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Pinion seal woes: How I Learned to Stop Worryin' & Luv the flawed FD of my '04 K12GT

corey61

New member
Pinion seal woes: How I Learned to Stop Worryin' & Luv the flawed FD of my '04 K12GT

So, about 2½ weeks ago, before Northern California burst into flames, I set out on a solo 10-day motorcycle tour of points north of the Bay Area. Ranging as far north as Medford, OR and east as far as Yerington, NV, it was a great clockwise loop through counties with names like Humboldt, Trinity, Siskiyou, Shasta, Modoc, Lassen, and more. My intention being to make my nightly accommodations a mix of camping and hotel stays, my beloved ’04 K1200GT was burdened with more gear than I’d previously carried on such adventures. Wedged between a too-tall tank bag and a large duffel lashed across the rear seat and hard cases, I had a wonderful time on some of the less-beaten twisty byways up that way. (Pix in future posts, if anyone’s interested.)

Anyway, by the morning of Day 4, I realized two things: (1) undeniably, my front tire was much balder, after 3 days of fun in the mountains, than I’d anticipated when, two nights before departure, I paid it my first glance and, stoking my chin, sunnily opined that it would be… enough rubber to make it through the trip. Clearly, I had miscalculated. And (2), the messy streaks on my swingarm might not be just the residue of the misty rain I’d encountered the evening of Day 2, up in the redwoods along the 101 corridor and on Hwy 36 headed inland. It was looking, well… like something that had wafted up from the wet road surface and mixed with the dirt I’d acquired thus far. Again, I was wrong as to the source of the mess.

Fortunately, the plan for Night 4 was a hotel stay in Medford, and the town is big enough to host a BMW dealership – Hansen’s – which I have to plug here as a little family-operated gem. I pulled in to confirm my suspicions about the state of my tires and to throw myself upon their service department’s mercy as to the shoehorning of a tire change-out into their schedule. Happily, they worked me in. And, as all good techs do, they did a high-level inspection, informing me that (a) I had about 20% left in my rear brake pads, and (b) that mess on the swingarm? A leaky pinion seal. I vaguely recalled hearing, years before, that this is a known thing with these bikes. If I haven’t lost your interest at this point in the tale, hopefully some of you are grinning and chuckling and nodding since you know this all too well.

For the trip’s remaining six days, I monitored the state of things back there, periodically snapping pix, then cleaning it off to see how long it would take for the oily film to reappear. I was actually encouraged by the fact that hardly any more film appeared during the remainder of the trip, despite days of 90+ degree temperatures and sustained backroads cruising well into triple-digit speeds.

Upon returning home, I perused the K-bike forums for info and anecdotes about leaky final-drive seals and came up with a mixed bag: opinions and stories ranging from Oh-is-this-gonna-cost you! to Mehh… it’s not so bad: clean it up and monitor it, but keep riding; you’ll be fine for many more thousands of miles. Given my tendency to hope for the best even as I fret and stew about such things, I had intended to follow more of the latter course.

Meanwhile, reading up on FD maintenance and repair in the Clymer, I was daunted by the need for a number of special tools and a heat gun to break free Loctited fasteners, some means of fixturing heavy parts, and so on. Which probably had something to do with my decision to see no evil and hope for the best. Oh, and this was bolstered when I snipped the zip ties and rolled back the rubber boot, expecting to find teaspoons of gear oil sloshing around in there and, worst case, telltale signs of fouling farther up the swingarm, suggesting it might be worse than a pinion seal that was going. The area under the boot had but a very fine film of oil and looked surprisingly clean.

Anyway, the see-no-evil plan changed today when I dropped by San Jose BMW, where I hadn’t set foot in over a decade (long story), to be greeted by their cheery and helpful staff. A cursory glance at the swingarm-mess photo that I’d snapped on Evening 4 was all the manager needed to confirm that no, this was indeed a leaky pinion seal and it’d be best not to ignore the issue.

