Hello everyone,

After tiring myself out over the month looking at all the different threads about rear end noise, and after having a shop look at it I have decided to make my own thread in hopes someone can offer some solid insight!

It's very cold here in Canada, Typically -30 the last few weeks, which is when the noise is most prominent. The noise seems to be louder some days, and softer other days (usually the noise is somewhat quiet during warm weather). It is like a groaning rumble or friction rubbing sound, I cant explain it it properly using dumb acronyms but maybe "Whooooorm Wooorrum Wooorum" at slower speeds, and typically being a constant rear end groan/grind sound at about 40-60KMPH, at 80 very noisy - and around 100 it kind of disappears altogether with the highway speed or highway noise, I'm not certain.

It began about 4 months ago when winter started, I really noticed it one day out of the blue, After I was stuck in a parking spot that sloped downwards - The rear end was stuck in ice, and 4x4 wasnt working at the time so I had to run the tires out a bit on the ice to get out, It was since then that I noticed the noise most.

I took it to a shop, they said they could kind of hear it but it wasnt noisy enough for them yet, To be able to diagnose it and they said to bring it back when it was worse. He said it sounded like it "could be the rear end, bearings... not wheel bearings though" I am not sure what bearings he referenced at the time

Some things to note:

Truck is 1998 SLS Jimmy variant, with 340,000KM on it. Has had a tranny rebuild.
-new ujoints on it
-tires are quite worn out, with barely 1 tredmark left.
-Rear Disk Breaks
-I have recently changed the diff fluid with synthetic high end after changing the blackened neglected fluid of the prior owners
-Breaks sometimes stick in cold weather when I am accelerating from a stop light, Kind of a delayed sticky release after I lift my foot from the pedal (Only felt from rear end)
-Ebreak Release handle is long gone, Only way to release break is by pulling on cable from under the dash, Possibly the ebreak is partially stuck?

When I tugged on the ebreak cable as the truck was hoisted up, I noted that it worked properly, not sticking, I tugged it and released it a bunch from the left side - Afterwards, it seemed like the noise was VASTLY diminished compared to what I was used to hearing, Until the cold weather started to kick in again and after driving on it for awhile (8 days).


What could it be?

Here is what I think:

It could be the Ebreak partially sticking, the breaks not fully releasing for some reason, the axle, or maybe (hopefully) not the main rear end components.

Please help me, I'm desperate to have this fixed and I dont want to spend 90$ an hour labor on troubleshooting the wrong thing!

 

Grab a hold of the yoke at the front of the rear diff and feel for play. If you have play here, then the pinion bearings are going. This type of wear will commonly cause the pinion seal to leak.

You can check the outer wheel bearings by jacking the rear end up and properly supporting it. Then lift the wheel, feeling for play.

You should be able to feel for roughness in the e-brake (internal drum brake on the inside of the rear brake rotor) with the rear end in the air.

How did the gear set look when you serviced the rear diff?

 

As far as as know, The gears were okay. There wasnt anything that raised any concern at the time. I am not leaving it out of the realm of possibility, But

Ironically the Pinion Seal is leaking! I noticed this when I had it in the air, I was told I needed a new pinion seal, Perhaps it is the Pinion Bearings that are going afterall - Since it is leaking as you say. (Could be a coincidence, Might be a probability)

I'll check the yoke for play as soon as I can, as well as roughness in the ebreak - I don't think its wheel bearings cause there isnt really any play at all.




Assuming it is the pinion bearings, is this a tough or expensive job?
Any possibility its something else, If not, And it is likely the pinion bearings, How long will these go for in a worn state such as I have described? Will fixing it later have complications, or safety issues VS having it fixed now?

I really appreciate the informative reply, Thank you

 

If you have to replace the pinion bearings, then you will be rebuilding the whole diff. I would have a shop do this and have them replace all bearings/seals. They have to remove the axles to pull the diff center section to get to the pinion so it all is coming apart anyhow.

 

Understood,

Sounds like an expensive (1500$ Range) job.
_________________

How long can I expect it to last in its presently worn out state?

I am strapped for cash, Bills; Economy, cost of living are eating up my income like swiss cheese

I did have a summer ride lined up but now I am not so sure.


Should I be considering a used rear end VS Rebuilding? Or is the difference in work minimal, we all know labor exceeds the price of parts by a vast margin.

 

If a rebuild of the rear axle is needed, then replacement of the whole axle for a used one would be much more economical.

 

How would I determine of a rear axle rebuild is needed? After a teardown of the rear end and internal inspection by a mechanic?

In which case, I would simply purchase a used rear end, including diff, axle and other related components?

If you know - How many hours of labour might this be?

 

Removing the cover and inspecting the internals is all that is required to determine if the rear end is bad. Heck, if it is the pinion bearings, you can determine this without even removing the diff cover. Just grab the pinion and if you feel play up/down or in/out, then it is shot.

And how much labor would what be? Inspecting the rear end, rebuilding it, or replacing it with a junkyard axle?

 

Well,
Took it all apart.

Found the rear breaks needed new calipers, pads and rotor resurfacing.
After having the breaks apart, Noticed the Axle seals were leaking.
Ordered new axle seals.
Took the old ones off, and the bearings, Noticed there was a 1mm Line of wear where the bearings spin on the axle, the drivers side was worse then the passenger side.

-Ordered 2 Used rear axles that were in good shape
When axles were off, Took the diff apart.
Noticed the smaller gears were pitted, The larger one was fine though.
Noticed the pinion bearing surface had an area of about an inch that had pitted itself
-Ordered nest kit
-Ordered bearing kit

new pinion, pinion bearing and all seals.

Put in a fuel filter while it was apart

the damn thing drives like its brand new now..
yeesh.

Thank you


Wonder how much longer this thing is going to last before another serious repair,
I hear 340,000KM is alot for a 98 Blazer, perhaps I should consider a timing chain incase it breaks someday?

 

Wow. That was a lot of work that needed to be done! Probably should have gotten an entire used rear axle.

Glad you got it all fixed up!! You did not happen to take any pictures during the whole process did you?