How to Grease a U-Joint with Flush-Type Fittings


All vehicles have lubrication points in their suspension and drive line components that call for a special grease. Without grease the components can't rotate, twist or swivel easily in their seats or on their joints. Several grease fitting designs exist for different applications. The most common is the "zerk" fitting, which has an interior ball and check valve that allows grease to enter but not exit. The flush-mount fitting has a valve that must be lubricated with a needle-nose grease gun adapter. You will have to obtain the correct size adapter fitting for a standard hand-pump grease gun when lubricating a U-joint with a flush-mount fitting.

Things You'll Need

  • Floor jack
  • Jack stands
  • Shop light
  • Safety glasses
  • Carburetor cleaner
  • Cup
  • Toothbrush
  • Rags
  • End wrenches
  • Hand-pump grease gun
  • Needle-nose grease gun adapter
  • Place the gear shifter in park or neutral, according to your transmission type. Leave the emergency brake disengaged. Place a floor jack under the rear part of the vehicle and lift it high enough to place two jack stands under the frame near the rear wheels. Raise the front of the vehicle with the floor jack and place two jack stands under the front frame near the wheels. Extend the jack stands to maximum height.

  • Hook a shop light to the chassis under the vehicle so you can clearly see the front and rear drive line U-joints. Locate the flush-mount grease fitting on the front U-joint cross-shaft. If you can't see it, you must place the vehicle in neutral and rotate the drive line until the fitting shows at the bottom of the U-joint. Place the gear shifter in park and set the emergency brake.

  • Don safety glasses. Dip a toothbrush in a cup of carburetor cleaner and clean the U-joint and fitting. Do the same with the rear U-joint, remembering to free up the transmission and turn the drive line to locate it. Wipe both U-joints dry with a rag.

  • Remove the end fitting nozzle on a standard hand-pump grease gun with an end wrench. Screw on a 1/4 x 28 standard size needle-nose grease gun adapter and tighten it with an end wrench. Make sure you have a grease gun cartridge in the gun cradle. Lie on your back and lay the grease gun tube across your belly. With one hand, shove the needle-nose adapter up into the fitting hard, keeping upward pressure.

  • Pump the grease gun lever with the other hand three to five times until grease exits the bottom of the grease cups on the U-joint. Remove the adapter fitting. If no grease exited the grease cups, shove the adapter up harder into the flush-mount fitting and pump again. Perform the same operation on the rear U-joint, making sure you push up into the flush-mount grease fitting. Rotate the drive line as needed for access. Wipe excess grease off both U-joints.

  • Raise the vehicle with the floor jack and remove the jack stands. Test drive.

Tips & Warnings

  • If you need to lubricate the flush-mount fittings on a very large truck, you must use the needle-nose grease gun adapter that comes in the larger, non-standard size.

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