Special hub grease?

[confusedcyclist]

The dealer manual for my Deore XT FH-M8110 rear hub is calling for Special grease (Seal Grease for Freehub) and Premium Grease. I sometimes appreciate proprietary consumables are unavoidable, like with hydraulic fluid, but I don't normally buy into this with grease, as it's usually just a way to sell own brand consumables.

The manual specifically states use with other types of grease, or mixing of grease 'may' cause malfunction of the freehub. Just for context, I am trying to undo a malfunction caused by the shop that I bought my bike from. They re-greased it under warranty when the hub started creaking after a few hundred miles of fair weather riding. When I got the bike back, I noticed the creaking had been solved, but now the freehub must have some resistance as the cranks and chain spin without my pedalling them when coasting, and occasionally there is a horrid grinding sound coming from the hub. I suspect it is the freewheel, but can't say so categorically, I have tried to loosen the locking nuts so there is a touch of play in the hub as I understand is ideal, it seemed a little too tight by my own experience, but the issue persists. I suspect the freehub has been packed with too much grease, but could it be the shop used the wrong kind of grease?

Shimano would say use their premium and special seal grease, because it helps them sell two of their propriety tubs. Does anyone who works in a shop buy into the dealer manual advice? I'm thinking of degreasing and cleaning the freehub, before giving up on the hub entirely and replacing it, so just wanted to hear from some experienced folk on these types of grease. I imagine the premium grease is interchangeable with other brands, but how about the seal grease? Can anyone recommend an alternative to shimano's seal grease?

 

[MichaelW2]

Seal grease is for the freewheel part of the hub and is probably thinner than the usual wheel bearing grease so the pawls dont stick.
There are various viscosity rating systems. NLGI is one and normal grease is "2" but pawl grease is supposed to be 0 or 1.

 

[Ajax Bay]

@figbat

 

[figbat]

I’d go with what @MichaelW2 said regarding consistency; an over-thick grease will cause drag. If it were me I would research the proprietary greases to see what they look like, then find something off-the-shelf to match. I doubt they’re anything particularly special, they will just be of a specific type.

 

[confusedcyclist]

I managed to get a chance to disassemble the hub tonight, and not just fiddle with the hub nuts, I was hoping before any seal grease arrived, I could clean it up and inspect for damage... and I was not surprised to see green grease all over the freehub body, even on the seal with an engraving that clearly states 'don't lubricate inside, do not dissemble' .

As per the dealer manual, grease getting into the freehub body will lead to malfunction, and this one has well and truly failed now. The image here is after extensive wiping down, trust me, grease was everywhere! Its tricky to see here clearly, but that silver ring is supposed to be symmetrical but has warped, the silver tab on one side is flush with the free hub body, and on this side it is elevated above the ratchet, this must be what was causing the grinding sound as the hub spun, interfering with the ratchet mechanism. I'm not sure how much this is to do with greasing the hub, or just a shoddy job by the mechanic as they reassembled it after it went in for misdiagnosed creaking (I thought it was the motor!) but rather than fart around with the mechanic and entrust them with my bike again I thought I would order a replacement freehub, but there are non in stock anywhere! Instead, I have ordered an entire new hub, I found a 28 spoke model on sale (still not that cheap) but less hassle than another trip to the shop. I can strip the free hub off, and save the rest of the hub internal parts (spare bearings, springs, seals and an axel) for another rainy day. Pity that I had to faff with this, this shop won't be getting any more of my business, as one way or another, this hub left their shop totally FUBAR.