Bummer.

On the bright side, after I gave him a sketchy idea of my rudimentary level of competence turning wrenches, performing routine maintenance on the K12, he waxed encouraging and supportive of me having a go at disassembly, at least, and talked me through a few of the preliminary steps.

…Which brought me back to the Clymer for a second read-through of FD work, and brought me here to ask the first of what promises to be numerous questions. And, also, to write the first of a series of posts reporting progress and pitfalls as I delve, heart in throat, into final drive repair (clearly, for the first time in 14 years of owning two of these bikes) and plead for sound advice and wise council when I inevitably get stuck in the days ahead.

Ok, Sooo

With all that as preamble, I’ll confine the remainder of this long-winded post to one question for the Collective. For those of you who own a hard copy of the Clymer manual, I’ll reference page, Step, and Figure numbers, as appropriate.

Q1: Obviously, the first challenge is to remove the FD from the bike. In the end, I may not be able (or willing) to carry out all the complex surgery required to actually disassemble the pinion gear assembly and replace the seal. But if I get the FD free as a unit and take it to the dealership, that alone should save me some labor costs. It’s also an option at that point to have the shop break down the entire FD unit and service/replace all three seals. Or simply to swap in a previously-refurbished unit. More discussion to come on that, I’m sure!

Meanwhile, my first question is about the tooling required to separate the swingarm from the FD, i.e., to remove the fixed and free bearing journals (Clymer, p. 417, Steps 11-12, Figs. 11 and 13). For this, special tooling is required. My question is, Why? Referring to the Clymer text, this tooling is either BMW P/N 33 6 641 (see p. 415b) or a DIY fabrication involving welding two sockets and a connecting plate together (p. 416, Fig. 7). This tool is to be used in the disassembly as shown in Fig. 14, p. 417, to perform Step 11, p. 417. Having seen BMW P/N 33 6 641 on eBay, I think I understand that the idea is that at some point the 12mm Allen bit has to be positioned inside the 30mm socket, to avoid loosening (or tightening) both the locknut and the free bearing journal simultaneously. So the bore of the socket must be unobstructed, to pass the hex bit through it, and that’s the reason that the torque-application device (ratchet drive, breaker bar, etc.) can’t snap directly into the socket. In the DYI tool, the torque is applied to the 2nd smaller socket welded to the 30mm socket, leaving the latter’s bore clear. In the BMW tool, the 30mm socket’s wall is cut away, permitting access to its bore (for the 12mm Allen) from the side.

Can anyone please confirm or correct that understanding?

Further, consulting Fig. 14 (p. 417), I don’t see that simultaneous access to the locknut and bolt is actually needed for disassembly. And, though I haven’t studied it in detail, it seems that the need for this action occurs only on reassembly of the swingarm/FD linkage, on p. 420, Steps 18-20 and Fig 25.

Can anyone please tell me if I have this right, or I’m missing anything?

Also, if anyone has experience using the BMW tool for this, can you please comment on your experience with it? I’m not a welder and can’t fabricate the DIY tool myself (though I may be able to cajole a friend to make it for me). I might be willing to buy the BMW tool on eBay, but I vaguely recall, in my perusal of the forum threads, some discussion of the drawbacks or difficulties associated with using the BMW tool.

Finally, if any of you who have read this far have actually performed the pinion seal replacement yourself, can you offer me any general, high-level guidance at this point? Something along the lines of either:

(a) If you don’t have auto-mechanic experience and a well-equipped shop and comfortable workspace, you may be getting in over your head. Seriously consider opening your wallet and extracting a sizable wad of cash to let the dealer do it.

(b) You can do this! Take it slow, be systematic, study and follow the Clymer procedure rigorously, document your steps with photos and video notes, work carefully, and you’ll be fine. And you’ll be filled with the satisfaction that you tackled and mastered this elaborate but far-too-necessary process for dealing with this particular design weakness of these bikes.

