Bearing Failure

Courtesy of Patrick Flowers

The following few photographs depict the results of improper front wheel bearing maintenance and why this is so critical on the GMC motorhomes. This incident occurred on my father's 1976 Eleganza II with approximately 86,000 total miles. He purchased the coach five years ago and was assured by the previous owner that it had "new front wheel bearings". In the past five years he's driven the coach nearly 25,000 relatively trouble-free miles. We were planning to service or replace(as necessary) the front wheel bearings within the next thirty days.

Returning home on the trip previous to the one on which the failure occurred, he heard a noise which he described as "sounding like a tire separating". He immediately pulled off the road, but found nothing wrong. The sound did not recur until approximately 250 miles later, when the bearing failed catastrophically. When the bearing failed, it made the same sound he had heard previously. Again, he pulled off the road immediately and found smoke billowing out from under the right front wheel.

This photo shows the hub and steering knuckle in an approximation of their formerly assembled positions. All the bearing rollers were ejected from the hub during the failure. It is possible to lift the hub out of the knuckle with little effort.

Here is the knuckle with the hub removed. The outer bearing races and spacer are still intact, although partially worn away. The knuckle appears to be rebuildable, which will save my father the "core" charge.

This is the hub with the knuckle removed. The remains of the inner bearing races are visible. This hub also appears rebuildable, but the races will probably need to be cut off the hub shaft.

This is a close-up of the inner surface of the steering knuckle. Visible at the top of the knuckle center opening are wear marks left by the outer CV joint housing. When a front wheel bearing fails catastrophically, the outer CV housing is all that keeps the front wheel from departing the coach.

The outer CV joint. The intense heat after the bearing failure melted the boot off the joint. The boot clamp is still in place and is visible as a rusty streak across the joint housing.

What can be learned from this?

While it is common knowledge among GMCers that front wheel bearing maintenance at 25,000 mile intervals is critical. It is equally critical to establish a baseline. My father assumed that the previous owner had replaced the front wheel bearings just prior to selling the coach and that the work was done properly.
If you're not sure when the work was done, who did the work and whether it was done properly, then assume the bearings need to be serviced immediately and that it's not safe to drive the vehicle.
Don't let the cost of the tools necessary to service the bearings deter you from doing the work. The cost to my father in parts alone would have paid for two sets of bearing service tools with enough left over for a very nice night out on the town.
At the risk of being redundant, do not under any circumstances or for any reason procrastinate on this issue.
Stop immediately upon hearing any "tire" noise and check the hub temperature in addition to tire temperature.

A description of the procedure and tools for servicing the front wheel bearings can be found at Front Wheel Bearing Service.

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