Diamond drive bearing upgrade thread with lots of pictures

[Paul2727]

Great thread. People should know that if you are not removing the entire case from the sled, you still most likely will have to loosen the bolt from the brake side to compensate for the extra width of the bearing. Once the case-cover is back on, just torque the bolt back to spec!

The problem described by Rucky is more common on the 2010 and 2011 Artic M8's, and does occur on a few 2009 M8's. It has to do with production tolerances on the aluminum tunnel assembly and the drive components from the DD housing and cover, to the brake assembly on the right side of the machine. The problem with some M8's is the tolerances "stack up" in such a way, that the drive shaft components are longer than the tunnel, DD housing, and brake housing components that hold the gear shafts, drive shaft, and track shaft assembly. Think of it as three shafts stacked end-to-end (from the left side: the DD reduction gear with the "bad" bearing, then the planetary basket with the DD output drive shaft, and then the track shaft). Those three shafts stack end-to-end. There should be some axial clearance (from 0.010" to 0.030") in the entire DD gear / drive shaft / track shaft drive assembly. They are splined or geared shaft connections, so it works fine with some clearance, allowing every bearing to find it's center.

If you happen to have DD & brake housings and a tunnel that are on the short side of the Arctic manufacturing tolerances, and your three shafts are on the long side - you are an unlucky owner and the combined shafts are too long to fit in your housings / tunnel. If you have no axial clearance with the stock 6203 bearing or with the new, stronger, slightly wider 5203 bearing, the aluminum tunnel will flex and put thrust loads on all the bearings. None of the bearings are intended for thrust loads, and the original 6203 bearing was the weak link in the chain, so it gave out first. Studied several forums on this topic and if you have no clearance, most people recommend shortening the track shaft slightly (from 0.020" to 0.160") on the DD end, to provide some axial clearance. Again this is needed on most 2010 and 2011 Artic M8's, and on a few 2009 M8's. Nobody can tell you exactly what to do, because all machines are different due to the (poorly managed) manufacturing tolerances.

 

[Paul2727]

So should I buy the BDX complete kit, the BDX 5203 bearing by itself or just the 5203 bearing from a local bearing shop where its probably cheaper? There are two 5203 bearings listed as well, a 5203-2RS which is a sealed bearing (looks like the BDX bearing) or a 5203-ZZ which is a shielded bearing, which one is best? The sealed one has grease in it, but wouldn't you want the DD oil to get into the bearing instead? It says you can remove one of the seals or shields and that would allow oil into it, but which side of the bearing should you remove the shield from? Thanks.

Bearings with lithium base or polyurea base factory grease and metal shields (non-contact seals) or rubber contacting seals are designed for slow speed applications, and for dirt / crap exposure on the outside. Bearings running with grease at high speed (above 2000 rpm) will run hot due to churning through packed, heavy, vicous grease. The 6203 / 5203 bearing in the DD runs up to 6000 rpm. For high-speed applications, all bearing makers recommend oil mist lubrication, not grease. I suspect that is why many owners have noticed damaged cages, blown bearing seals, and dark DD oil (from overheated rubber and overheated grease contamination - above 250 F). In any case, the grease will contaminate the properties of your DD gear oil, and the bearing seals will not allow microscopic crap to be flushed from the 5203 bearing during your annual oil changes. We don't need seals in the Diamond Drive because the 5203 bearing is operating in a clean, internal gearbox environment, full of oil mist. Synthetic gearbox oil is the same or better than any oil contained in any grease.

Another issue: the BDX supplied 5203 2RS bearing (the 2RS means rubber seals) is an inexpensive Chinese / Taiwan bearing (many are available on ebay for about $12). I prefer SKF (Sweden), FAG (Germany), or NTN (Japan) bearings. In my 2009 M8 I'm using a SKF 5203 ATN9/C3 bearing. The SKF 5203 ATN9 might also work. Don't use the SKF 5203 ATN9/C2 - it has internal clearances that are too tight (from 1 to 12 micron) for the press fit onto the DD shaft, which "stretches" the inner race slightly. The 5203 ATN9 has normal internal clearances (from 6 to 23 micron, before stretching onto the DD shaft) which may work, and the 5203 ATN9/C3 has slightly larger internal clearances (from 13 to 31 micron). A good oil film will be between 1 micron (hot) and 3 micron (cold) on a total of 4 surfaces (top & bottom surfaces of the balls, both above and below the shaft). All remaining lubrication will be plowed away, creating heat. That's why I think the C3 bearing is the best fit. Minimum 13 microns internal clearance, less roughly 7 microns for the press fit, less 4 microns for the four oil films. You need some internal bearing clearance, or the bearing will run hot due to the friction from metal-to-metal contact, which will greatly shorten the life of the bearing.

