[GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test

[Bruce Hislop]

So I went to NAPA thos morning to pick up the SKF-21771 rear bearing seals. I brought along a 1/4 hex bit to test the seal which actually measures
0.247". It fails the test as your can see in these photos.

http://www.gmcmhphotos.com/photos/g7044-skf-21771-rear-seal-fails-test.html

Any ideas?

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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[A.]

RF_Burns wrote on Mon, 29 May 2017 11:52
> So I went to NAPA this morning to pick up the SKF-21771 rear bearing seals. I brought along a 1/4 hex bit to test the seal which actually

> measures 0.247". It fails the test as your can see in these photos.
>
> http://www.gmcmhphotos.com/photos/g7044-skf-21771-rear-seal-fails-test.html
>
> Any ideas?

Have them open every box in the store. Maybe one of them is right.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Every day I become more convinced that I am the only person left on the planet that recognizes nonsense for what it is."

[Bruce Hislop]

I checked 3 of the 4. They were a special order in from the warehouse so there was only the 4 I ordered.

[Pete Smith]

What exactly are you testing?

Pete
--
Cary, NC

No Coach yet but likely center kitchen, dry side bath Royale, 78, 403, hopefully with good original white Imron paint.

[Bruce Hislop]

Pete,
Its the distance from the inner face of the metal ring of the seal, to the seal itself. It should be 0.26", below are some photos.

http://www.gmcmhphotos.com/photos/rear-axle-seals-skf21771/p36362-inside-measure.html

http://www.gmcmhphotos.com/photos/rear-axle-seals-skf21771/p36356-says-made-in-the-usa.html

http://www.gmcmhphotos.com/photos/rear-axle-seals-skf21771/p36367-stralian-test-must-slide-under-rubber-lip-rob.html

http://www.gmcmhphotos.com/photos/rear-axle-seals-skf21771/p36372-new-bad-timken-rear-wheel-bearing-seal.html

Apparently seals are being made in which the rubber of the seal is too close to the inner bearing and damages it... letting the grease out.

[Ken Henderson]

Looking through my parts this morning I found 6 of the 21771 seals.
They're all OLD stock -- no less than 10 years old since I've had them in
my storage for that long.

All of the 6 are NAPA-labeled. 4 are relabled Chicago Rawhide; their outer
circumferences are Green. The other two are have only NAPA labeling; their
outer circumferences are Black.

Using a 1/4" screwdriver bit as the clearance gauge, I tested each of the 6
on a flat Formica surface. Here are the results:

Green #1 -- Rubber barely touched the gauge
Green #2 -- Rubber very slightly deformed by the gauge
Green #3 & #4 -- Rubber noticeable deformed by the gauge, WAG 0.003"
Black #1 & #2 -- Rubber very obviously deformed, WAG 0.010"

All of this has piqued my interest, CRS having taken care of most of my
memories from when this topic was originally broached some years ago.
Aside from the contention that the out-of-tolerance seals will allow the
seal to touch the bearing, I don't recall the details of the problem. I DO
recall, however, that somewhere (which I can't locate in any manual now)
there was a requirement that the seal be seated proud of the rear of the
hub. In fact, I still have an un-machined aluminum "seal seater" which
Duane Simmons had Ragusa cast. We were going to use those to make a
special tool for properly seating seals. The aluminum proved difficult to
machine, so we gave up that idea. I did, IIRC, make one from steel which
worked well. BUT, I can remember neither its dimensions nor its location.
:-( Could it be that the problems with at least some of the
out-of-tolerance seals are really caused by incorrect installation? Does
anyone know where the official instructions are for R&R of rear wheel
bearings and seals?

