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Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 4:04 pm
by DonW
Hi,
One of my winter projects is to rebuild various spares. I have 3 transmissions apart on my bench. A few of the bearings are very obviously bad, but most feel smooth. Last time I did this (4-5 years ago) I bought bearings from Ed Korn (now retired but his business is still operated by another fellow) and had a choice between European(FAG or SKF) or Japanese bearings. Can't even remember what I chose..
Anyway, I'd appreciate suggestions on what kind of replacements, and how to determine if a bearing needs replacement at all. Suggested sources? I know I can buy from the local bearing house...
thanks,
Don
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 4:45 pm
by Kurt in S.A.
Check out Anton's page on transmissions; at the bottom is a list of bearings:
http://www.largiader.com/tech/airtrans/
If there's doubt on a bearing, then there is no doubt! Personnaly, I'd just replace them.
Kurt in S.A.
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 4:53 pm
by Garnet
http://www.bmwhucky.com/010023.html and Motobins have bearing kits.
You may be able to put together a less costly set from a bearing supply house.
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 5:31 pm
by Major Softie
The scarier thing to me is the fact that there now seem to be many counterfeit bearings out there, and you can end up with something that appears to be genuine, and can actually be a very low quality Chinese, or worse, knock-off, but it's labeled and boxed as the genuine article.
I have no idea how you make certain you are avoiding that problem. I would hope that, for instance, if you dealt directly with Timken, you would be certain you were getting real Timkens, but I don't know how the wholesaling system is set up, so I don't even know if that would make it a certainty.
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 6:14 pm
by dwire
garnet wrote:You may be able to put together a less costly set from a bearing supply house.
+1 on that notion, but M. Softie makes a very good point...
Major Softie wrote:The scarier thing to me is the fact that there now seem to be many counterfeit bearings out there, and you can end up with something that appears to be genuine, and can actually be a very low quality Chinese, or worse, knock-off, but it's labeled and boxed as the genuine article.
I have no idea how you make certain you are avoiding that problem. I would hope that, for instance, if you dealt directly with Timken, you would be certain you were getting real Timkens, but I don't know how the wholesaling system is set up, so I don't even know if that would make it a certainty.
I may be able to ask a few dist. that might know providing they are still around and in business. It is my understanding from others that in fact, that for which you speak has gotten nearly as bad as the prescription drug counterfeits out there. This is a sad thing. I'll report back if I can get some good concrete answers on supply routes and the like. (Besides, I'll be purchasing a gaggle of them over the winter myself anyway.)
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 6:27 pm
by Max Headroom
There's not lot of difference in quality between the major brands, in spite of what their advertising may try to suggest. Any reputable brand is going to give good service and will conform to ISO specs for dimensional integrity and load capacity.
Having said that, I have a personal preference for the SKF brand but will happily use FAG, NSK, Nachi, or NTN.
The biggest headache with airhead 'boxes is the front output bearing which is a 6403 C3. This bearing is usually the first to fail, and the failure usually takes the form of the steel cage fracturing which allows the balls to gather in a bunch as well as bits of broken cage floating around the gears, creating the growling noises which we know will herald a fresh assault on our time and funds. Unfortunately there is no direct replacement which would give better service, and even extensive searching through catalogues hasn't revealed any alternatives which could comfortably fit without modifications. In most cases those modifications could allow compromises which could be worse than the original steel cage 6403 C3. Six years ago I was lucky to find a NOS 6403 with a brass cage which I fitted to the 'box I built up for my R90S. Very, very rare bearing.
My preference is for plastic, phenolic or brass cages for gearbox applications. A standard steel cage bearing is not as ideal as it doesn't cope as well with the variable loads and vibrations inherent with automotive/motorcycle gearboxes. Steel cage bearings are often fitted as a cost compromise, although some manufacturers have specially reinforced steel cage bearings for made specifically for automotive applications. SKF does a 6304 C3 with a reinforced plastic cage, and so does FAG which I'd consider to be better than a steel cage. As an aside, I have replaced the front cluster bearing in several 'boxes with an NJ304 C3 cylindrical roller bearing (same as the front input bearing) which has double the load capacity of a 6304 C3 and also make the 'box easier to assemble.
The front input shaft bearing is now getting expensive. There is an alternative which is just as capable as the original, and also allows a standard 25 x 40mm front seal to be used instead of the factory 26.5 x 40mm seal. I can give you details if you're interested. I used an aftermarket Viton front seal as it copes with the heat better than nitrile does. Nitrile is the seal material most bearing houses sell, and it's designed to work to a 120C limit. Regular exposure to that limit shortens the seal's lifespan, while Viton is good to 180C.
Just as well I'm not getting charged by the word . . . .

Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 6:45 pm
by Ken in Oklahoma
Good stuff Max. I've save a copy to my computer for future reference.
Not too many words for me!
Ken
Re: Types and sources for tranny bearings
Posted: Fri Dec 03, 2010 6:47 pm
by dwire
Good info Max, I can say the fake bearings shipped to a facility I worked at a few years back DID NOT conform to ISO specs. (I'd think by how quickly they trashed the equipment they were used in, they were made to POS specs...) If they would not have closed the facility, their was to be a giant lawsuit over the issue. Besides, if the fake garbage conformed to spec, we wouldn't care who made the forgeries; all any of us want is a product that is as described and meets or exceeds its ratings. --> Oh and as cheap as we can get them; hence why there are knock-offs.
Wish I knew more, but I was not the tradesman involved, I simply got to see a couple multimillion dollar issues over the deal and was present for all the bitching once they "figured it out." Buyer Beware.

Re: Types and sources for tranny bearings
Posted: Sun Dec 05, 2010 12:32 pm
by DonW
The front input shaft bearing is now getting expensive. There is an alternative which is just as capable as the original, and also allows a standard 25 x 40mm front seal to be used instead of the factory 26.5 x 40mm seal. I can give you details if you're interested. I used an aftermarket Viton front seal as it copes with the heat better than nitrile does. Nitrile is the seal material most bearing houses sell, and it's designed to work to a 120C limit. Regular exposure to that limit shortens the seal's lifespan, while Viton is good to 180C.
I'm interested... Also interested in the source for Viton seals
thanks,
don
Re: Types and sources for tranny bearings
Posted: Sun Dec 05, 2010 4:35 pm
by Frog
I buy full sets from Hans at Hucky's BMW. He supplies SKF. I have purchased a set from a local bearing house and it ended up costing more than what Hucky's charges. I think the Hucky set $155, while the local bearing house was about $180.