Final Drive Disassembly in Search of Wear

[kris]

1986 K100RT....68,XXX miles (just under 110,000 KM). Slight play in the rear wheel when rocking it at the 3 o'clock and 9 o'clock position (or 6 and 12, etc.) Pulled apart the drive. Make sure you heat the 2 tapered rotor retaining bolts to 260F (126C) and then hit the heads with either Freeze It spray or ice cubes to shrink the socket head back down. Hit with impact driver (hand held used in my case) to loosen then get on them with your ratchet right away. Factory used permanent Loctite on these bolts and you will surely strip the heads if you don't follow the above. Balance of the housing bolts (9, I believe) were cooperative save one. I used the heat and ice method to loosen it. Tap the housing gently with a plastic mallet and it should come away fairly easily. Be gentle. No metal hammers or excessive force. The tapered bearing actually came off by itself as I was wiping the unit down! That is when I noticed the spacer/ washer wear.


I had no noise or roughness in the FD. An online rebuild video (from a guy who does a lot of these) indicated it was almost always the large ball bearing that would fail. All looks new in my FD. Ball bearing rolls smoothly and seems tight. Taper bearing race is smooth and new-looking. I had no oil leaks. Seal looks good. I think, in my case, that it is my tapered roller bearing....the part I didn't order! There seems to be enough play in it to explain the sympton. NB - no metal bits, shavings, etc. anywhere in the FD unit. Nothing on the magnetic drain plug. Could just be that the tapered bearing has worn a bit.  The other strange thing is that the spacer/ washer beneath the tapered bearing showed signs of wear....odd.


Question - is it OK to replace the bearing but not the race? (it is a bugger to get out)


Question 2 - when replacing the large ball bearing one has to measure for shims to get the right preload on re-installation. Does the same hold true for simply replacing the tapered bearing?


I have attached some pictures which, frankly, show some parts in damn good shape! But I attached them anyway. Some newer members might learn something. The bevel gear looked good. The crown gear looked good. No discernible signs of wear on either.  I was a little surprised that I even had to go down this road with only 68,XXX miles on the clock. Some are luckier than others! I will count myself very lucky if the tapered bearing replacement does the trick!


Any input is gratefully appreciated! Thanks.

[The Dude]

Brave move,kris.
The taper roller needs both parts matched as a pair.
Seems to me this FD was not shimmed properly in the first place.
It is crucial to set the position of the two gears up accurately on rebuilding.You may need a selection of shims to do this.All the best.

[kris]

Hey Dude,
I just watched a James Wright-Roberts youtube video of an 1150 GS FD rebuild. His contention, after having rebuilt numerous final drives, is that the shims used at the factory should be re-installed. The new bearing tolerances (sameness) are fine enough that re-specifying the shims is not necessary. After some research, it would appear that the shims take into account the differences in each housing as it is machined. I have yet to find info on how to re-shim the tapered roller bearing. There are 18 different shim thicknesses listed on "Bob's BMW part fiche" for the roller bearing.  I am not a machinist nor a mechanic. I want to do a proper job but I don't want to overly-sweat the fine details. My Beemer is one of three machines I ride. If I can pull 40,000 to 80,000 relatively trouble free kilometers out of this machine going forward I'll be happy. She is at 110,000 now and the existing situation in the FD unit shows no signs of damage, only a wee wiggle in terms of free play when tested. I will pull the outer race for the roller bearing and will replace the ball bearing. I'm in knee-deep.


Thanks for your reply.


PS - brave or stupid! I'll let you know.

[kris]

Does anyone know the brand and brand ID of their tapered roller bearing in the FD? My appears to be SKF 30305 J2. The numbers are half cut off through some kind of rotational or static wear/ chafing. Not good! The measurements on this bearing are 25 x 62 x 18.25. When I checked the part on Bob's BMW parts fiche the measurements came up as 25 x 52 x 16,25. So, now I am confused.


Can anyone shed light on this?


Thanks!

