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Rear end whine?

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5speedz34

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Discussion starter · #1 ·
This is my first post so please bear with me. I have a '01 Sonoma Crew Cab(4x4, 4.3/4L60E, 3.73 gears/limited slip, 90k).

Since about last September I've been getting a whining sound. It starts at about 15-25 mph, and gets louder with speed. I can only hear it when my foot is on the gas, coasting I hear nothing.

The tires on the truck need to be replaced and the truck needs an alignment. I think it might be the rear end, but would it whine this long before something serious happened?

I pulled the plug today, the fluid seemed sorta low, but it was a light brown, and was very gritty and dirty. I plan on changing the fluid, but I want some insight into if this is my problem.

I want to change the front and rear diffs. Has anyone heard of flushing a differential? And what type of fluid do I need (I think the rear takes Autotrac II or something, maybe since its LSD?)

Thanks alot guys, I love the forum!

Tony
 
#2 ·
ok well let's start with the basics. are the rear tires cupped? if they are or your not sure try rotateing them to the front. then see if the noise is gone or moved to the front. if it moved or gone then all you need is tires. if the noise is still in the rear then you may need to look into the rear a little more.
 
Discussion starter · #3 ·
offroadblazer said:
ok well let's start with the basics. are the rear tires cupped? if they are or your not sure try rotateing them to the front. then see if the noise is gone or moved to the front. if it moved or gone then all you need is tires. if the noise is still in the rear then you may need to look into the rear a little more.
Click to expand...
Ok, I don't think the tires are cupped but they are in pretty shitty shape. I'm hoping to have new tires in a week or two.

In the mean time, I want to change my front and rear differential fluids. Have you ever heard of flushing the differentials? And is it as simple as just taking the covers off, letting them drain and refilling them?
 
#4 ·
Changing the fluid is very easy. Drain the old fluid and fill up with new 80w-90 gear oil.
As far as the noise, the only sure way to eliminate the possibility of ring and pinion not meshing correctly (source of the whine) is to check the gear contact pattern using marking compound and check the pinion preload with a dial type torque wrench. If the old oil is was low and "dirty", chances are you may have overheated the gears and bearings.

If you aren't familiar with changing your diff oil, chances are you won't know how to do this and will probably need to have a qualified tech look at it. The actual repairs are a bit involved and can get expensive.
 
Discussion starter · #5 ·
ppap said:
Changing the fluid is very easy. Drain the old fluid and fill up with new 80w-90 gear oil.
As far as the noise, the only sure way to eliminate the possibility of ring and pinion not meshing correctly (source of the whine) is to check the gear contact pattern using marking compound and check the pinion preload with a dial type torque wrench. If the old oil is was low and "dirty", chances are you may have overheated the gears and bearings.

If you aren't familiar with changing your diff oil, chances are you won't know how to do this and will probably need to have a qualified tech look at it. The actual repairs are a bit involved and can get expensive.
Click to expand...
Changing the fluid should be no problem for me, I'm pretty experienced when it comes to cars. I'm just more familar with FWD.
 
#6 ·
Hey tony
I own a 02 crewcab s10 with 136k and it has a rearend Whine too, it was bought at a gm Dealership. it alwas had the whine, Im gona pull my diff and take a look.
My friend bought a fullsize with a rearend whine as well it might be just a Chevy trait... or it could be overheated bearings...
goodluck friend
 
#7 ·
It sounds like to me that it may be a pinion bearing whining, If it is not the tires. Noise only under load.

Change the fluid and fill it up, replace your tires annd see what happens. If the noise is only heardon accell and not decell than you have a bearing problem.
 
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#8 ·
z34 has a bearing problem. common.
 
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