Please, save any detailed comments or instructions, notes, or diagrams for a bit later in this journey, if they aren’t germane to the 50,000-ft perspective I need at this point, when deciding whether (a) or (b) is the narrative closest to my reality.

And, as always, many thanks in advance!

Best regards,
Corey
 
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I have rebuilt over 130 of this style final drive. I would not worry about a leaking pinion seal. It also could be a leaking transmission output seal. Neither seal leaks enough to cause any damage if you keep the final drive or transmission gear lube level close to the full fill level. If you use the zip ties with the stainless steel tab and pull them tight with pliers on the rubber boot it can stop the leak onto the swing arm. The easy way to find out which seal is leaking is to change the gear lube in both final drive & transmission using two different brands of gear oil with different colors. After a 1000 miles or so pull the boot back & see what color lube drains out.
 
I have rebuilt over 130 of this style final drive. I would not worry about a leaking pinion seal. It also could be a leaking transmission output seal. Neither seal leaks enough to cause any damage if you keep the final drive or transmission gear lube level close to the full fill level. If you use the zip ties with the stainless steel tab and pull them tight with pliers on the rubber boot it can stop the leak onto the swing arm. The easy way to find out which seal is leaking is to change the gear lube in both final drive & transmission using two different brands of gear oil with different colors. After a 1000 miles or so pull the boot back & see what color lube drains out.

Dave,

Wow! That's a whole lotta FD rebuilds! Your response was on the side of the spectrum Mehh… it’s not so bad: clean it up and monitor it, but keep riding...; I'd seen that expressed on another forum. That's encouraging and it makes it very tempting to go down the "see no evil" path!

Today, I cracked open the FD oil fill port to see what I could see about how much oil I'd lost. The level was just shy of the bottom of the fill port, i.e., virtually full. I'd also been considering draining the FD so I could inspect the magnetic drain plug and document the amount of metal filings stuck to it. Perhaps I'll do that and refill with red gear oil, so I'll then have amber-colored oil in the transmission and red in the FD. I'm aware of what you say, that it could also be a transmission output seal - which if I understand correctly, would be a more serious problem.

Given your response, I'm hoping to hear from some more wise men of this forum for a chorus of opinions. In any event, your 130-FD-rebuilds experience would be invaluable if I do decide to proceed with fixing the pinion seal. Thank you for weighing in!

BTW, where can I source the zip ties with the stainless steel tabs? After trying to find correctly sized zip ties elsewhere, I finally gave up and ordered some OEM parts from the BMW dealer. They were the nylon version, though.

Best regards,
Corey
 
A very small amount of gear oil can make a huge mess when spread around a little bit. And many/most/all pinion seals on BMWs seep a little bit. Clean it up inside the boot and out and repeat after 12 or 20 thousand miles has been my experience.
 
A very small amount of gear oil can make a huge mess when spread around a little bit. And many/most/all pinion seals on BMWs seep a little bit. Clean it up inside the boot and out and repeat after 12 or 20 thousand miles has been my experience.

Ok, so you're the 2nd person to weigh in with the opinion that this is not something requiring immediate attention. So I think I have it on good authority...

Here's the mess I mentioned in my long narrative, the evening of Day 4 of my trip:
 

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I have rebuilt over 130 of this style final drive...

Dave, just as background info, can you say roughly what a rebuilt final drive costs, if someone wants to take that route? I'm not going to do that any time soon, just want to file away the info. Thanks.
 
Ok, so you're the 2nd person to weigh in with the opinion that this is not something requiring immediate attention. So I think I have it on good authority...

Here's the mess I mentioned in my long narrative, the evening of Day 4 of my trip:

That is messier than many I have seen but it is still worth the effort to clean up the exterior and peel the front edge of the boot back and thoroughly clean inside the boot and the interior of the swingarm. Put it back together and then peel the boot back after 1,000 miles or so to see what you've got.
 
