| 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:
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Senior Member |
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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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