The "ATN9" suffix refers to a glass-fibre-reinforced-polyamide plastic cage, which has the lowest lubricated friction and is almost as strong as a pressed-steel cage. For high acceleration, high speed, and high vibration applications like in the DD, the only cage that is better is machined brass, which is very rare, and only comes in some sealed 3203 bearings, and not in the /C3 dimensions.

The SKF 5203 has been recently replaced by the SKF 3203 "Explorer" bearing series, which is a slightly higher quality bearing, with slightly higher load capacity, and slightly longer life. Both the 5203 and 3203 bearings are available on ebay. Make sure the bearing you buy is new, clean, plastic wrapped, and in an SKF box. Don't buy dirty, old, loose bearings. The 5203 and 3203 have the exact same outside dimensions: 17 ID x 40 OD x 17.5 Wide in mm. Both are about $35 on ebay. Look for the ATN9/C3 following numbers. For more info, a very detailed SKF catelog: http://www.skf.com/files/151315.pdf

With Chinese and Taiwan bearings, you will never know what they have for steel quality, dimensional quality control, or internal clearances. You get what you pay for. Good luck!

 

[suavegato]

Pardon my "ignance" but does this bearing issue concern the 09 M1000 to or just the M8's? I have one of each and would want to do them both at the same time if needed.
Thanks.

 

[kentz]

Hey Paul27 thanks for the in depth response. Unfortunately I already ordered one off of the internet from the states based on a link in this thread. Looking back it is probably a piece of crap since it was $8, it looks identical to the BDX one that they are charging $15 for so I figured it was the same. I called a couple local bearing shops here in Edmonton and they were all priced at around $50 and no one seemed to have the 5203 ATN9/C2. I called SKF as well and they wouldn't sell me one since they only sell to companies and won't sell to the public off the street. So I guess I will wait to see what comes from the states and go from there. Hopefully there will be a manufacturer on the bearing so I can tell if it is junk or not. When I talked to BDX they said it was a sealed bearing that they were selling as well. I asked if it would contaminate the DD if the seal leaked and they said no big deal it will just lubricate the bearing. It doesn't make sense to use a sealed bearing in a gearbox with oil unless the oil level doesn't reach that bearing but this bearing is in the bottom of the case is it not? and should be well lubed.

 

[Stg2Suby]

Paul27 - thank you kindly that's the best explanation I've seen so far on the clearance issue.

Kentz - I got my 3203 from Commercial Solutions in Edmonton it was $30 and made by INA which I think is same company as FAG. It's a 2RS bearing but after reading Paul27 comments I would have ordered a non-sealed bearing in retrospect.

 

[killerrf]

i wouldnt worry about the seal thing. just put the new bearing in and run with it. or if your worried about the seal thing just take a small screw driver and pop the seals out. i would install the bearing with the DD still in the sled. cause when you put the sled back together if your cover doesnt want to go on and stay on without popping out then i would grind down the shoulder on the shaft you putting the new bearing on.

 

[Paul2727]

If you go to an industrial power transmission store (like Bearings and Drives or Motion Industries) they can sell you whatever you need.

If you can choose the ultimate bearing, I recommend the SKF 3203 ATN9/C3 as a first choice. Saw one on ebay a few days ago, but it's gone now. If you can't find that, then the old stock SKF 5203 ATN9/C3 (copy attached) or the standard clearance SKF 3203 ATN9 will probably work fine. You can also use the SKF 3203 A2RS1TN9 and pop off the 2RS1 rubber seals. Other than the seals, the 3203 A2RS1TN9 is identical to the SKF 3203 ATN9.

The /C3 is specially designed with slightly larger internal clearances for heat-shink or press-fit applications, like we have in the DD. Pressing onto a shaft stretches the inner race a few tenths of one thousandth. People have said the bearing press fit is fairly easy, so there may be minimal clearance reduction on the DD shaft, but I don't know for sure - I've not measured mine.