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com

On Mon, May 29, 2017 at 12:52 PM, Bruce Hislop <br...@perthcomm.com> wrote:

> So I went to NAPA thos morning to pick up the SKF-21771 rear bearing
> seals. I brought along a 1/4 hex bit to test the seal which actually
> measures
> 0.247". It fails the test as your can see in these photos.
>
> http://www.gmcmhphotos.com/photos/g7044-skf-21771-rear-
> seal-fails-test.html
>
> Any ideas?
>

[James Hupy]

Ken, you are absolutely correct. Do not seat the seal below the outer part
of the hub casting. Leave it a bit "proud" meaning sticking out a bit for
insurance purposes. Jwid.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

[ree.eric]

Just checked the 4 old stock Chicago Rawhide 21771 seals I purchased on an online auto parts store and they failed the 1/4 test by about .014. Hard to
measure, had to use the plunger end of the caliper and try to keep it vertical, got about .236. Although I saw in the photos someone had used the
inside measuring side of the caliper but the large jaw interferes with the other side of the seal tipping the jaws slightly making the measure appear
to be .25 but the flat surface test with on exact 1/4 screwdriver bit fails. I assume the 1/4 requirement is exact and .236 will not do?
--
Eric & Ree '74 ex-Sequoia + '75 Eleganza Alexandria, Ontario, Canada

[Ken Henderson]

Well, Carl P. knew where to find the seal spec: Page 512 of the Assembly
Manual (bdub has it). Turns out the metal portion of the seal should be
left 0.025"-0.045" proud of the hub. Since we don't have a dimensioned
drawing of the seal nor of the assembly, we can't be sure of the
significance of that information. However, since I intend to make a seal
seating tool before I do them again, to be sure I observe that
specification, I'll be comfortable using the Chicago Rawhide seals I have:
If 0.26" is adequate clearance, then I must assume that's based on the
seal being seated with only 0.025" proud. So, I've got
0.045"-0.026"=0.019" tolerance available. That means that a 0.019"
deflection of the seal should be safe -- none of those I have deflect
anywhere near that much.

I will, of course, check the other features of the assembly to be sure this
hypothesis is correct.

There was another interesting bit of information in the reference: It's
specified that the wheel must be rotated at least 3 times during the
tightening and adjusting of the wheel bearing. That's a practice I've had
for 60+ years, but this is the first time I recall seeing it in any GMC
manual.

I've temporarily posted the relevant portion of the reference here:
https://drive.google.com/file/d/0B3XquSIYjDleenNDM1BHQlNHa1E/view?usp=sharing

My seal seating tool will simply be a steel disc slightly larger than the
outer diameter of the seal, with a recess in one side of 0.40" to receive
the seal. That means I'll be 0.005" shy of the minimum seating of the
seal, and have 0.014" of "safety factor".

Ken H.

On Mon, May 29, 2017 at 5:51 PM, James Hupy <james...@gmail.com> wrote:

> Ken, you are absolutely correct. Do not seat the seal below the outer part
> of the hub casting. Leave it a bit "proud" meaning sticking out a bit for
> insurance purposes. Jwid.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>
>

[rich...@comcast.net]

I will call SKF tomorrow and get a dim drawing. Pass it along to the group. It is possible that SKF changed their internal spacing, as all the information in their seal catalog describes only applications where the seal is treated as a stand alone assembly, and not as a part (of a larger assembly). I'll turn a few seal installation tools, this weekend.

----- Original Message -----

[John R. Lebetski]

I think I kept the box from the SFK seal from last year and will see if same number. IIRC the fail made is that the wrong one has the metal touching
the bearing resulting in metal particles in the rollers. If it were just the rubber wearing and not sealing that would almost be better.
--
John Lebetski
Woodstock, IL
77 Eleganza II

[Ken Henderson]

John,

IIRC, you're thinking of the front wheel bearing seal. From the drawing I
posted, it appears virtually impossible for the metal to touch the
bearing. But the rubber is separated from it only by about the distance
the seal should be left proud of the hub.

https://drive.google.com/file/d/0B3XquSIYjDleenNDM1BHQlNHa1E/
view?usp=sharing

Ken H.

On Tue, May 30, 2017 at 9:19 AM, John R. Lebetski <gransp...@gmail.com>
wrote:

> I think I kept the box from the SFK seal from last year and will see if
> same number. IIRC the fail made is that the wrong one has the metal touching
> ​ ​
> the bearing resulting in metal particles in the rollers. If it were just
> the rubber wearing and not sealing that would almost be better.

