RV Bearing Service Part Two: The Wrong Grease Seal That Could Have Caused a Major Failure
In Part One, I explained a simple rule for RV bearing and brake service:
If you’re guessing, you’re doing it wrong.
Yesterday, a routine mobile trailer bearing repack provided a perfect real-world example of why measurements matter.
The trailer had previously been serviced by a nationwide RV dealer chain. The owner believed the wheel bearings had been properly repacked and the trailer was ready to travel.
Once I pulled the hubs, however, I discovered something that could have eventually caused grease contamination, reduced braking performance, bearing damage, or a roadside breakdown.
Three of the trailer’s four wheels had the wrong grease seals installed.
A Routine Trailer Bearing Repack Uncovered a Serious Problem
This job started as a normal tandem-axle trailer bearing repack and brake inspection.
As part of my standard procedure, I removed each hub, cleaned and inspected the wheel bearings, examined the races, inspected the electric trailer brakes, and prepared to install new grease seals.
Before pressing a new seal into the hub, I test-fit the seal on the axle spindle.
That small step matters.
The seal should fit securely around the spindle’s seal journal. When I test-fitted the expected Dexter 10-36 grease seal, it felt wrong. It was looser than it should have been.
Somebody who was working from assumptions might have installed it anyway.
Instead, I stopped and measured the spindle with a digital caliper.
The seal journal measured approximately 2.125 inches.
That measurement told me this trailer did not use a Dexter 10-36 grease seal. It required a Dexter 10-10 grease seal.
Dexter 10-10 vs. 10-36 Grease Seal Dimensions
The Dexter 10-10 and 10-36 trailer grease seals look very similar, and both commonly have an outside diameter of approximately 3.376 inches.
The critical difference is the inside diameter:
Dexter 10-10 grease seal: 2.125-inch inside diameter
Dexter 10-36 grease seal: 2.250-inch inside diameter
A 10-36 seal installed on a 2.125-inch spindle is approximately one-eighth of an inch too large at the sealing surface.
That is not “close enough.”
The seal’s inner lip must maintain proper contact with the spindle. If the seal is too large, it cannot reliably contain the wheel-bearing grease. Grease can escape from the back of the hub and contaminate the trailer’s brake shoes, brake magnet and drum.
Once grease gets into an electric trailer brake assembly, braking performance can drop dramatically.
Three Parts Stores—and Still No Correct Trailer Seal
Once I confirmed the measurement, I needed to locate the correct 10-10 seals.
I visited three different parts stores. None of them had anything close to the seal I needed.
That is another challenge with professional mobile RV and trailer repair: the correct part is not always sitting on the shelf at the nearest automotive parts store. Sometimes the job requires knowing exactly what you are looking for—and knowing where to find it.
I eventually located the correct 10-10 grease seals at Iron Bear Trailer in Denver, Colorado.
These guys are excellent.
If you need a trailer part, Iron Bear Trailer either has it, knows exactly what it is, can order it, or can build the axle you need. Having access to a knowledgeable trailer-parts supplier can make the difference between completing a repair properly and installing something that merely looks close.
The Previous Bearing Repack Used Two Different Seal Sizes
When I returned to the trailer, I spoke with the owner about its service history.
The owner told me that a nationwide RV Dealership with a service department — one most RV owners would recognize—had performed the previous bearing repack approximately three years earlier.
After inspecting all four hubs, I found:
Three wheels had Dexter 10-36 grease seals installed
One wheel had the correct Dexter 10-10 grease seal
All four wheels used the same 2.125-inch seal journal
The previous service provider had apparently installed whatever seals were available and called the job complete
The trailer did not have three different spindle sizes and one correct spindle.
It had three incorrect seals and one correct seal.
That is not a proper RV bearing repack. That is guessing.
The Trailer Owner Was Extremely Fortunate
Fortunately, the owner had not used the trailer very much during the three years since the previous bearing service.
That limited use may have prevented the problem from becoming a major wheel-end failure.
An oversized grease seal may allow grease to escape from the back of the hub. That grease can reach the brake shoes, magnet and drum. Once the braking surfaces become contaminated, cleaning may not always be enough. Brake assemblies or drums may need to be replaced.
Continued operation can lead to:
Grease-contaminated trailer brakes
Reduced braking power
Uneven trailer braking
Overheated hubs and drums
Premature bearing or race failure
Damaged axle spindles
Expensive roadside repairs
Possible wheel-end failure
A bearing repack should prevent these problems—not create them.
Why Every RV Grease Seal Should Be Verified
A professional RV bearing repack involves more than removing old grease and forcing new grease into the bearings.
The complete trailer wheel-end system should be inspected and measured.
That includes:
Cleaning and inspecting the inner and outer wheel bearings
Inspecting bearing rollers for pitting, scoring and discoloration
Inspecting the bearing races
Measuring brake-shoe thickness
Inspecting the electric brake magnets
Checking brake wiring and connections
Measuring the brake drums when necessary
Identifying the correct grease seal
Measuring the spindle’s seal journal
Test-fitting the new seal before installation
Properly packing the bearings
Setting the correct bearing preload
Adjusting and testing the trailer brakes
A part number from a previous invoice is not enough.
The old seal is not always proof of the correct replacement—especially when the previous technician installed the wrong seal.
The spindle measurement tells the truth.
“It Fits in the Hub” Does Not Mean It Fits the Axle
Both the 10-10 and 10-36 grease seals may press into the same hub because they share a similar outside diameter.
That is what makes this mistake easy to miss.
A technician can press a 10-36 seal into the hub, reinstall the hub and believe the job is complete. But if the seal’s inside diameter is too large for the spindle, the sealing lip cannot do its job.
The seal must fit both:
The seal bore inside the hub
The seal journal on the axle spindle
Checking only one measurement is incomplete service.
Mobile RV Bearing and Brake Service in Northern Colorado
At Colorado RV Service, we provide mobile RV bearing repacks, trailer brake inspections and wheel-end service throughout Northern Colorado and the Colorado Front Range.
We serve RV and trailer owners in and around:
Berthoud
Longmont
Loveland
Estes Park
Boulder
Fort Collins
Northern Colorado
Surrounding Front Range communities
We come to your RV, travel trailer, fifth wheel, cargo trailer or utility trailer and perform the service where it is parked.
Our goal is not to tell you that everything “looks okay.”
Our goal is to inspect it, measure it and show you what is actually happening inside each wheel end.
The Lesson: Never Guess at a Trailer Grease Seal
This trailer came in for routine maintenance. It left with the correct 10-10 grease seals installed and the wheel bearings serviced properly.
The problem was found because one seal felt slightly loose—and instead of ignoring that feeling, I measured it.
That is the difference between replacing parts and performing professional trailer wheel-bearing service.
A 10-10 seal and a 10-36 seal may look almost identical on the workbench. On the wrong spindle, however, that one-eighth-inch difference can lead to grease-contaminated brakes and an expensive roadside failure.
The owner trusted the previous service provider and was told the job was done.
Three incorrect seals said otherwise.
If you’re guessing, you’re doing it wrong.
Schedule Mobile RV Bearing and Brake Service in Colorado
If your RV or trailer is due for a wheel-bearing repack, brake inspection or complete wheel-end service, contact Colorado RV Service.
We provide professional mobile RV repair and maintenance throughout Northern Colorado, including Berthoud, Longmont, Loveland, Estes Park, Boulder and surrounding communities.
Colorado RV Service
303-525-7894
We come to you. We measure the parts. We install what actually belongs there.
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