That is messier than many I have seen but it is still worth the effort to clean up the exterior and peel the front edge of the boot back and thoroughly clean inside the boot and the interior of the swingarm. Put it back together and then peel the boot back after 1,000 miles or so to see what you've got.

Paul,

Right - I think that's why the dealership guy just took a glance at it and declared that I have a pinion leak that needs attention. The mess first appeared the evening of Day 2 of my trip, after I'd ridden through a light rain - heavy enough to lightly wet the road and my helmet visor, but not enough to get me wet inside my riding jacket. At first, I thought it was just normal schmutz (technical term!;)) from riding in the rain. But clearly some oil had leaked out, at that point. I cleaned it up periodically for the remaining 7 days of the trip and took pix before each wipe-down. Was happy to see that little to no additional leaking occurred. :clap

Over the past week, I've cleaned it thoroughly, both outside and under the boot. That's been relatively easy (to do it thoroughly) since I've had the rear wheel off the bike to change rear brake pads, allowing me access to the inboard-facing nooks and crannies on the exterior of the swingarm.

I will follow your guidance, with some relief; I wasn't looking forward to a replacement of the pinion seal, whether by me or a qualified shop.

Thanks again for your advice!

Best regards,
Corey
 
I tell my customers to let pinion seal leaks slide until they get tired of wiping the oily residue off. It doesn’t hurt anything and the amount lost is negligible.

If you don’t have the right tools, it’s definitely not worth getting into. Here, it would be a two-hour ride in, ride out job when all is said and done.
 
Colored Gear oil..??

Hello All,

So, I've taken the advice that a number of you gave and, after cleaning up the area under and around the final drive boot thoroughly, zip-tied it back in place and will monitor the situation.

One thing that remains unconfirmed is that the leak is indeed from the pinion seal rather than the transmission output seal (I'd give it an 85% chance). It was suggested that I change the gear oil in either the FD or the transmission to one that's a different color. That way, when it leaks again I'll be able to positively identify which seal is the leaker.

Seems like a good idea to me. Question is,

Can anyone tell me of a colored hypoid gear oil that I can use? I vaguely recall that there is a red-colored product out there, and I thought it might be by Red Line. But when I asked that question on Amazon, the response was that Red Line's hypoid oils are natural amber-colored.

Thanks.
 
Hello All,

So, I've taken the advice that a number of you gave and, after cleaning up the area under and around the final drive boot thoroughly, zip-tied it back in place and will monitor the situation.

One thing that remains unconfirmed is that the leak is indeed from the pinion seal rather than the transmission output seal (I'd give it an 85% chance). It was suggested that I change the gear oil in either the FD or the transmission to one that's a different color. That way, when it leaks again I'll be able to positively identify which seal is the leaker.

Seems like a good idea to me. Question is,

Can anyone tell me of a colored hypoid gear oil that I can use? I vaguely recall that there is a red-colored product out there, and I thought it might be by Red Line. But when I asked that question on Amazon, the response was that Red Line's hypoid oils are natural amber-colored.

Thanks.


From my experience Red Line gear oil is red in color, but I had a very good riding buddy who put it into his K1200RS gearbox and it went all weird colored on him and the shifting became difficult. He drained the Red Line and flushed the transmission with conventional gear oil and then refilled and things went back to normal. I think I still have an unopened quart you can have for the shipping.
 
Ditto, and I really like the color difference between my tranny oil (their red) and my rear drive oil... just in case...
 
Some of Bel-Ray's oils are red...


Sounds good. I'm researching Bel-Ray oils...

Would you happen to know the specific Bel-Ray gear oil that's red in color? So far, I haven't found that info online, though I've posted the question several places.

Corey
 
From my experience Red Line gear oil is red in color, but I had a very good riding buddy who put it into his K1200RS gearbox and it went all weird colored on him and the shifting became difficult. He drained the Red Line and flushed the transmission with conventional gear oil and then refilled and things went back to normal. I think I still have an unopened quart you can have for the shipping.

