Hello everyone. I drive a 1999 Blazer LS, 4x4. About 150,000 miles on it now.

Over the years I have done a lot of maintenance items on it. I think it is VERY well cared for.

Recently started hearing a noise coming from the rear end housing. It sounds like when you would put a baseball card in the spokes of your bicycle when you were a kid.

The noise is louder under acceleration and the frequency of it picks up the faster you go (Like a baseball card in the spokes of a bicycle).

I already replaced the U-joints on the driveshaft and bought new U-bolts. The problem still exists. I jacked up the back end, started it up and put it in gear to turn the rear wheels.... definitely coming from the rear end housing. Not sure if it's the gear or not.

Am I looking at outer axle bearings or is this most likely a spider gear issue?

I realize there are several threads discussing rear end issues, but I am curious if the symptoms/noises other people experienced are similar to what I am hearing.

Thanks in advance for your help!

 

Hello Intimidator79,

I don't have the same noise you have. Mine at the moment is a very loud
whining sound. I think the best thing to do would be to put it on
jack stands, take off the rear differential cover and have somebody move the
wheels by hand to see what gears in the rear end are making the noise.
My guess is that a tooth/teeth have come off the Ring and Pinion or Spider Gears.
The only way to know for sure would be to open it up. I have attached a pdf to
show you how much is going on back there. Not sure if you have disc or drum
rear brakes. Not sure if you have the 7.5 or 8.5 gear ratio. The drawing is for
a rear end with drum brakes. Hope this helps. Not sure if you were going to
try and tackle this yourself. Numbers 7, 22 and 23 would be your Ring and Pinion and spider gears.

Mark K

 

Thank you for the diagram.

This situation has really irritated me. Decided last night that I was either going to be rebuilding/fixing the issue with the rear gear or I was heading to the junk yard to find a totally different complete USED rear end to put under it.

Tore the entire rear end apart and found about 4 teeth either missing or severely damaged on the pinion.

Noticed that the carrier moved back and forth (left to right) as if the bearings were bad. Actually.... one of them just fell apart when I pulled the carrier out.

It was full of fluid and other than the pinion teeth sitting at the bottom of the housing, the fluid didn't look too bad.

Very puzzled at how this could have happened.

I've been around race cars my entire life and have built my fair share of Ford 9" gears. I've never had one of those fail, so I was at a loss for even trying to diagnose a gear failure.

I'm hoping I can tackle this project myself.

I am in great need of some diagrams for doing this. Torque specs, backlash, pinion depth, etc.....
Pretty sure the ring gear is stamped 7 5/8". Hard to read. Does that seem right?

Any help is appreciated.

 

Hello Intimidator79,

Not sure about all the mathematical specs, I am sure somebody with more
knowledge will pitch in. 7.625-RPO Code GU6 sounds correct.

I have raised this question before about the quality of the Ring and Pinion Gears.

I have close to 200,000 miles on the original stock rear end. I figure if I were to
buy new innards needed to fix it up properly I might be spending about $700 in
replacement parts. Plus I cannot do the work. I am only book smart. I figure about
$1100 in parts and labor. I think the costs make most people run to the salvage
yard and find a rear end that fits/replace. It is probably more cost effective but who
knows the true history of what you are getting.

Mark K

 

I had a similar issue on my '96. I had a vibration coming from the rear axle. No whining or loud noises, though.

Took it to a 4 wheel shop because I wanted them to install a Detroit TrueTrac LSD. My Blazer has 170K on it. In the end, it cost me just shy of $1400. About $900 for the TrueTrac plus labor, but I ended up needing a lot of extra parts replaced mainly due to age.

The u-joint was frozen in one axis, replaced. New pinion seal, leaking. New pinion bearing, new axle bearings, etc etc. I could've left all these in place and not replaced everything, but somewhere down the road, when I need the truck the most (I live in MN), something would break and cost me even more money to fix.

It's good that you caught it now. The best part is that you don't need a whole new axle, just the guts. I would highly recommend getting an LSD (the TrueTrac is very streetable and I love it) while you're at it.

 

Update:

I spent most of yesterday checking prices on what I need to rebuild this thing. Advance Auto Parts had the best prices on everything.

Ring and Pinion, 3.42, 7 5/8": $197.99
Bearing (Rebuild) Kit: $109.99 (includes all bearings, pinion seal, nut, gaskets, marking compound etc...)
New Spider Gears/kit: $97.99
Outer Axle Bearings: $27.99 each
Outer Axle Seals: $3.99 each
Shim kit for Carrier: $5.99


Got a friend who owns a pretty sizable/reputable junk yard around where I live. Was telling him about my situation and having him price out an entire rear end unit for price comparison. He had several options and they were all in the $250 to $400 range depending on mileage. My issue with replacing the entire rear end is that I don't know if what I'm getting is all that much better than what I have. Don't want to be going through this again in a year.

Then he threw this out at me:

He has an entire posi carrier that came out of an S10. Ring, Pinion (carrier assembled). Very low milage (23,000). Same ratio, size, etc that I need.

Being that I have a limited slip differential now, this would be an upgrade in performance. He wants $150 for it. I'm thinking of doing it and buying the new bearing kit and everything else for a decent rebuild. This will save me $50 on the ring and pinion and the entire cost of the new spider gears.

Anyone else have the posi differential in their blazer/S10? I live in a place where it snows a lot. I'm guessing a posi won't be a bad thing.

 

You thinks he's talking about the Rating unit?

Just youtube Eaton G80 Locker and get ready to be amazed.

I myself, went all winter in the snow in two-wheel-drive. Except for pulling a couple of much bigger vehicles out and up hills!

 

Yes it's a G80 locker which, until recently I had no idea what it was. Apparently the Eaton assembly is exclusive to GM. Very simple design and apparently very effective.

I'm excited to get it installed and try it out this winter!

Right now I'm waiting on the installation kit. Since I determined that my problems resulted from a bearing failure, I want to install new bearings on the G80 unit just to be sure. Not that much of an expense.