99 z71 ( New Style )
Changed passenger axle seal in Oct. 2003.
Changed front pinion seal, front transfer case output seal, front
u-joints Dec. 2003.
4WD Howls in AWD and 4Hi under load.
Axle seal leaking again.
TC output seal small leak again.
I just had the front differential rebuilt. The guy that rebuilt it
found the races of the bearings ( I am assuming side bearings ) to be
pitted. He also found a small piece of metal about the 1/4 the size
of a penny that he couldn't find out where it came from.
Well, I installed the differential today and the howling is as bad as
I have seen a few others have had howling front ends in 4wd. I plan
on taking it back to the guy who rebuilt it on Monday to see what he
Have I wasted $500 on a unnecessary rebuild?
Does anyone know how to quit down these front axles?
My truck didn't make the noise the first 50,000 miles. My wife has a
2002 tahoe and it doesn't make the noise. There has to be something
"Erik" wrote> 4WD Howls in AWD and 4Hi under load.
$500 dollars for the rebuild? The guy can't have put much
more then the side and pinions bearings in. Is this a pro
doing this work? How do you (and he) know that the
gear set isn't toast? The problem with gear sets is that
if you run any gear set for any extended length of time
with worn bearings, you inevitably wear the gear set
in such a way that it will never be quiet again...no matter
what you do. Most of these front diffs that I'm rebuilding
are getting new gear sets, as the amount of "play" that
the gear set has been running at does damage to the
gear set, and even if you set it back up perfectly, it
will still be noisy.
Proper pinion and side bearing preload is fairly
critical on these front diffs. Hopefully he is using
a deflection inch/lb torque wrench in order to
get the correct pinion bearing preload and then
the correct pinion/side bearing combined preload.
Actually, it was $450, $200 parts, $150 Labor + Tax.
It is a local transmission shop. He was one of 2 guys in town that
would do it other than the dealer.
I have no clue when it comes to rebuilding diffs. Thats why I took it
to the shop. When he quoted the rebuild he did say that I would be
getting into a lot more money if the gear set needed replaced. After
he got it apart, I asked him if the gear was ok and he said it was.
quiet again...no matter what you do.</i>
If this is the case, is the noise just a nuisance or will it cause
Are you finding that races of the side bearing are pitted like the guy
Hopefully, they decide to take it apart again and make it right. They
did give me a 30 day warranty. I guess if tries to say that this is
normal for these trucks then I'm probably screwed.
Thanks a lot for your replies
No doubt, there are very few mechanics anymore
that know how to, or want to tackle a differential
overhaul. I'm very fortunate that when I was an
apprentice, I got handed tons of diff work (it's considered
the shit work) and as a result got a good handle on
how to overhaul a diff properly.
Ok.....he may be right, he may be wrong. That's the other thing
about a gear set, it's really almost impossible to look at the gear
set and tell if it will be noisy or not when you set it back up. If
there has been any kind of play in the bearings, I usually estimate
the gear set as part of the repair, and if the customer doesn't want
to go for that, it either doesn't get done by me, or I will put bearings
in only with major disclaimers about how the gear set could still
> >>you inevitably wear the gear set in such a way that it will never be
For the most, it will simply be a nuisance. The important thing
is that the bearings are in good shape and properly adjusted.
But most customers we deal with expect the diff to be perfect
when they are handed the vehicle. And of course, much of the
diff work we do is warranty, in those cases, we put in whatever
parts we deem necessary to make sure that gear set does not
> Are you finding that races of the side bearing are pitted like the guy
Yes, it's always the side bearings that go. At least, everyone that
I've seen apart in our shop has been the side bearings.
> Hopefully, they decide to take it apart again and make it right. They
Hopefully you can get it resolved. I don't know what the tech
said to you about the diff, so I don't want to slam him as I only
have your side of the story. You might ask him if he checked
the pattern of the gear set when he had it all back together?
He'll probably say yes, but you never know.
I am not slamming him either. The shop seems to be treating me fair.
I knew I was taking a bit of chance without taking it to the dealer.
However, I'm get the impression that the dealer is big bucks. I also
looked into getting a used one but after seeing you state that you
have seen numerous bad diffs, I was worried about getting another bad
Well, I took the truck to the shop today. They put it up the rack and
no noise in the front end in 4wd. When he did this before the
rebuild, it was making quite a bit of noise. Hopefully, that is
progress. I told him it only makes the noise under load. So, we took
it for a drive and sure enough it howls in 4wd when you give it gas.
He said something about a crush bearing and that he wanted to put a
torque wrench on the pinion. I would guess that means he is going to
check the pre-load. I left it with him, but he didn't get a chance to
look at it. He said that he will first thing tomorrow.
Well, He said basically the same thing you did. Maybe he's reading
this thread :). He sad that the pattern of the gear set may have
change because of the bearings be shot. He said sometimes after you
drive it for a while that it may quite down. So, he told me to drive
it for a couple of weeks and if doesn't quite down then bring it back.
He also said that he tightened up the pinion nut a bit and that
quited it down some. I didn't notice any difference.
It would seem to me that the bearing being shot wore the gear set and
that the howl I was hearing ( or at least some of it ) was due to the
gear set from the start. I am skeptical that driving it for a couple
of weeks will make a difference.
I imagine in 2 weeks I am going to be making a decision on the gear
set. Thats going to be a tough one. Especially, if I have to pull
the diff again and pay for the labor to have taken apart again.
This morning I crawled under my truck to change the output seal on of
TC. I have been putting it off until I'm certain the diff is OK. The
leak is very small.
Well, while I was under there I checked the front diff. The pinion
seal is leaking. I am definitely going to be taking the truck back to
the shop that did the rebuild now so I may as well let them change the
tc seal since they are going to be pulling the drive shaft anyways.
Also, I am not sure if my diff has quited down any or if I have got
used to the howl. It doens't seem to make as much noise as when I
first picked it up. Though, it still howls when under load.
Is it more likely the pinion seal is leaking due to improper preload
or because of the gear set pattern? If its the preload, is it likely
I trashed the side bearings again?
If the seal is leaking, you have a number of reasons why
it's leaking. It was improperly installed, perhaps damaging
the outside circumference of the seal, the surface that the
seal goes into could have been nicked by a careless tech
removing the original seal, the preload on the bearings may
not be sufficient, allowing the pinion shaft to flex under load,
or the surface of the yoke that the seal rides on might be
pitted or grooved.
Improper preload of the pinion bearings won't have any
direct effect on the side bearings.
I have a `97 Z71 w/73,000 on it.
I bought it in `99 w/24,000.
It has always howled in 4 wheel.
Took it to my buddy at the shop.He changed fluid and checked everything.
Nothing wrong. It`s just the way it is.
I beat the hell out of mine,so there can`t be anything wrong.
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