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Discussion Starter #1
The rear end on my 99 (old body style) sierra 2500 2wd has been making noise ever since I've owned it But now its getting worse. It makes a howling noise that changes pitch the faster I go. I changed the oil in the diff a few months ago and it didn't seem to make a difference. I'm pretty sure It's a 14 bolt back there because it's massive. A friend told me that just because the diff has fluid doesn't mean that the axle tubes do. Do you think it's possible that the axle tubes are dry and the noise is metal on metal?
 

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It is very possible that it is the axle that is grinding not your diff. I had a 98 s-10 that was making a whining noise that kept getting worse, then it started grinding. Thought it was the diff took the whole rear end off to take a good look diff was fine but the sleave bearings were going out in the axle replaced the whole rear end, pretty easy fix if you can find a good part at a junk yard.
 

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The 14 bolt rear is pretty much bulletproof. You must have abused the crap out of it. Anyway, its not that hard:

OPen up the diff cover and check for metal shards in the pumpkin. Flakes/shavings are ok, but not chunks. after that, pull out the axel shafts and replace all bearings -- not expensive, but time consuming.

If there are chunks of metal in the diff housing, pull out the carrier and inspect the spider gears. If they are shot, I'd just go ahead and buy a new carrier (not that expensive +/-$100

Check your ring gear for any uneven wear by the pinion.
 

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Any chance it has a magnetic drain plug?They are pretty useful for diffs since everything in there is steel-no aluminum.
On the very small bright side, be happy it isn't a Titan.They are nice trucks,great motor trans, but they have been eating rear ends at very low miles,and as recently as 2006 they hadn't solved the problem.Nissan was good about replacing undwer warranty, but once you were out of the warranty-50,000 or 60,000 miles you were on your own to the tune of $3000(they replaced the entire rear end-not just the diff or gears in the diff).The diff is a modified Dana 44-should have been enough-but there were/are QC problems(something about the powdered metal gears not being heat treated properly is the best guess-done offshore somewhere not in the USA is the story-typical cheapout)
Luck,
Charlie)
 

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Discussion Starter #5
haha I wasn't the one doing the beating on the 14 bolt It's been whining since I got it, just getting progressively worse. The truck has 197,000 on it so that could have something to do with it.
 

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When was the last time you changed the fluid? Also, look at the back of the diff housing, where the pinion is, and see if its leaking.
 

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Discussion Starter #7
A month or two ago. Fluid levels are good and there's no shavings or chunks in fluid.
 

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Is it a locking diff. If so and you don't use the proper oil it will howl.
 

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Discussion Starter #9
Nope its and open diff. It's gotten me stuck many times.
 

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first thing i would check is the axle bearings
 
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