Recently I had to replace my Rear Differential Cover on my '99 Blazer due to a pin hole sized leak in it. While doing so I noticed that a tooth had sheered off somewhere inside. After doing a little inspecting I found it had come from the Pinion Gear that comes off the drive shaft into the differential. I'm not sure how long its been like this (could be since i bought it 40k miles ago). Today on my way to work I didn't have the music blasting and could hear a slight grinding coming from what seems like the *** end. When I would let off the gas pedal to decelarate the noise got 10x as loud and I could feel silight vibration (sounded like a "Jake Brake" on a semi). I really am hoping that I don't have to have my rear diff rebuilt. Any ideas of something else it could be before I take the plunge into having that done?

 

Dang I just replaced the outer axle bearings & seals and also the front pinion seal along with both u-joints. I just took it for a test drive and I hear the same damn howling noise. All of my teeth were good though. I am so pissed right now.

 

You have no choice except to replace the ring & pinion gears. They should be matched. (ie both new or used) If you don't you run the risk of ruining the whole rear end.
A howl is as a rule a wrong clearance between the ring & pinion gears. But since you just did the wheel bearings you may have a problem there. If you didn't have the noise before.

 

I did another test drive and it only makes the howl when I let off of the accelerator at all speeds. When its under load, its happy. I only changed out the outer bearings by the wheels; I didn't touch anything inside.

Is it tough to replace all of the bearings inside? I might as well search for a zexel while I'm at it too.

I bet I screwed up the pinion spacing when I tightened the yoke nut back on. I marked it but I probably did something wrong. Dammit.

 

BINGO!!!

even my trans/diff expert (who has 25+ years experience) doesn't like removing a pinion nut from a worked in set-up.

sounds like you need to check you back-lash ASAP!

 

How hard is it to adjust backlash? Does everything have to come out? It didn't have any measurable pre-load before I took off the yoke. This rear end is on its way out. Its had a faint whine since I bought in (has 186,000 miles on it now).

Can i pull out the Eaton assembly and then just pull the pinion out to at least change out those bearings?

 

Your options are to get it fixed now when it is scheduled or to get it fixed after a tow in the worst possible location and time. You can get a shop to put in a used unit from a local wreck yard, they will come with a warranty, sometimes a unit that sat needs a new set of bearings and seals. About a $700 job.

 

Check around for prices on a complete rear-end from a U-pull and pay or local yard, just make sure you get the right gear ratio. I was able to replace the whole rearend in my wifes Cherokee for just at $100. The worst part of the job was rebleeding the brakes (had my ten year old help pump them as I bleed) then adjusting the shoes.
I'd leave setting up a ring and pinion to someone that has successfully done it a few times.
I've had good luck switching carriers, I just made sure that whatever shims I took out, went back in the same. I've managed three posi carrier swaps this way and never got any whine or play. I had a shop do a complete rebuild on a rearend for my old GMC once, I was changing gears so I past on doing it myself for lack of experience. I got the friend of a friend set up for $200, that was a lucky price break I'm sure.
If you do plan on having it gone through at least see if you can find a hook-up that will let you watch, that way you can get a free lesson..
Good luck!!

 

Oh yeah, just wanted to make a note. We live in a republic not a democracy. If we lived in a democracy and left it up to those that allow themselves to fall victim to the manufactured media this country would have fallen long ago. The sad thing is the democratic idealism is taking over yet moving more and more to socialism each day.
It's time to take back our republic and kick the non-working lazy saps off their couches. I didn't get anything for free so don't expect me to give it away to a nobody.
Didn't mean to get political, just wanted to point out it's a republic not a democracy.

 

TJ knew what was going on; if you give too much to the lazy, it'll all collapse.

I did a cursory eBay search and found a local vendor that has at least 10 3.42 G80's in stock. Some allegedly with only 7k miles on them for $300 to $450. I'm going to tweak this a little more before I buy a used one.

The noise is only when I let off of the accelerator. I just remembered something interesting - when I put the yoke back on and tightend it exactly to the original location, it seems that the yoke is not as close to the diff as it was before. Did the yoke move forward somehow? Is this possible? How hard is it to just replace the crush sleeve?