From: Ron (rojoha@attbi.com)
Date: Sun Aug 25 2002 - 09:27:46 PDT
When I pulled my rears due to oil leaks past the inner seals, I found
little "rabbit turds" of grease on the top of the axle between the bearings
and inside the hub. The 'turds' were created by blobs of grease being rolled
inside the hub in the oil inside the hub.The bearings had all of the grease
washed out of the outer bearing and not much left in the inner bearing.
So, greasing the bearings and leaving the outer seals off seems
counterproductive. If the seals could hold oil that well, they wouldn't leak
out on the inside of the wheels at all, right?
Most common cause of failure of the inner seals is the little piece of
cork being left out that goes into the keyway under the outer bearing and is
compressed into place by the tang on the outer seal. This allows oil into
the hub area in the first place. Again, the devil is in the details....
In 2 of the PS monthlies I've seen, one in the early seventies, and
again in the early 80's was a little blurb to the M35 mechs to make sure
they made sure they put these cork pieces in to avoid early seal failure. It
was also in a multi page MWO or TB that I can't seem to find at the moment
(lost in the
network hell on one of my machines).
Looking a little deeper, I came across this....
from TM 9-8000 PRINCIPLES OF AUTOMOTIVE
VEHICLES section 19-11, Para a) Synthetic rubber seals, "Fig 19-4
illustrates the effect of pressure on lip seals. Internal pressure developed
during operation forces the sealing lips tighter against the rotating shaft.
This type of seal will only operate effectively against fluid pressure from
one direction."
This would tend to explain why they use two seals. The inner seal keeps
water from entering the hub from outside. The outer seal keeps the oil from
reaching the inner seal and leaking out. You use grease on the bearings
because it tends to stay put in the hub if it does get flung off. The seals
at opposite end of the hub are there only to keep out OUTSIDE water, but
this requires the outer oil seal to protect the inner seal.
That make sense?
Ronzo
----- Original Message -----
From: <MVTrucker@aol.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Sunday, August 25, 2002 8:57 AM
Subject: Re: [MV] 2 1/2 ton rear wheel seals
> Rick,
> Interesting question and I'm looking forward to the responses.
> Years ago when I was doing my first seal installation, I
> stopped in to our local National Guard motor pool to ask
> some questions. What a learning experience! They pack
> the bearings with plain old chassis grease, the yellowish
> stuff, on the initial installation, then leave the outer seal
> out so the gear lube takes care of the bearings. I still
> pack the bearings with blue or red grease and install both
> seals. I'm not so sure that the inner seal would hold up
> very long against the light (compared to grease) gear
> lube.
> Joe Young
> www.joeyoung.com
>
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