Home » Public Forums » GMCnet » NAPA SKF-21771 rear bearing seal fails the 0.25" test
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318159 is a reply to message #318141] |
Mon, 29 May 2017 16:36   |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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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 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?
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318160 is a reply to message #318159] |
Mon, 29 May 2017 16:51 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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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
On May 29, 2017 2:38 PM, "Ken Henderson" wrote:
> 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
> 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?
>>
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> Unsubscribe or Change List Options:
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| Re: NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318161 is a reply to message #318156] |
Mon, 29 May 2017 17:35 |
ree_eric
Messages: 43
Registered: February 2004
Location: Alexandria, Ontario, Cana...
Karma: 0
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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 (parts) '75 Eleganza (TB, exhaust x-over blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler, aux vacuum, fuel tank sealing, rebuilt senders and new rubber, propane hot water heater.) Alexandria, Ontario, Canada
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318195 is a reply to message #318160] |
Mon, 29 May 2017 21:47 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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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 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
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318199 is a reply to message #318195] |
Mon, 29 May 2017 22:14 |
richshoop
Messages: 190
Registered: April 2017
Karma: 0
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Senior Member |
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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 -----
From: "Ken Henderson"
To: "gmclist"
Sent: Monday, May 29, 2017 7:47:35 PM
Subject: Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test
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 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
>
>
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| Re: NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #318217 is a reply to message #318141] |
Tue, 30 May 2017 08:19 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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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
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331109 is a reply to message #318218] |
Thu, 19 April 2018 23:19 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Senior Member |
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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 09:37John,
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;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| Re: NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331123 is a reply to message #318141] |
Fri, 20 April 2018 07:44 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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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
Foolish Carriage, 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
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331127 is a reply to message #331109] |
Fri, 20 April 2018 08:32 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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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?
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331130 is a reply to message #331119] |
Fri, 20 April 2018 09:10 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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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-bounces@list.gmcnet.org] On Behalf Of Bruce Hislop
Sent: Friday, April 20, 2018 7:16 AM
To: gmclist@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
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331137 is a reply to message #331109] |
Fri, 20 April 2018 10:49 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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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)
On Fri, Apr 20, 2018 at 12:19 AM, Richard wrote:
> 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] NAPA SKF-21771 rear bearing seal fails the 0.25" test [message #331138 is a reply to message #331137] |
Fri, 20 April 2018 10:53 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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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-bounces@list.gmcnet.org] On Behalf Of John Wright
Sent: Friday, April 20, 2018 10:50 AM
To: gmclist@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)
_______________________________________________
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Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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