Wheel bearing hot spots/blue discoloration

[KnowNuthin]

While repacking the wheel bearings on our FW I noticed a discolored portion on the inner race of a couple of the inner bearings...there is a corresponding discoloration of the axle spindle where the bearing was sitting (the bearing didn't spin... the hot spot created in the bearing went right through to the spindle)

When I first removed the dust cap I could easily turn the castle nut by hand (the cotter pin was in place so the castle nut only turned a few degrees but it turned easily). Last time I packed the bearings I snugged the castle nut until the brake drum began to get harder to spin, then I backed off the nut a quarter turn and installed the cotter pin. Is this the correct method of preloading the bearings on a FW?

None of the bearings were "dry"... I needed to use several paper towels to remove the old grease that was on, in and around each bearing (I use Lucas Red Tacky grease for bearings).

The Lippert axles on my trailer have the "bearing buddy" design, however, I didn't use this feature after I hand-packed the bearings last time. (Grand Design had an issue with grease getting past the seals and contaminating the brakes when the axles were greased at the factory using the bearing buddy)... I was one of the ones with "greased brakes"... I upgraded to auto-adjusting brakes...

I've replaced many roller bearings on older American made cars... never had an issue... so I'm not really sure what the heck I'm doing wrong on our FW... any ideas?

[Gdetrailer]

KnowNuthin wrote:
Last time I packed the bearings I snugged the castle nut until the brake drum began to get harder to spin, then I backed off the nut a quarter turn and installed the cotter pin. Is this the correct method of preloading the bearings on a FW?...



...I've replaced many roller bearings on older American made cars... never had an issue... so I'm not really sure what the heck I'm doing wrong on our FW... any ideas?

The section in bold in your comments is the issue.

You overtightened the bearings.

Unlike auto wheel bearings, trailer axles do not require "preloading", trailer bearings are supposed to run a bit "sloppy".

In fact, if you observe the castleations on a trailer nut vs a auto you will notice the trailer nut has less castleations..

The correct procedure is outlined in the Dexter axle service manual..

HERE

See pages 52-53.

From those pages..

"Bearing Adjustment and Hub Replacement
If the hub has been removed or bearing adjustment is required,
the following adjustment procedure must be followed:

1. After placing the hub, bearings, washers, and spindle nut back on the axle spindle in reverse order as detailed in the previous section on hub removal, rotate the hub assembly
slowly while tightening the spindle nut to approximately 50 Ft. Lbs. (12" wrench or pliers with full hand force.)

2. Then loosen the spindle nut to remove the torque. Do not rotate the hub.

3. Finger tighten the spindle nut until just snug.

4. Back the spindle nut out slightly until the first castellation
lines up with the cotter key hole and insert the cotter pin.

5. Bend over the cotter pin legs to secure the nut.

6. Nut should be free to move with only restraint being the
cotter pin."

Notice the section in bold type..

Basically a 12" long wrench hand tightened unitl the nut stops moving, then with drum not rotating back off the nut slightly to release the torque.

The finger tighten nut.

If you can't get the cotter pin hole to align with a opening in the nut, back off the nut to the nearest opening from hand tight position.

Under no circumstance should you tighten the nut to get the cotter pin through.

This often results in the bearings fitting a bit sloppy or loose but on a trailer this is OK as you do not need to be precise like a auto.

[Lynnmor]

Here you can learn a simple way to post photos.

All common brands of trailer axles use the same adjustment and most parts are interchangeable.

I still think that you don't have a heat issue, go to this site for some information.

[KnowNuthin]

Thanks for the replies…

I can’t post pics here as I don’t have a photo hosting site to copy a url from…

Looking at the Dexter site… it could be I had too much axial play as I backed off on the nut more than they recommend… (I’ll assume my Lipert axles are adjusted the same way)

I don’t think the bearing was spinning as the Localized heat and discoloration transferred through the race to the spindle (it’s on the bottom of the spindle only… and the race and spindle is only blue in one rather small spot… )

[Lynnmor]

A photo would help. It is normal for harmless fretting corrosion to appear where the bearing meets the spindle, applying a thin coat of grease to the spindle will help reduce that. All bearings of this type are adjusted the same way, not just fifth wheels. There is to be a very small amount of play in the bearings, you don't just back off a certain amount.

See page 56

[Fisherman]

While repacking the wheel bearings on our FW I noticed a discolored portion on the inner race of a couple of the inner bearings...there is a corresponding discoloration of the axle spindle where the bearing was sitting (the bearing didn't spin... the hot spot created in the bearing went right through to the spindle)

The only thing I can think of is that the race was spinning on the spindle which it should not. Possibly a small bit of crud stuck between the rollers prevented them from going around until they were dislodged going forward/backwards.

[azdryheat]

Perhaps the race wasn't fully seated.