[kris]

Some further info on this project....my tapered bearing inner race did spin on its spindle. If you view the photo of the crown gear you will see the band of wear. I'm guessing that both the inner race and the spindle took a little wear. If I invert the bearing it is a little tougher to seat on the spindle (the bearing, in its correct position doesn't go all the way down the spindle due to the shim installed). So that get's the heart racing a little. Enter "bearing retaining adhesives". Thank God. The good news? People make this stuff. The bad news? It's not cheap or readily available at your auto parts store. You have to hunt it down a bit. This IS NOT thread locker. But Loctite (Henkel) does make it...#638, #648 and #680. There is also something called QuickMetal by Loctite. My mechanical friend calls it "machinist in a can". They use it all the time and swear by it.  A company called WEICON also makes this type of product. Look for WEICON 306-20. I believe these products are green in colour, whereas the threadlockers are usually blue and red. Wuerth, the third German manufacturer, makes a product simply called High Strength Bearing Retainer. When researching these various products be sure to check operating environment tolerance (ie - gear oil/ engine oil/ gasoline, etc.). Some are stronger than others. Some cure to a higher strength when heat is applied (Loctite). It makes for interesting reading and can really save the day if you run into a spun bearing scenario. Also, you may need to roughen the surfaces of the elements to be bound - use good judgement with this. Don't gouge it, clearly, but the surface should not be polish-smooth for best adhesion results.


NTN, a very reputable Japanese bearing maker produces an replacement bearing for the tapered roller FAG 30305 J2, which is what was installed on my bike. Comparable quality....waaaay less money. I am buying this bearing for $31 Cdn versus whatever BMW wants for it...I'm guessing $60-$80 Cdn. The BMW price for the big ball bearing seems to be reasonable enough. The alternate market couldn't get me one for any price nearly as low as BMW's price. Maybe they get bulk discounts!


I hope this info helps someone out there looking into their final drive or other issues where bearings are involved.

[The Dude]

I have successfully used an epoxy metal filler with high specs for stress on taper roller cups on steering head bearings.I had to hammer the steering housing back into shape using a machined up split dolly mimicking the two bearing cups all concentric.'worked well.(was crashed and ovalised).The paste took up any clearence.
I think your case was a poor fit to start with.I would expect to have to use heat to mount the bearing inner at the factory to shrink fit it onto the shaft.

[kris]

Dude, I appreciate the comments. The roller bearing is the correct size for the application. I'm not sure what would have caused the inner race to spin on the shaft. The bike did sit for 9 years, apparently. But I've put over 8,000 miles on it since purchase. Who knows...maybe we should consider putting Final Drive disassembly and inspection on the "to do" list when someone buys an old K. It's not really a big deal and could save major issues later on.

[Laitch]

The measurements on this bearing are 25 x 62 x 18.25. When I checked the part on Bob's BMW parts fiche the measurements came up as 25 x 52 x 16,25.

If it were my bike, I'd need this discrepancy settled. Of course, I probably would have just ridden it as was until it begged for my attention. :giggles Try contacting Jeremy or Drew in Parts at MAX BMW in Hampton, New Hampshire USA. Maybe they can explain it.

[kris]

Laitch, when I spoke with the rep at the local bearing shop he figured the discrepancy is due to BMW simply giving the actual bearing measurements, whereas the manufacturer gives you the dimensions of the bearing in the race. The rep said the difference in measurements made sense on that basis. The bearing is due in at the supplier tomorrow. As I complete this job I will post my findings. We all try to help each other here so why not share the knowledge gained in this instance. I can also post the NTN bearing number here and in the alternate parts list. This will save future buyers some dough over Beemer's prices. The front wheel bearings are next. I'll shop those with NTN, or other reputable manufacturers, to see what they offer. It really does pay to shop around on this stuff. Some of the price differences are wild!


I appreciate the referral to Max's.

[Martin]

Kris  see here http://www.motobrick.com/index.php?action=dlattach;topic=2252.0;attach=1883  The pinion shims are determined by the pattern on the crown wheel found by using a product called bearing blue. By coating the crown wheel with this and rotating a full turn while applying load a pattern appears on the crown wheel showing whether the pinion needs to move in or out. You then shim accordingly. See the manual attached and read the whole section on final drives. This information is only available in OEM manuals. you can download this and print the sections you require.
Regards Martin.

[kris]

Thank you, Martin. The bevel gear seems to be tight. The wear pattern on both the crown gear and the bevel gear looks, in my limited knowledge, normal/ fine. You have directly answered my earliest question regarding preload, I think. Is that what you are referring to? Or are you thinking that there is an issue with the bevel gear? (is this what you are calling the pinion?) It would help for me to know that we mean the same thing by using different terminology.


I will ask the bearing supplier for some bearing blue and do the test before a full and final install on the bike.

