Rear bearing seals, still an issue

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,175
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Ontario Canada
Its been about 5 years and over 20K miles since the rear bearings were redone so its time to do them again.

I bought some new bearings and seals from a former GMCer a couple of years ago. The seals are 8974S in a National box. I tried the 1/4" clearance
trick and these fail. From my understanding, the seal will sit too close to the bearing and the rubber will touch the bearing causing it to get
damaged. Then the grease can leak out and toast the bearing.

Has anyone come up with a consistent good part number? or a work-around for a seals that fail the 1/4" test?

Thanks

--
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
 
Bruce,
You want to try and find the SKF 21771. These work, but you should still do the 1/4 inch test incase they have changed. Use some 1/4 inch copper tubing. They are available from NAPA and other auto parts supplies.

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

JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan

>
> Its been about 5 years and over 20K miles since the rear bearings were redone so its time to do them again.
>
> I bought some new bearings and seals from a former GMCer a couple of years ago. The seals are 8974S in a National box. I tried the 1/4" clearance
> trick and these fail. From my understanding, the seal will sit too close to the bearing and the rubber will touch the bearing causing it to get
> damaged. Then the grease can leak out and toast the bearing.
>
> Has anyone come up with a consistent good part number? or a work-around for a seals that fail the 1/4" test?
>
> Thanks
>
> --
> Bruce Hislop
> ON Canada
 
> Its been about 5 years and over 20K miles since the rear bearings were redone so its time to do them again.
>
> I bought some new bearings and seals from a former GMCer a couple of years ago. The seals are 8974S in a National box. I tried the 1/4" clearance
> trick and these fail. From my understanding, the seal will sit too close to the bearing and the rubber will touch the bearing causing it to get
> damaged. Then the grease can leak out and toast the bearing.
>
> Has anyone come up with a consistent good part number? or a work-around for a seals that fail the 1/4" test?
>
> Thanks

October 2015 we got SKF 21771 seals from NAPA and they passed the 1/4" test.
--
Wally Anderson
Omaha NE
75 Glenbrook
Megasquirt III injection
Bob Stone hydroBOOOOST
Manny reaction arm system
Branscombe Kelsey Hayes park brake
http://wallyandsue.blogspot.com/
 
I guess you read here .?
http://bdub.net/gmcmotorhome.info/rear.html

On Fri, May 26, 2017 at 6:11 AM Wally Anderson
wrote:

> > Its been about 5 years and over 20K miles since the rear bearings were
> redone so its time to do them again.
> >
> > I bought some new bearings and seals from a former GMCer a couple of
> years ago. The seals are 8974S in a National box. I tried the 1/4" clearance
> > trick and these fail. From my understanding, the seal will sit too close
> to the bearing and the rubber will touch the bearing causing it to get
> > damaged. Then the grease can leak out and toast the bearing.
> >
> > Has anyone come up with a consistent good part number? or a work-around
> for a seals that fail the 1/4" test?
> >
> > Thanks
>
> October 2015 we got SKF 21771 seals from NAPA and they passed the 1/4"
> test.
> --
> Wally Anderson
> Omaha NE
> 75 Glenbrook
> Megasquirt III injection
> Bob Stone hydroBOOOOST
> Manny reaction arm system
> Branscombe Kelsey Hayes park brake
> http://wallyandsue.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://bdub.net/gmcmotorhome.info/
Alternator Protection Cable
http://bdub.net/gmcmotorhome.info/APC.html
 
So, how do you remove the rear seals?
When removing the rear seal:
Remove axle nut and large washer
Remove outer bearing
Now thread axle nut back on shaft
With a jerk pull the tire and wheel off
That should capture the inner bearing and seal with no damage
This seal can be reused if not worn out.

> I guess you read here .?
> http://bdub.net/gmcmotorhome.info/rear.html
>
>
> On Fri, May 26, 2017 at 6:11 AM Wally Anderson

>

> > > Its been about 5 years and over 20K miles since the rear bearings were
> > redone so its time to do them again.
> > >
> > > I bought some new bearings and seals from a former GMCer a couple of
> > years ago. The seals are 8974S in a National box. I tried the 1/4"
> clearance
> > > trick and these fail. From my understanding, the seal will sit too
> close
> > to the bearing and the rubber will touch the bearing causing it to get
> > > damaged. Then the grease can leak out and toast the bearing.
> > >
> > > Has anyone come up with a consistent good part number? or a work-around
> > for a seals that fail the 1/4" test?
> > >
> > > Thanks
> >
> > October 2015 we got SKF 21771 seals from NAPA and they passed the 1/4"
> > test.
> > --
> > Wally Anderson
> > Omaha NE
> > 75 Glenbrook
> > Megasquirt III injection
> > Bob Stone hydroBOOOOST
> > Manny reaction arm system
> > Branscombe Kelsey Hayes park brake
> > http://wallyandsue.blogspot.com/
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://bdub.net/gmcmotorhome.info/
> Alternator Protection Cable
> http://bdub.net/gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
 
Thanks for the update. I wanted to find the latest info on this issue.

A member of our club called me to say he just bought a couple SKF-21771 from Napa today, and they pass the 1/4" test. I have 4 SKF-21771 coming in to
the local Napa.

FYI, I also checked the part numbers for the inner bearing and cup from Emery's numbers. They are a kit as a set BR35.

Thanks again,

--
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
 
If I had just waited till the end of the day, I came home to find my GMCMI spring mailing with the Parts Interchange.

The bearing seal issues are shown on page 9.

Lots of other good info in the front pages as well.

Thanks Kim and everyone involved with compiling and printing this great resource.

--
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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