 feet. This has happened twice in the last year, but not any time recently.

What else should I look for?

[Scrapper]

a new tire can do this to belts arn't anygood change 1 of the tires to the rear and see if it sounds like it's coming from another place just to see if it's not 1 of the new tires? other would be a wheel bearing i'd think if you checked all other you say you checked. and take the cover of rearend and check out the gears.

[Kitchen363]

Just driving home from work today and the noise it getting worse. Now I can hear the whoop.....whoop....whoop..... at 40 mph. And also have a higher pitch noise last last for about 4 seconds then goes away then comes back. This happened @ 40 mph.

Thinking this thing might have to go to the dearlership. I still would like to check out the rear end oil to see if I find some metal stuck to the magnet.

[j cAT]

Originally Posted by Kitchen363

I've got an noise comming from the rear of my 2002 2wd ext.cab Silverado.

Its really noticeable while coasting around 21mph. Sounds like a whoop......whoop.....whoop... Sounds like a bad wheel bearing sound is the best way to explain it.
Things that I've done or checked are
new tires
new brakes and rotors all the way around
New carrier bearing, U joints checked
New left and right wheel hub bearings
Parking brake shoes are removed,
rear rotor dust sheilds are not rubbing.

One other note my limited slip rear end has locked into positrac while pulling into the driveway. But unlocked after driving 100 feet. This has happened twice in the last year, but not any time recently.

What else should I look for?

you spent alot of cash replaced alot of parts. why didn't you open the rear diff and inspect for wear and damage.

also you have a locking diff. not limited slip.

that means when one rear wheel rotates more than the other these rear axles lock together for a number of rotations then release.


limited slip diff is always locked together by a limited amount due to clutches..not good if you pulling a load..........



with rear wheels off the ground and the diff cover off rotate and check all bearings/U joints..

what gear oil did you use ? rear diff requires 75-90wt synthetic .replace 30-40,ooomi............

[jdmccright]

I didn't see a check of the fluid level and condition. Also, if it was changed recently, it should have had a friction modifier additive added to the oil...limited slip diffs need this, positraction diffs don't. If it was omitted, then there could be damage.

[Kitchen363]

The rear end oil was changed about 18 monthes ago with synthetic oil and I added the limitied slip additive. Guess I'll take the cover off this weekend and check it out.

With the wheels in the air and the cover off, if the bearings are bad will I see or feel some slop. I guess I'll look for metal on the maganet too.

How hard are the bearing to replace? Are they pressed in of can I drive them out with a large socket???

Originally Posted by j cAT

you spent alot of cash replaced alot of parts. why didn't you open the rear diff and inspect for wear and damage.

also you have a locking diff. not limited slip.

that means when one rear wheel rotates more than the other these rear axles lock together for a number of rotations then release.


limited slip diff is always locked together by a limited amount due to clutches..not good if you pulling a load..........



with rear wheels off the ground and the diff cover off rotate and check all bearings/U joints..

what gear oil did you use ? rear diff requires 75-90wt synthetic .replace 30-40,ooomi............

[j cAT]

Originally Posted by Kitchen363

The rear end oil was changed about 18 monthes ago with synthetic oil and I added the limitied slip additive. Guess I'll take the cover off this weekend and check it out.

With the wheels in the air and the cover off, if the bearings are bad will I see or feel some slop. I guess I'll look for metal on the maganet too.

How hard are the bearing to replace? Are they pressed in of can I drive them out with a large socket???

limited slip additive is not for you vehicle. you have a eaton locking diff. you must use 75-90wt synthetic period...............nothing else..

my 96 impala ss has the limited slip diff ........this is very different from the eaton locker !

first see what is wrong ...could be many things ...

my guess is U joints......

[Kitchen363]

Well........ I opened the rear end cover and found nothing out if the ordinary.
Added some new fluid and still have the noise. But not as loud?? But have another noise at 40 mph after I let off the gas pedal. I whinning sound??

I guess my next step is to just drive it till the wheels fall off. I'm just going to watch for leaking seals around my bearings on the drive train.

I just can't see myself going to the dealership and spending a lot of money on it.

Any other thoughts on what it could be???

[j cAT]

Originally Posted by Kitchen363

Well........ I opened the rear end cover and found nothing out if the ordinary.
Added some new fluid and still have the noise. But not as loud?? But have another noise at 40 mph after I let off the gas pedal. I whinning sound??

I guess my next step is to just drive it till the wheels fall off. I'm just going to watch for leaking seals around my bearings on the drive train.

I just can't see myself going to the dealership and spending a lot of money on it.

Any other thoughts on what it could be???

when you opened the diff cover did you have both wheels off the ground to inspect the diff gears/teeth/diff bearing/U joints/wheel bearings for wear ? what fluid have you been using ?

did the diff teeth have a good wear pattern ? this is important...could be needing shims to correct for excessive wear !

If you have used the wrong fluid with the eaton locker diff I would expect a noisy diff.. If you use the correct fluid and replace every 20-30,ooomi It could last a few more noisy yrs before it fails totally..