[The Dude]

There is a couple of things going on here.The pinion(the driver) and the crown wheel (the driven) need to mesh as designed with a rolling action metal to metal.The Engineer's blue will help visualise this and allow you to consider more or less tooth engagement.Some "backlash"is needed ie a little gap between the two meshing teeth to provide for lubrication.If this is wrong you will be able to tell by your FD being hotter than your mates'one whilst riding the same mad road.The pinion position will have some shim type adjustment with some preload to keep it in position.
  Then there's the crownwheel's end float or its negative cousin,preload,mounting between the two bearings.I expect machining accuracy has allowed for a simple assembly with only occasionally needing to add more "packing"(shim thickness)to control this,or more likely a production machine reset and scrapping the offending parts.There is also a need to consider if the two casing halves need to be adjusted in or out.My experience with this sort of engineering is the use of Gasket shims to do this,but my products' variability in manufacturing needed this to get both prelaod and gear mesh as per the design spec of the gears and the taper roller (thrust) bearings.Things to be aware of but not to be put off by.
I would hope the new parts are dimensionally the same as the old parts and the epoxy Loctite fix solves your wheel flogging about too much. :riding:

[Martin]

Read the OEM manual, might be better to print out the relevant section. If anything is not clear post your queries.
Regards Martin.

[kris]

Thank you, gentlemen.

[johnny]

greetings...

i have a spare final drive unit...

when the final drive unit on the moto pukes out gear oil... i install the spare unit and send the spent unit for rebuild...

lior the tior man rebuilds them with oe parts for 3 hundert...

why f with the booshee...

ride dangerously...

j o

[kris]

Gots no Lior the Tior man north of the 49th....gotta do it the anal way!


Update: the tapered bearing number is 30205 J2 AND NOT 30305 J2 as previously mentioned (numbers were hard to read due to bearing spin)


- bought a NTN bearing (quality Japanese brand) for $27 plus tax


- two different bearing sales reps said that the tapered bearing takes all the thrust load - the big ball bearing takes only a radial load which, by comparison I guess, is way less. That and the size difference in the two bearings - this goes against the youtube guy who says it's almost always the ball bearing. Both reps felt the ball bearing was in great shape. I'm going to stick with it.

[kris]

To finish off....the tapered roller bearing shim had worn from 2.4mm to 2.3mm (met with BMW mechanic when buying new shim and he concurred). Installed new NTN bearing (30205 or 4T-30205) with Loctite quick metal on the crown gear spindle. Checked the assembly with Permatex Prussian Blue (machinist's/ engineer's blue) and the engagement pattern looked consistent with BMW repair manual photos (thanks Martin). Upon re-assembly there is no rear wheel play (as was before). I did not disturb the bevel/pinion gear assembly (is tight), did not replace the ball bearing and, therefore, feel confident that the shim/ pre-load tolerances should stand. Time will tell. Refilled with organic 80W90 gear oil and will likely go with annual replacement thereof (it's cheap). Will likely not use moly additives (had used Guard Dog Moly additive 2 years ago - Moto Guzzi, for example, advises AGAINST using additives in their final drives).  The disassembly/ re-assembly of this unit is pretty easy and straightforward for anyone looking to investigate the FD innards. Don't be afraid. Remember to heat the tapered screws which retain the rotor before attempting removal (230F +/-, then impact drive, then continue removal while they're hot. No need for thread locker on these when re-installing. The 4 large wheel bolts retain all.
If you do a full re-build then good luck figuring out shims, etc.. Even Chris Harris at Affordable Beemer Services said he doesn't delve into this black art and Bruno is out of commission due to health reasons.

[The Dude]

Good to know you got it sorted,thanks.

[beemrdon]

Awesome post. Thanks.

My rear drive is a little loose at 3-9 (@100,000 miles). I stopped by my local BMW dealer today to pick up some parts and their "master" mechanic said that it wasn;t too bad and told me that it just needed a new bearing...he didn't mention that their was more than one.

Johnny,
do you have contact info for the Lior the Tior man? I might just buy another from ebay and get this one overhauled....I'm weighing my options.

BTW, I got a quote from my local dealer, BMW of Las Vegas today

Parts:
33111241257 O ring $9.65
07119963200  seal ring $0.50
33121242211...33121242210 grooved ball bearing $154.77
33121241938 shaft seal
33117701691 compression ring $17.83
3311766538 shaft seal $16.62

Parts Total $242.24 (plus tax)
Labor Total $470.52 @ $100+ per hour
Grand Total $732.75