[Richard]

Ken,
I opened a can of worms for myself when I took a look at someone's coach after the GMCMI. There was too much play in the passenger rearmost wheel,
and that lead to discovering a loose bearing cup, broken brake shoes, an out of round drum on it's last legs, etc.

Trying to put it back together, I'm trying to locate seals that pass the 1/4" test and after hitting several auto parts stores and opening a dozen or
more boxes from several different brands, found that none of them passed, or were even that close. From the drawing in the manual it appears as you
say, that there's no way the metal could contact the bearing. So where did the 1/4" test come from? Does it matter?

Richard V.

Ken Henderson wrote on Tue, 30 May 2017 09:37

> John,
>
> IIRC, you're thinking of the front wheel bearing seal. From the drawing I
> posted, it appears virtually impossible for the metal to touch the
> bearing. But the rubber is separated from it only by about the distance
> the seal should be left proud of the hub.
>
> https://drive.google.com/file/d/0B3XquSIYjDleenNDM1BHQlNHa1E/
> view?usp=sharing
>
> Ken H.
>

> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org


--
'77 Birchaven TZE...777

[Bruce Hislop]

Richard,
The issue occurs when the seal housing is driven in flush with the hub housing. The trick is to leave the seal housing sitting slightly proud of the
hub as shown in the diagram below:

https://drive.google.com/file/d/0B3XquSIYjDleenNDM1BHQlNHa1E/view

Dave Lenzi makes a tool to install the seal to the proper depth.

--
Bruce Hislop
ON Canada

77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end

[Johnny Bridges via Gmclist]

I bought four that fit last year. Two were SKF, the other two were CarQuest boxed. Both had the same number stamped in the metal... not the part
number. The SKF ones had orange sealer painted on the outside, the CarQuest didn't. Obviously from the same source though.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

[Ken Henderson]

Richard,

What Bruce said.

Ken H.

Trying to put it back together, I'm trying to locate seals that pass the
> 1/4" test and after hitting several auto parts stores and opening a dozen or
> more boxes from several different brands, found that none of them passed,
> or were even that close. From the drawing in the manual it appears as you
> say, that there's no way the metal could contact the bearing. So where
> did the 1/4" test come from? Does it matter?
>

[Rob Mueller]

Bruce,

It should be noted that Dave found a supplier that provided seals that met HIS requirements THEN manufactured the tool to install
them.

The tool may or may not work with Chicago Rawhide / SKF or seals made by other manufacturers.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Bruce Hislop
Sent: Friday, April 20, 2018 7:16 AM
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test

Richard,
The issue occurs when the seal housing is driven in flush with the hub housing. The trick is to leave the seal housing sitting
slightly proud of the hub as shown in the diagram below:

https://drive.google.com/file/d/0B3XquSIYjDleenNDM1BHQlNHa1E/view

Dave Lenzi makes a tool to install the seal to the proper depth.

Bruce Hislop

[John Wright]

This issue was originally brought up by Dave Lenzi at the Fall 2010 DuQuoin
Convention where he had discovered several sets of rear bearings had an
issue with metal in the grease. Dave said there were 2 manufactures that
were OK. They are the Chicago Rawhide 3857731 and the SKF 21771. The SKF
is sold by NAPA.

https://www.napaonline.com/en/p/NOS21771?interchange=1

http://www.gmcmhphotos.com/photos/general-pictures/p45146-rear-bogy-seal.html

J.R. Wright
GMC Great Laker
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 30' Stretch
75 Avion (Under going Frame up Restoration)

[Rob Mueller]

JR,

At last falls GMCMI Convention in Elkhart, Dave showed me that the Chicago Rawhide / SKF 21771 had problems as well which is why he
found a source that was OK and produced the installation tool.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808



-----Original Message-----

From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of John Wright
Sent: Friday, April 20, 2018 10:50 AM
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test

This issue was originally brought up by Dave Lenzi at the Fall 2010 DuQuoin
Convention where he had discovered several sets of rear bearings had an
issue with metal in the grease. Dave said there were 2 manufactures that
were OK. They are the Chicago Rawhide 3857731 and the SKF 21771. The SKF
is sold by NAPA.