Definitely don't use the /C2 bearing - it has tighter than standard internal clearances, for unheated, non-interference fit applications like a precision machine shop spindle. In the DD we have both heat and an interference fit.

Forgot to mention earlier - this is a great forum - great pictures - very helpful - THANKS a bunch!

 

[kentz]

Thanks Paul27, once again your bearing knowledge boggles my mind. Do you work for a bearing company or are you a machinist or something? I think ill just take all the part numbers you've listed in your posts and take that info down to Commercial Solutions and see what they have in stock.

Thanks.

 

[gibsons]

thanks for the info paul27, but now i'm thinking i may have bought the wrong bearing. mine is an NSK 3203B-2RSRTNGC3.

 

[Paul2727]

Kentz: Thanks for your kind words, but I certainly don't know all there is to know about bearings - far from it. It is such a broad and complicated science, from farm implement applications to the space shuttle, and everything in between. I do know a few things because I teach industrial reliability and maintenance classes about bearings and lubrication. Yet there are so many things I don't know, especially super-high-tech stuff, like aerospace applications. Jet turbine bearings are way beyond my skill level.

Gibsons: Your NSK 3203B-2RSRTNGC3 bearing will probably work good for you. I know NSK is a very well respected Japanese bearing company. There are a lot of good Japanese bearing makers. Any brand bearing Yamaha, Honda or Suzuki use in their engines and transmissions will probably be very good, the best in the world, because those engines have the highest power density. Looks like your bearing has 2RS seals and a C3 fit. You can pop off the seals and flush the grease prior to assembly. Lithium grease isn't such a big deal for your DD synthetic gear oil, but Polyurea grease doesn't mix well with anything. And since Polyurea grease is the best grease for sealed bearings, that's likely what you have. I don't know as much about NSK brand, here's more info: http://www.nskamericas.com/cps/rde/xbcr/na_en/TNSK_CAT_E1102f_Rolling Bearings.pdf

Be sure to give your bearing a few drops of DD gear lube after you clean it, before you assemble your DD, for startup lube. Good luck!

 

[Paul2727]

Is this correct?

 

[Stg2Suby]

Yes that's what I was going to do was machine that shoulder down where your blue line is pointing.

 

[Paul2727]

My DD was a mess!! Shrapnel everywhere! Total bearing cage failure. Not sure about the cause, because the rest of the stock 6203 bearing is in great shape! Tight axial & radial clearance, spins very smooth. Don't know why the cage failed. Maybe a cheap Chinese JUNK bearing ?? Or from thrust loads ?? Who knows ??

My 2009 M8 has 600 easy miles. Repair details are attached. Fairly easy job. Good Luck!

Updated attachment on Jan 15, 2012.

 

[kentz]

Man is that a great step by step procedure, great work, thanks a lot Paul27!

 

[Paul2727]

Got the machine work done today. Updated the results in the pdf file posted above.

Good Luck! And lets pray for snow!

 

[Paul2727]

Can't edit my previous post. The 2009 M8 DD drain plugs are 12mm x 1.25mm thread pitch. NOT 12mm x 1.5mm as included in my PDF above. Sorry for the misinformation.

 

[Slamnek]

Thanks for the detailed report. I had my 09 done and was told that there was no need for machining and my cover went on perfect, no rocking and it didn't pop off. I am starting to think that i was mis-informed because i think my jackshaft bearing is pooched so i will be pulling it all apart again and post my findings.

 

[Camino]

I tore into my 08 M8 this week. 1200 miles on the dd. The 6203 bearing was starting to crater. Not sure the bigger bearing will work. The spacer is only about 1mm. From the pics the shaft looks longer because of the two extra gear rings for the mechanical reverse. Not sure if milling the shaft is prudent. I will probably put the 6203 back in to get rolling for this weekend. Hopefully purchase a better quality bearing from a bearing supplier. Anybody else tackle the mechanical reverse dd.

Love the detail in this thread. Thanks to everyone

 

[pteroducktel]

Hi!
If i dont want to grind the shaft, can i use 4203?
Thanks!

 

[Slamnek]

I completly forgot about this thread. I thought i had a jack shaft issue because i was hearing grinding noises and it turned out to be a bolt that rattled loose and slipped under the break disc causing some awesome sounds. No machining required on 09 and newer DD only the ones with mechanical reverse.