deux jambes

EDIT: Oops... Sorry for the misplaced post. Thought I was posting from the main C&V page. And for some reason I don’t have the option to delete this post from the edit feature.

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I made a decision to swap the hub bodies out between a 6400 UG and a 6401 HG.

When researching the procedure I learned that I’d need an unobtainable Shimano freehub disassembly tool. And I also learned that a tool can be fabricated from an 11/16” socket as well as a Park Tool FR-8. In both tutorials, the DIY tool was made with two tabs as if the 6400 series bearing cups only have two notches. Well, I found that each of the cups I have use 4 notches for installing/removing.

Also, in one YouTube tutorial, R.J. The Bike Guy gives instructions to swap the cones (not just the bodies) as part of the conversion. I’m not sure why though, because unless I’m just not seeing it, there doesn’t appear to be any difference between the cones.

HG on the left, UG in the right:

jeirvine 

Interesting. Only swapping I've done is 7 speed to 8 speed complete freehub bodies, (which is dead simple - only a 10m hex needed). Are UG and HG freehub bodies not swappable?

deux jambes

Interesting indeed.

At the 1 minute and 37 seconds into the video, R.J. begins to explain that the bodies are not swappable as complete units.


But now that you’ve raised the question, I checked both lower race and pawl assemblies. I’m not seeing any difference between the two.

Assembly on the left is from the 6401 HG, and the assembly on the right is from the 6400 UG:






Additionally, they both fit and seat on the 6400 hub shell below which doesn’t appear any different than the 6401:





Both hubs used in this project btw were originally 7 speed hubs.

At this point, I’m wondering if I’ve unnecessarily disassembled two complete hubs.

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EDIT: Calipers are showing that the race/pawl assembly from the UG is 0.10 mm longer than it’s HG counter part. And a 0.60 mm difference between cups. The HG being the larger of the two.

jeirvine 

I think he's right in some instances, but Shimano made a lot of different hubs. Looks like the 6400 series is swappable. And all my swaps were either tricolor or 105, so maybe they are more interchangeable than other lines.

deux jambes

Seems that way. If I ever find a reason to make the same swap using the same series in the future, I’ll try plug n play first.

Pompiere

I didn't know they were not interchangeable, I guess I'll have to swap mine back. I swapped a 7 speed UG with a 7 speed HG from a spare mountain bike hub with no issues. The first one I tried was not going to work, but it wasn't a Shimano unit.

Edit: To clarify, I swapped the whole free-hub, not just the shell.

cb400

I can confirm that the early UG hub race (not attached by an allen bolt) only has two prongs. Maybe having 4 prongs is a good indicator of being able to swap easily?

cb400bill

Thread moved from C&V Sales to C&V.

deux jambes

Thanks for the confirmation.

Maybe that’s it. Both hub bodies for this project required a 10 mm allen wrench for removal. Taking that into account with the fact that they both take a 4 prong tool, might help explain things a bit.

Well shoot. Might have been an unnecessary job s as after all. At least it’s a bit of gained experience, and a fully serviced hub in the end.

dddd

Taking the freehub bodies apart is not the way to swap UG-6 to HG-7.

This is not to say that all of these modular (attached with hollow bolt) freehub bodies can be swapped to different hub shells, as different hubs from different level gruppos often will not swap without the cogs then being either too close of too far from the hub flange, AND with the hub's overall "axle width" changing by a couple of millimeters.
I've had failures trying to swap bodies between different MTB gruppos and between different road gruppos, but I have swapped between different 64xx hubs with no issues (UG6 to HG7 conversion).

Different freehub bodies also have dedicated axle cone hardware in terms of how the sealing surfaces of the cone and body line up, so I always try to keep the freehub body and drive-side bearing, seal, washer and locknut intact as a set when swapping freehub bodies.

Two prongs on a carefully carved 13/16" socket will handle the torque needed for removing the locking cup/cone piece. Crafting a 4-prong tool with all four prongs clocked at 90-degrees from one another is going to be very difficult to virtually impossible for the home craftsman!

Editing: One more reason not to try swapping the freehub body outer shells is that each assembly gets selection-fit shimmed at the factory to arrive at correct freehub body bearing adjustment tension.
Reassembling after swapping parts will likely require some combination of shim thicknesses that isn't part of the original pair of bodies.
One CAN shorten the freehub-body cone on the back side of the axle-bearing cup, using wet-or-dry paper. But such "machining" is irreversible and if the assembly turns out to be adjusted tightly after such modification you might end up with one or more unusable bodies.