[Kitchen363]

Originally Posted by j cAT

when you opened the diff cover did you have both wheels off the ground to inspect the diff gears/teeth/diff bearing/U joints/wheel bearings for wear ? what fluid have you been using ?

did the diff teeth have a good wear pattern ? this is important...could be needing shims to correct for excessive wear !

If you have used the wrong fluid with the eaton locker diff I would expect a noisy diff.. If you use the correct fluid and replace every 20-30,ooomi It could last a few more noisy yrs before it fails totally..

Had both wheels off the ground. everything seemed good, smooth and tight. About 20,000 miles ago I replaced the rear end fluid with Mobile 1 synthenic 75w-90 and added lmited slip additive (which now I'm learning was wrong) because I have a locking diff.

Now I have just Mobile 1 Synthenic 75w-90 gear oil.

One more bit of info. With the wheels off the ground I removed the wheels and brakes and rotors. I could push in and out on the axel. I seemed to move slightly in and out. Less than a 1/16" of an inch.

Hopefully it can last a feew more years

[jdmccright]

Sorry if I made things confusing...I was going off you stating you had a "limited slip" diff. Yes, Eaton lockers (G80 RPO code) don't use the friction modifier.

You could jack up the rear, chock the front tires, and have a friend put the truck in gear while you listen underneath:

center support bearing (extended/crew cab)
u-joints
pinion shaft bearings
differential
axle bearings (already replaced according to you)

Use a long piece of wood or metal rod as a stethoscope to listen to each component.

[j cAT]

Originally Posted by Kitchen363

Had both wheels off the ground. everything seemed good, smooth and tight. About 20,000 miles ago I replaced the rear end fluid with Mobile 1 synthenic 75w-90 and added lmited slip additive (which now I'm learning was wrong) because I have a locking diff.

Now I have just Mobile 1 Synthenic 75w-90 gear oil.

One more bit of info. With the wheels off the ground I removed the wheels and brakes and rotors. I could push in and out on the axel. I seemed to move slightly in and out. Less than a 1/16" of an inch.

Hopefully it can last a feew more years

the axle end play of about 1/16 inch is good and normal...


when rotating the axle and wheels it should feel smooth , and held secure by the bearings ....also looking at the gear teeth when rotating for wear pattern to be in the middle area of the teeth...

I use mineral spirits/low odor paint thinner with a cloth and wipe down the diff box.........

at about 40mph a low level hum is normal...as the wear increases with age these diff noises will get more noticable..

these diff's when NEW require a special breakin period of several hundred miles...the gear teeth are conditioned/hardened at this period...If the vehicle was driven too hard for too many miles this damages the metal causing wear or even metal to be brittle and crack...

replacement of the oil after 1500miles when new is recommended..this is because the diff can get toooo hot ...fluid must be replaced as a precaution....

after this mileage [1500 mile] the diff is said to be ready for work...

I found this all out only a few years ago ! thanks GM for failing to inform me of this !

[ukrkoz]

whoop-whoop-whoop is not bearing noise. bearings go bad with beetles crunch, not whoop. besides, it will be continuous noise, not intermittent.

any whoop-whoop i had to deal with so far was due to bad tires. hump in the tire; ripped belt inside; tires nowadays ain't worth a flip, radial pulls common issue, belts rip; if flattire (tireflat?) was ever used, it gumms up inside, and sometimes peels off the inner tire wall and start bouncing inside.

LOOSE LUG NUT or loose stud. anything that will allow wheel to wobble on the hub.

loose hub bearing.

take your wheels off and look at the inner side wall. and signs of rub anywhere?

to eliminate tires as culprit, put front tires onto the rear end. or, if you know exact side whoop is coming from, just swap that side tires.

[j cAT]

Originally Posted by ukrkoz

whoop-whoop-whoop is not bearing noise. bearings go bad with beetles crunch, not whoop. besides, it will be continuous noise, not intermittent.

any whoop-whoop i had to deal with so far was due to bad tires. hump in the tire; ripped belt inside; tires nowadays ain't worth a flip, radial pulls common issue, belts rip; if flattire (tireflat?) was ever used, it gumms up inside, and sometimes peels off the inner tire wall and start bouncing inside.

LOOSE LUG NUT or loose stud. anything that will allow wheel to wobble on the hub.

loose hub bearing.

take your wheels off and look at the inner side wall. and signs of rub anywhere?

to eliminate tires as culprit, put front tires onto the rear end. or, if you know exact side whoop is coming from, just swap that side tires.

where you been ?

he bought new tires same woop / whine noises !

[Kitchen363]

The sound kind of became a little bit more quite for a few days. Now its back to being fairly loud. Most noticeable at 20mph and 40 mph with light load on and motor or even coasting.
Sounds like it is coming from the center of the truck under my seat?? Could it be the transmission output bearing?? I just can't see that going bad. Plus there is no leaking seal on the transmission???