https://www.napaonline.com/en/p/NOS21771?interchange=1

http://www.gmcmhphotos.com/photos/general-pictures/p45146-rear-bogy-seal.html

J.R. Wright
GMC Great Laker
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 30' Stretch
75 Avion (Under going Frame up Restoration)

[gene Fisher]

Read here
http://gmcmotorhome.info/front.html#ZERK

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Richard]

Mr ERFisher wrote on Fri, 20 April 2018 14:39
> Read here
> http://gmcmotorhome.info/front.html#ZERK


Hello Mr ERF. That link seems to be for the front wheel seal, not the rear. Is there another one for the rear?

Richard
--
'77 Birchaven TZE...777

[Richard]

USAussie wrote on Fri, 20 April 2018 10:10

> Bruce,
>
> It should be noted that Dave found a supplier that provided seals that met HIS requirements THEN manufactured the tool to install
> them.
>
> The tool may or may not work with Chicago Rawhide / SKF or seals made by other manufacturers.
>
> Regards,
> Rob M.

Rob,
I haven't found an SKF seal that passes the 1/4" test, and I'm beginning to feel that it's a fool's errand trying to find one.

Would I be off-base assuming that one could measure the clearance of the rubber seal and simply add the difference that it's short to the spec for how
proud the seal sits? That is, if instead of .250" clearance under the rubber there's only .220" could I add the .030" difference to the spec'd .025"
to .045" proud seal set? ie, set the seal .055" to .075" proud?

Is this simply a measure the seal and modify the depth of set situation? That would make my life simpler and piss off far fewer auto parts people!

Thanks.

Richard
--
'77 Birchaven TZE...777

[Richard]

richshoop wrote on Mon, 29 May 2017 23:14

> I will call SKF tomorrow and get a dim drawing. Pass it along to the group. It is possible that SKF changed their internal spacing, as all the
> information in their seal catalog describes only applications where the seal is treated as a stand alone assembly, and not as a part (of a larger
> assembly). I'll turn a few seal installation tools, this weekend.

Rich,
I called SKF yesterday and the tech rep, while helpful, was unable to provide information on their seal's designed clearance, or a measured drawing,
so there's no way of knowing if recent SKF seals' failure to meet our clearance criteria is by design.

If you could get more information from SKF I'd love to see a dimensioned drawing.

Richard

--
'77 Birchaven TZE...777

[James Hupy]

I have noticed quite a bit of difference in the shoulders on different
spindles. Some protrude towards the threaded end more than others do. That
would place the shoulder close to the seal in some situations. And would be
the reason for interference in some situations.

Jim Hupy
Salem, Or
78 GMC ROYALE 403

[Ken Burton]

Mr ERFisher wrote on Fri, 20 April 2018 13:39
> Read here
> http://gmcmotorhome.info/front.html#ZERK

I thought we were talking about rear wheels.

I guess that I'm confused.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Rob Mueller]

Richard,

Review this drawing:

http://www.gmcmhphotos.com/photos/skf-21771-rear-seal-fails-test/p63893-rear-axle-seal.html

Note the position of the seal on the spindle. The problem arises when the seal comes in contact with the inner race of the bearing.

I guess you could set the seal to 0.055 to 0.070 proud and then coat it with grease and put the hub on until the inner bearing seats
on the spindle, then pull it straight off.

Look at the spindle and see where the grease is on the spindle.

I don't know if this will work or not but it's the only way I could come up with to see where the seal rode.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808



-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Richard
Sent: Friday, April 20, 2018 2:49 PM
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test

Rob,

I haven't found an SKF seal that passes the 1/4" test, and I'm beginning to feel that it's a fool's errand trying to find one.

Would I be off-base assuming that one could measure the clearance of the rubber seal and simply add the difference that it's short
to the spec for how proud the seal sits? That is, if instead of .250" clearance under the rubber there's only .220" could I add the
.030" difference to the spec'd .025" to .045" proud seal set? ie, set the seal .055" to .075" proud?

Is this simply a measure the seal and modify the depth of set situation? That would make my life simpler and piss off far fewer
auto parts people!

Thanks.
Richard