| Inner front wheel bearing seal [message #81301] |
Wed, 21 April 2010 09:15  |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
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Well, I had about 25K miles on the coach since I looked all of the wheel bearings, so decided it was time for a look see. Bearings, seals and shoes on the rear were perfect, So I just cleaned, repacked and put them back together.
The fronts however...a different story. Pulled left front apart and found nothing of significance to report. Took the right side apart and first noticed that the grease was darker in color than the left side. After cleaning, the bearings and races looked quite normal...then my finger caught a sharp edge on the inner bearing roller cage. The edge of the cage indicated that it was rubbing on something, so I looked at the seal. Sure enough, evidence of a slight rub between the seal and the bearing cage.
For those of you that were at the last GMCMI rally in Montgomery, and attended Dave Lenzi's session on front wheel bearings, you may recall that he and others had noticed a change in the way they manufacture that inner seal (the one that seals against the CV joint). The inner portion of the steel portion of the seal, instead of being just straight, in some cases has been manufactured with a slight curl-up lip. This lip is just high enough that, when set properly can make contact with the bearing cage. This contact makes for steel shavings that can get into the inner bearing and cause failure. That is why the grease on my left side bearings looked darker than the right...it has some steel shavings mixed in with it. Fortunately, the contact was quite minor and did not create enough to cause a failure, or even any noticeable damage to the bearings or races.
I talked with Dave some about this. It seems that National is *one* of the only brands making the correct seal for our GMC. It is National Seal #5123. This seal does NOT have the turned up lip that can cause us problems. Things have changed since I did these bearings 6 yrs ago, including the way we install the seal. Had I installed the seal (a Chicago Rawhide seal with the lip) using todays method of referencing off of the knuckle, the seal would have been deep enough that it would have made significant contact with the bearing...perhaps leading to catastrophic failure.
My point, if you are not sure of the seals that you installed last time, maybe you better check them. I have posted pics of the two seals...my old seal with the "lip" and the new seal National #5123 on the GMC photo site. It may be hard to make out. It is hard to see, but the difference can be "felt".
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5446
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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