INSTALLATION INSTRUCTIONS
THREADED AND BOLT-ON ALUMINUM OIL CAP
K21-303-00:
K21-302-00:
K21-259-00:
K21-301-00:
K21-304-00:
K21-305-00:

THREADED CAP INSTALLATION

5,200 - 8,000 LBS. THREADED CAP
9,000 - 10,000 GD LBS. THREADED CAP
9,000 - 12,000 LBS. BOLT-ON CAP
10,000 HD - 15,000 LBS. THREADED CAP
10,000 - 16,000 LBS. THREADED CAP
10,000 - 16,000 LBS. THREADED CAP

1. Drain oil from existing cap and properly dispose of oil. Caps utilizing
grease do not need drained before cap removal.
2. Remove the existing cap, using a 2.5” socket, 6-point and a ratchet or
breaker bar. Then unscrew the cap counterclockwise while keeping the
hub stationary.

BEFORE BEGINNING, INSPECT THE NEW CAP. IF DAMAGE IS
PRESENT, STOP PROCESS IMMEDIATELY AND CONTACT SUPPLIER
FOR REPLACEMENT.

3. Inspect hub and cap mating surfaces for lubrication and debris. Wipe
clean using a clean cloth, rag, or plastic paint scraper. Be careful not to
damage the sealing surfaces when scraping off stubborn dirt material.

IT IS THE CUSTOMER’S RESPONSIBILITY TO ENSURE THAT THE CAP
MATCHES THE HUB SPECIFICATIONS FOR THE TRAILER.

4. For grease applications, visually inspect hub opening for presences of
grease and it’s condition. If grease is present and in good condition,
continue to step 5. If there is minimal to no grease or the grease is
contaminated, bearings with need repacked following instructions
in Dexter’s service manuals. Do not proceed with installation without
completing repacking.

CAUTION
DO NOT LIFT OR SUPPORT THE TRAILER ON ANY PART OF THE
AXLE OR SUSPENSION SYSTEM. NEVER GO UNDER ANY TRAILER
UNLESS IT IS PROPERLY SUPPORTED ON JACK STANDS WHICH
HAVE BEEN RATED FOR THE LOAD. IMPROPERLY SUPPORTED
VEHICLES CAN FALL UNEXPECTEDLY AND CAUSE SERIOUS
INJURY OR DEATH.

5. Apply a thin layer of oil on the hub side of the o-ring.
O-ring

O-ring

DEXTER REQUIRES MAINTENANCE EVERY 12 MONTHS OR 12,000
MILES. IF YOU ARE AT A MAINTENANCE INTERVAL, BE PREPARED TO
DISASSEMBLE WHEEL END AND REPACK BEARINGS.
6. Position the cap over the hub opening and ensure threads are aligned
to prevent cross-threading. Hand-tighten clockwise until snug.

RECOMMENDED TOOLS
▪
▪
▪
▪
▪

6 mm Allen socket
Ratchet or breaker bar
Clean, lint-free cloth or rag
Clean plastic paint scraper
Lubricant

7. Using a 2.5” socket, torque the cap to the specification indicated on
the cap.
8. For standard grease applications, installation is complete. For oil
applications, continue to oil lubrication section.

BOLT-ON CAP INSTALLATION

THREADED ONLY:
▪ 2.5” socket attachment, 6-point
▪ 5 – 40 ft.-lbs. range torque wrench
BOLT-ON ONLY:
▪ 5 mm Allen socket attachment
▪ 5 – 10 ft.-lbs. range torque wrench

1. Drain oil from existing cap and properly dispose of oil. Caps utilizing
grease do not need drained before cap removal.
1. Remove the existing cap, using the 5 mm Allen socket and a ratchet or
breaker bar. Then unbolt the cap while keeping the hub stationary.

LUBRICATION SPECIFICATIONS
▪ SAE 90, SAE 80W-90, or SAE 75W-90 oil
▪ Dexter Grease (088-012-00) or equivalent lithium NLGI #2 complex

©2023 DEXTER AXLE COMPANY | WWW.DEXTERAXLE.COM

2. Inspect hub and cap mating surfaces for lubrication and debris. Wipe
clean using a clean cloth, rag, or plastic paint scraper. Be careful not to
damage the sealing surfaces when scraping off stubborn dirt material.
3. For grease applications, visually inspect hub opening for presences of
grease and it’s condition. If grease is present and in good condition,
continue to step 4. If there is minimal to no grease or the grease is
contaminated, bearings with need repacked following instructions
in Dexter’s service manuals. Do not proceed with installation without
completing repacking.

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OIL LUBRICATION

4. Align the bolt holes in the cap and gasket then align with hub.
Gasket

The cap can be filled with oil from either the front or side plug.

Gasket

1. Gently remove the front or side plug by hand.
2. Fill cap with oil matching the indicator fill lines.
3. If using front plug, replace plug into the cap and skip to step 6.
4. If using side plug, apply Loctite® 516/517 sealant to the threads before
reinstalling. Failure to reapply the sealant could result in oil leaks.
5. Replace side plug and torque 5–6 ft-lb. using a 6 mm Allen socket.

5. Ensure bolt is precoated and the lock washer installed. If not, install
lock washer then apply Loctite® 516/517.

Side Plug

6. Begin to thread bolts by hand, through the assembly and then handtighten clockwise until snug.

Lock Washer
Bolt

6. After filling, spin the hub and recheck the oil level through the level
indicators on the clear viewing lens. If level has changed, there may
be a gap between the hub and seal.
7. Using a clean cloth or rag, wipe off any excess lubricant or dirt around
the cap.

7. Using a 5 mm Allen socket, torque the bolts to 6 – 8 ft.-lbs.
8. For standard grease applications, installation is complete. For oil
applications, continue to oil lubrication section.

SCAN FOR DEXTER’S
SERVICE MANUALS

SCAN FOR MORE
INFORMATION ON
DEXTER’S FORTRESS
PRODUCT LINE

©2023 DEXTER AXLE COMPANY | WWW.DEXTERAXLE.COM

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