Shimano 105 freehub FH-5800 - pawls not engaging, repair or replace?

Question

After a thorough clean and (over) oiling with WD40, my Shimano 105 FH-5800 freehub stopped engaging. Sounds like a common fail: I had previously thought that more oil = better. Live and learn!

Bike is just over 10 years old but in good condition otherwise. I don't know if:

1. This can be dismantled, cleaned out, re-greased and put back
2. If the bit with the pawls in it can be replaced?
3. Or if the whole freehub should be replaced and wheel rebuilt around it?
4. Any other options?

I've looked at countless guides online to do with all three, but I just can't work out what applies to me and my kit and what doesn't.

I'm also not sure what I'd attempt myself and what I'd need a shop for. I certainly wouldn't attempt (3), but would considering (1) and (2) with solid advice. I would need to buy the Shimano tool and a chain whip first though - until this happened I'd never heard of freehub, cassette, pawl or Sheldon Brown for that matter - I'm getting a good education here!

Here's the back wheel when going wrong: https://photos.app.goo.gl/8p3vnYAyxyndNtoz5

https://photos.app.goo.gl/CYjnuzZFZSuhisDM6

(apologies for the poor backing track 🤣)

Update: https://photos.app.goo.gl/oBSpGwfBUpxfyxDJA (additional photo of hub model)

Happy to send more images, but as far as I'm aware, unless I get the tools I can't currently get the cassette off to see more.

Thanks all

Answer 1

It should be possible to do one of 1. or 2. but the way Shimano hubs are, the pawls are contained in the freehub body, which is pictured below.

So that means option 2. is that bit more achievable than option 1 (but costs more in parts). You'd take the cassette off with tool and chainwhip, then disassemble the cup and cone hub using a cone spanner and regular 17mm, before the freehub body is removed with a big Allen key. You could always investigate inside the freehub body first and see if it just needs degunking. I doubt that WD40 penetrates all the way inside, it might just need it's overdue 10-year clean (jks that's not a thing).

Here is an image of a random Shimano rear hub exploded diagram, that I stole off of eBay. Part number 15 is a large bolt that you have to access to remove the freehub (Part Y3BL03000 for many hubs incl FH5800). I believe from Q&A on a retailer's website that it is a 10mm hex.

Doing 3. is a possibility, don't be afraid of giving it a go, but that might be 'running' whereas option 2. is 'walking'. Arguably.

Option 4. is buying a new wheel. Doesn't have to be that expensive, but would be more costly than option 2 and less fun.

Your next questions might include:

"how do I turn the 10mm Allen key with force now the long end is in the hub?" (Use a spanner)

"help, I took apart my hub and can't get it back together!" (see diagram, see How do I reassemble this Quando rear hub?)

and, "something, something, Darkside" (see a counsellor).

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You should check the rim wear and overall health of the wheel before spending any money on spare parts, or even tools. If the rim is old and worn down near its limits then replacement parts wouldn't be the most economical way to go, you could put that money towards a new wheel. Tools are fun and useful going forwards though.

Answer 2

WD40 is a water displacement product, not a lubricant and not oil. It actually dries to a sticky mess. I know mechanics who use it to put on MTB grips, because they slide on while it is wet, then when it dries to become tacky, it holds the grips on nicely.

It is highly likely that you have a mess of WD40 inside your freehub preventing it from engaging. If you do not have tools to disassemble, you may try soaking your freehub in some sort of solvent, then relubricating with actual oil (this will lead to other issues down the road). Freehubs are generally packed with some sort of grease that is intended to lubricate and prevent moisture intrusion. If you contaminated it with pressurized WD40, you'll need to find a way to clean that mess out. Ideally you will clean out the contaminated grease and lubricate it with new appropriate grease.

Unless you are running a very cheap wheel, I am guessing it would be least expensive to find a shop that will repack your freehub with appropriate grease. Shimano's freehubs are not meant to be disassembled and repacked. However, many cyclists that ride in colder tempeatures (like folks racing fat bikes in January) do take apart their freehubs to winterize them with winter weight grease. You might be able to find such a mechanic with some searching.

Answer 3

The few times this has happened to me, it was because 2 of the 3 pawls were cracked and the last one was sticky, which is normal but not noticeable unless there’s only one. They’re not that hard to replace if you can get spares and grease.