What Can Cause Hubs To Leak Grease Out Of Rear Seal?

Updated 12/03/2025 | Published 11/04/2025

Products Featured in This Question

Easy Grease Trailer Idler Hub Assembly for 2K Axles - 5 on 4-1/2 - Galvanized

(738)

$68.48

Grease Seal

(2371)

$12.82

Question:

I bought two hubs for my trailer. One works fine, the other leaks all the grease out the rear seal. The old hub and seal did not leak. I changed hubs to get lug studs instead of bolts. I pumped half a tube of grease out on the back side of the hub. Whats up with that?

asked by: Steve P

Expert Reply:

Hi Steve, thanks for reaching out and sharing those details. Based on what you described, it sounds like the issue is likely due to over-greasing the hub. When too much grease is pumped in, it can build excess pressure and force its way past the rear seal, which causes the leak you’re seeing.

For future reference, only a small amount of grease is needed to fully pack the bearings - usually just enough to fill the bearing cavity without creating pressure behind the seal. Over-filling can damage a perfectly good seal, even if everything was installed correctly.

We generally recommend just packing the hubs by hand and not adding additional grease into the zerk fitting. If you do add grease thru the zerk fitting, it should only be a small amount like 1-2 pumps tops.

I’d recommend cleaning out the excess grease, inspecting the rear seal for damage, and replacing it if needed. Once reassembled with the proper amount of grease, the hub should perform as expected. If you do end up needing a new seal, those are available as part # 10-9.

expert reply by: Jesse M

Jesse M.

12/1/2025

Hey Steve, did cleaning out the extra grease and checking the rear seal get your trailer hub working right again? Knowing how it turned out could help others dealing with the same leak issue.

Steve P.

12/1/2025

@JesseM It was the wrong size seal. You should mention in your ads that there are several sizes of seals so people can order the correct one.

Jesse M.

12/3/2025

@SteveP Thanks for the feedback. Trailer hub seals come in many sizes, which is why we list all the measurements and specs for the seals on the product page so the correct seal can be matched to the trailer’s hub. Verifying those specs against your existing seal or spindle is the best way to ensure the right fit. Typically using the casting number on the hub is a good way to find the exact specs for your bearings and seals.