| 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:
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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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