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Rebuilding the Shimano Nexus 4-speed Coaster-Brake Hub
This is a translation of
Shimano instructions in German German flag
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by John "Demontage und Montage" Allen
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Shimano Nexus 4-speed hub

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About these instructions

This article translates the Shimano INTER-4 coaster-brake hub gear (SG-4C35) overhaul manual from German -- the only language in which we could find it on the Internet. Added editorial comments for clarity are in red. I thank Patricia Morris for preparing a draft translation, adding comments and locating the German manual. I've reviewed and edited her translation, and revised it to cover the coaster-brake version.

This site has another page with general information about Nexus 4-speed hubs, also linking to rebuilding instructions for the freewheel/Rollerbrake version.

The numbers of the steps below match those of the German version, which includes images illustrating each step. Added editorial comments for clarity are in red. Have this version and the illustrated German version on hand when working on the hub.

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Disassembly of the INTER-4 coaster brake hub


Disassembly steps

  1. Clamp the hub axle with the flat sides (drive side) in a vise.

    Note:  The threads of the hub axle must not be damaged.

  2. Remove the locknut and adjusting nut from the hub axle.
  3. Remove the brake arm and bearing retainer B from the axle.
  4. Remove the (large black plastic) dustcap (on the drive side) using a flat-blade screwdriver, then pull the hub housing upwards and off.

    The complete gear unit can now be replaced (if desired).

  5. Remove the brake shoe assembly.
  6. Use a screwdriver to remove the 9.0mm circlip (be careful not to lose it as it flies off).
  7. Remove the roller (brake actuator) assembly.
  8. Use a screwdriver to remove the 9.6 mm circlip (be careful not to lose it as it flies off).
  9. Slide the return spring unit along the groove in the hub axle upward and remove.

    Note:  Do not dismantle spring unit. This can make it malfunction.

  10. Turn the (gear changer) sleeve clockwise until it stops and pull upward from the axle. If it does not remove easily, turn the ring gear clockwise.
  11. Turn the planet carrier and ring gear clockwise and remove them.
  12. Using a (small) screwdriver, remove the (large, wavy) ring-gear circlip.
  13. Remove the  ring gear. 
  14. Using a screwdriver, remove  circlip C (retaining the 3 sun gears).
  15. Lift out sun gear 3 and sun gear 2. (If you also remove sun gear 1 for overhaul, the timing of the compound planet gears will be lost. See note on our main Nexus 4-speed page  for simple retiming.  The compound planets can be easily removed at this stage for overhaul by removing the circlip on the bottom - sprocket side -and tapping the assembly sharply to drop out the 3 planet pinions.  Remove sprocket first.)

The bearing retainer is secured to the axle of the coaster-brake version of this hub by a clip which is not designed to be removed.

The dismantling of the INTER-4 hub is now complete.

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Assembly of the INTER-4 coaster brake hub

  1. Clamp the hub axle with the flat sides on the drive side in a vise. (A bearing retainer and a clip are already installed on the axle of the hub.)

    Notes: Don’t damage the axle threads. The bearing retainer must be lubricated with plenty of hub grease.

  2. Install sun gear 2, gently aligning the teeth with the planet gears. (If sun gear 1 has been removed, retime the compound planet gears on installing - divot on tooth base of each planet gear must face radially outwards from the axle as described on the main Nexus 4-speed hub page.)

    Note: The teeth of the planet gears and sun gear 2 must be lubricated with plenty of hub grease.

  3. Install sun gear 3, gently aligning the teeth with those of the planet gears.

    Note: The teeth of the planet gears and sun gear 3 must be lubricated with plenty of hub grease.

  4. Insert the (sun gear retaining) circlip in the groove in the planet cage using a screwdriver.
  5. Insert the ring gear (washer is not used on coaster version) in the planet cage assembly.  (If the compound planet gears have not been timed in step 3, it is almost impossible to mesh the gear ring smoothly with the 3rd gear planets.)

    Note: The internal teeth of the ring gear must face downward and must be lubricated with plenty of hub grease.

  6. With a screwdriver, install the (large, wavy) ring-gear circlip in the groove in the planet cage.
  7. Install the planet cage assembly on the axle, sprocket side down, while turning it clockwise.

    Note: install with light force to avoid damaging the pawls, which would cause malfunctioning.

  8. Install the gear shifter sleeve on the axle, long-blades end down, while turning the ring gear clockwise.

    Test: After installing the sleeve, turn it lightly and observe that the shifter ring (outside the sprocket) turns along with it.

  9. Turn the gear shifter sleeve counterclockwise on the axle until it stops. With the tabbed face of the return spring assembly upward (tabs at the sides face downward), align the two lugs on the inside of the return spring unit and the two grooves in the axle with each other, and then side the return spring assembly  onto the axle. If installation is difficult, turn the tabbed sprung washer (top) of the return spring assembly counterclockwise while pressing the assembly down onto the shifter sleeve.

    Note: Lubricate the spring unit with plenty of hub grease.
    Check: When the spring assembly is installed, the axle groove for the retaining circlip must be visible.

    Reader Elmer, from the Netherlands, adds the following comments for the freewheel version of this hub, but this step of the instructions is the same for the coaster-brake version:

    During assembly I experienced 1 problem with step 10 and wanted to let you know how I solved it.

    I couldn't get the return spring unit into place, so I followed the instruction above (turn the top washer counterclockwise). Unfortunately this caused disassembly of the unit itself. So you have to be very careful. I have managed to assemble the spring unit back together. First assemble it without any tension on the spring (there is only 1 way to connect the 2 washers with the spring in between). This way you know how the 2 washers connect. Then I used 2 pliers: 1 to hold 1 washer and the other to turn the other washer counterclockwise (in total 360 degrees). Actually you have to turn a little bit further, press the washers towards each other and then release it. If you do this right, the 2 washers will be connected again. This is somewhat delicate as to much movement will free the spring.

    To get the spring unit in place, I kind of wiggled it into position instead of really turning it counterclockwise. And yes, it works again.

  10. Install the 9.6 mm circlip in its groove in the axle. This is the slightly larger of two circlips. Using the mouth of a 19mm open-ended wrench is a good way to push the circlip into its groove without distorting or losing it.
  11. Install the roller assembly (roller side up) so that it engages the lugs in the planet cage.
  12. Install the 9 mm circlip in the groove in the axle.
  13. Install the brake shoe assembly so that the drag spring in the roller assembly engages one of its two slots.

    Note: The inside and outside of the brake shoe assembly must be lubricated with plenty of hub grease.

  14. Lower the hub shell over the gear assembly, turning it gently counterclockwise to seat it.
  15. Reinstall the (large black plastic) dust cover A on (the drive side of) the hub housing.
    • The inside of the dust cover A must be lightly lubricated with hub grease in order to prevent the intrusion of water.
    • Press the dust cover A firmly onto the hub housing until it locks audibly into place.
    • Check: After installing the dust cover on the hub shell, test whether the shell can easily rotate counterclockwise.
  16. Install bearing retainer B in the hub shell.

    Note: The bearing retainer must be installed with the ball side down, flat side up. Use plenty of grease.

  17. Install the brake arm assembly on the axle and rotate it left and right so it engages the brake shoe assembly; then push down the brake arm assembly all the way.
  18. Adjust the axle nut for easy rotation with minimal play and secure it with the left cone locknut.

The assembly of the INTER-4 hub is now complete.

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Translation and notes copyright © 2015 Patricia Morris, John Allen

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