I’ve got a used older Sabbath September ti road bike. It’s knocking on a bit but I like it. When I got it it had a part Shimano 7800 Dura Ace group set. Over time I have acquired most of the missing bits (apart from front brifter which I’ve replaced with a similar looking 105 one). Anyway, last time I went out on it the free hub started slipping. On investigation in turns out that 7800 freehub was a complete one off and not compatible with any other. The rest of the wheels are in great nick, hubs silky smooth and recently rebuilt with new rims and spokes. So my choices to get the bike together again seem to be:
1. Scrap the wheels and get some newer 10 speed wheels of a decent quality (ultegra maybe).
2. Buy a new old stock 7800 rear hub that is for sale on eBay for £100 odd.
I am torn. I’d like to keep it original but am I just kicking the can down the road and be facing the same thing in another few years?
Waddaya think?

So a quick Google suggests the freehub has the part number Y3B990200 and it would appear these are no longer available.

I’m a big fan of the 7800 groupset so I’d keep it going, with a new wheel or hub. I can’t think of any other parts you’ll not be able to replace for a good few years.

Whether you get a new wheel or hub and swap the bits or indeed the whole hub depends on how much use the wheel has and how smooth the bearing runs are.

Think I’d just change the rear hub to one more commonly available, retaining the new rims. If you can get a Shimano one one with the same flange dimensions you won’t have the expense of new spokes.

Could you service the freehub or is it fubared?

The freehub is not a serviceable item (natch). The bike is pretty much my one indulgence so I am tempted to splash out the £100 plus on the hub just for the freehub. I suppose I could try flogging the hub on eBay after to recoup some of the cost. Here’s a pic of the bike on the last ride where the freehub started playing up. Note the fish.

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Looking quickly at some images of the freehub, it looks like unlike most Shimano freehubs, the pawls are accessible when the freehub is removed from the hub. Have you at least taken it off and given them a clean / oil?

Unfortunately the hub body without the obsolete freehub isn’t going to be worth much.

I suppose if the original freehub has lasted such a long time, it’s replacement should too, especially if you don’t use that nice bike in crappy weather too often. In the meantime you can keep an eye out for another spare for next time.

The freehub is not a serviceable item (natch)

According to Shimano almost none of their freehubs are…. But once upon a time there was an official Shimano tool for taking them apart, and do you know what changed between the time they were serviceable and the time when they weren’t…?

Thats right, they stopped selling the tool.

The 7800 is an odd-ball though as it doesn’t use the traditional style Shimano freehub assembly, so the same kind of rebuild possibilities aren;t available there, but I’d still start with the question why the freehub started slipping?

Is it because something is worn? drive ring? (which is in the hubshell), pawls? bearings and thus allowing movement so pawls slip? spring not returning due to lost tension or sticky grease, or debris etc.

It might be something you can fix rather than replace, or it might be a genuinely goosed freehub, or it could be the damage is actually in the hubshell itself.

I’d go for the NOS hub. Re-use spokes, fit straight back in the frame etc, etc.

How long has the original lasted?

Or as toby said, can you get the freehub apart and clean/lubricate? Keep as a spare.

Worth a try…I’ve rehabbed several freehub bodies this way.

https://www.youtube.com/watch?v=iQ6XgztsfmU

If I get the NOS hub (which I am erring towards now) I will just take the freehub off it as the present hub is fine. Once I’ve done that I can have a go at trying to get the old one going again as backup.

Did you get that from rich by any chance a few of the bits make it look remarkably like my old one, if so I built those wheels. The original ones obviously 😉

Assuming I’m looking at the right thing, the trouble with that is that with half the freehub being in the hub (Like a Hope / Campag hub):

Means that if it’s actually the track in the hub that’s worn, putting a new freehub body with fresh pawls in there may not help.

Pop the freehub off and visual examination first?

Reet, I’ve bought one. Will arrive from Spain in a week or so. Fingers crossed.

Yes Firestarter it’s your old bike.

Lovely looking bike mate. Worth the cost to get her back on the road.

Oh, thank you. I do enjoy riding it.

Update.
I finally got my finger out and took the old freehub off. It was in a bit of a state.

The new one however is a thing of beauty.

Still in the process of giving the cassette a complete degrease and clean up before reassembly.

Nice. Having just bought a beautiful set of 7700 10 speed wheels for £150 off the bay, I’d have said go there. Now look for a matching shifter!