Front Wheel Bearing (240z, 260z, 280z)

Figure 1. Front Wheel Bearing (Seal, Inner, and Outer)

Overview

• Your Z rolls along the road on tires and rims. In turn (pun), the rims roll on bearings.
• Bearings consist of two hardened rolling surfaces separated by rollers. These materials must be made of correctly hardened metals with exact tolerances to work properly and reliably.
• Lubrication is important to reduce friction (heat) that will distort and degrade the components.
• Bearings must be kept clean and free from debris. Dirt and debris will act as an abrasive if it contaminates the working area of the rollers and races.
• The powerful forces caused by every bump in the road, application of brakes, and side loading of tires while turning is coupled through the wheel bearings. They must be adjusted correctly to operate within the designed close tolerances to endure the literal pounding and twisting of the wheels.
• When installing bearings, it is crucial that the space between the roller bearings (front) (and often ball bearings) and races (hardened steel rings) is set correctly. If it is too tight, the wheel will bind and the bearings will overheat. If it is too loose, the wheel will jump around on the hub spindle. This will beat the bearings against the races causing them to deform, roll poorly, and generate vibrations that travel throughout the Z's metal structure.

Drawings

Figure 2. Front Wheel Bearing (Detail)

Figure 3. Front Wheel Bearing & Wheel (Cross Section)

Nissan Part Numbers

Replacement Parts

• Stock (Nissan)
  Outer Bearing & Race: 40215-A0100
  Inner Bearing & Race: 40210-A0100
  Inner Seal:           40232-A0101
  
• OEM (NTN)
  Outer Bearing:        NTN 4T-LM11949
  Outer Bearing Race:   NTN 4T-LM11910
  Inner Bearing:        NTN 4T-LMS7048
  Inner Race:           NTN 4T-LM67010
  
• Timken
  Outer Bearing & Race: TIMKEN SET2
  Inner Bearing & Race: TIMKEN Set6 (# LM67048 and Timken # LM6701)
  Inner Seal:           TIMKEN 1188S
  
• SKF
  Outer Bearing & Race: SKF BR2
  Inner Bearing & Race: SKF BR6
  Inner Seal:           SKF 18864 {#40232A0101}
  

Figure 4. Front Wheel Bearing Outer Bearing NTN LT-LM11949

Figure 6. Front Wheel Bearing Outer Race NTN LT-LM11910

Differences Between Years
Front Wheel Bearings: None  (Note: the hub shape changed in 07/73)

Figure 7. 1971 240z Front Hubs


Figure 8. 1977 280z Front Hubs

Maintenance/Service

• Reference Note:

  Over-tightening adjustable tapered roller bearings is a common error that can lead to premature failure. Tapered roller bearings on the front of RWD vehicles are never preloaded. They’re typically snugged up with no more than 15 to 20 ft.-lbs. of torque while rotating the wheel to make sure the bearings are seated. Then the adjustment nut is loosened 1/6 to 1/4 a turn and locked in place with a new cotter pin.
  
  As a rule, end play should be about 0.001” to 0.005.” Up to 0.010” of play in the front bearings may be acceptable on RWD vehicles.
  
  To avoid damaging a new bearing, the bearing inner race must be carefully pressed onto a shaft, and the outer race pressed into its bore. Hammering a bearing in place can result in the rollers or balls dimpling the bearing races and causing premature failure.
  
  Most bearings have about 0.001” of interference-fit built into an axle shaft or bearing bore, which means that these types of bearings must be pressed or driven into place. Tapered bearing cups or outer races should be driven in place using a special aluminum driver. In an emergency, an old bearing race cut through with a cutting disc will serve the purpose.
  

• Tips:
  - It is less-messy to place the bearing and grease inside a zip-lock baggie when packing the grease.
  - Cooling the race in a freezer prior to installation causes it to contract. This smaller size race facilitates a faster and easier insertion into the hub.

• Factory Service Manual Excerpts:
  - 1970 FSM Excerpt (PDF)
  - 1978 FSM Excerpt (PDF)
  
  
• Procedures:
  - Routine Tightening
  - Wheel Bearing Replacement on 1970 240z
  - Wheel Bearing Replacement on 1977 280z
  
  
• Tools:
  - fishing spring scale (to measure pre-load)
  - brass drift (to knock out races)
  - plastic bag (to grease bearing)
  - race drift (to press race into hub)
  - seal drift (to press seal into hub)
  - solvent (to clean hub & spindle)
  - torque wrench (to secure nut)
  - scotch brite pad (to clean spindle & hub)

Modifications/improvements

- Optimal Cotter Pin Installation
- Selecting Grease (Recommended: Wurth SIG 3000)

Part Restoration

N/A as the bearing is a non-serviceable part.

Performance/racing

Avoid "Made In China" parts as the quality varies and counterfeit parts are common. It is not a risk you (or your competition) want to deal with in a race.

Bearing Failure

Bearings fail/wear out from
- heat from friction (loss of lubrication or heat from improper installation pre-load)
- mechanical stress (improper installation or failure to maintain)
- material failure (defect in material or poor quality material)

Typically bearings fail slowly and do not leave you stranded on the road.

The common symptom of a failing bearing is a drone that is proportional to the rotational speed. The drone usually gets louder over the period of weeks as the bearing continues to slowly fail.
Initially the sound is barely perceivable (due to the masking effect of tire, exhaust, and engine noise) but it eventually increases in loudness to exceed these.
Due to the low frequency of the drone sound, it is sometimes difficult to pinpoint which wheel is droning. Having a passenger verify the location is helpful. Switching from driver to passenger while on a test drive is another trick to better locate.
Often with wheel bearings, the sound changes when you remove the load from the bearing thus turning right or left at reasonable speeds can shift the load and help identify which bearing is noisy. When turning, the outside bearing will load and drone louder when it is failing.

Another method for detecting a worn bearing is to jack the front wheels off the ground and spin each wheel while listening to the dust cap with a mechanic's stethoscope.

Of course the common trick to test for a loose wheel bearing is to jack the car off the ground and grab the wheel at 9 o'clock and 3 o'clock then rock to feel slope. Repeating by grabbing the wheel at 12 o'clock and 6o'clock will confirm a loose bearing. From experience, a failing bearing does not always mean that it is also loose enough to detect with this test.

Figure 9. Failed Front Wheel Bearing Outer Race

Now go out and get your elephant grease.