Greg,

Thanks for the offer, but given your comments and the recommendation of Bel-Ray products, I'm looking in that direction.

BTW, seems to me that the new gear oil could go in either the tranny or the final drive, since they both take the same oil spec. Any reason why NOT to use either the Bel-Ray or the Red Line oils in the FD? To do this, I'll have to drain either the FD or the tranny and the former seems a bit easier...

Corey
 
Just looked at the Cycle Gear website (since there are two of 'em near me), and Bel-Ray has changed the packaging... When I bought it (several times) a while back, their Gear Saver 85W-140 synth GL-5 trans oil was red.
I don't know the spec for the oil you need in there, but keep in mind that nnW-140 is NOT to be used in the opposed boxers' rear drives. There is a difference; it seems that the multi-weight would get pushed ahead of the bearings instead of flowing into them.
They also have a straight 80W gear saver oil, also GL-5 rated, but I don't know its color.
 
Just looked at the Cycle Gear website (since there are two of 'em near me), and Bel-Ray has changed the packaging... When I bought it (several times) a while back, their Gear Saver 85W-140 synth GL-5 trans oil was red.
I don't know the spec for the oil you need in there, but keep in mind that nnW-140 is NOT to be used in the opposed boxers' rear drives. There is a difference; it seems that the multi-weight would get pushed ahead of the bearings instead of flowing into them.
They also have a straight 80W gear saver oil, also GL-5 rated, but I don't know its color.

Thanks for checking. I found a short video on Bel-Ray's website about their hypoid gear oils:
https://www.youtube.com/watch?v=iZq5Zq-UCeU

It's available in two weights - 80W-90 and 85W-140. And indeed, it is apparently red (according to the video).

I've ordered a liter of the 80W-90 on eBay. Should work fine in either the transmission or final drive of the K1200GT. I'll put it in the FD for two reasons: (a) it's easier to change than the tranny oil; and (b) if it's the pinion seal that's leaking - and I'm betting it is - then in 1000 miles or so when I pull back the FD boot, I should see red oil underneath.

Corey
 
Thanks for checking. I found a short video on Bel-Ray's website about their hypoid gear oils:
https://www.youtube.com/watch?v=iZq5Zq-UCeU

It's available in two weights - 80W-90 and 85W-140. And indeed, it is apparently red (according to the video).

I've ordered a liter of the 80W-90 on eBay. Should work fine in either the transmission or final drive of the K1200GT. I'll put it in the FD for two reasons: (a) it's easier to change than the tranny oil; and (b) if it's the pinion seal that's leaking - and I'm betting it is - then in 1000 miles or so when I pull back the FD boot, I should see red oil underneath.

Corey

For the last 18 years I have used the same "Bel-Ray Hypoid Gear Oil" in the 80W90 grade - both in the transmission and the rear-drive. This Bel-Ray gear oil is RED and meets the requirements /specs specified in the K1200RS BMW shop manual and owner's guide (for both transmission and rear-drive). I never had a leak so had there was no need to try different color gear oil in both zones / areas.

Bought my K1200RS new in 2002 and except for the 1st inspection at 600 miles (1000 KM) done at dealer, after this for the last 18 years I have done all the maintenance myself. Since mid 2002, my K1200RS has never seen a dealer (except bringing them the wheels to mount tires in some occasion).

Depending on mileage done during a year (varies from 4,000 to 10,000 miles), I would change transmission oil about every 2 years and rear-drive oil every year. This tigher intervall for rear-drive was mainly a visual monitoring mechanism for metallic deposits in rear-drive. My K1200RS now has 97,000 miles (157,000 KM).

Although I have seen a few problematic rear-drives on K1200RS/GT and K1200LT (friends), mine has been fine all these years. Anectodal evidences from many large BMW user groups (and meeting at rallyes), shows that having a bad one is a crap shoot - many are good some are bad... The shimming and built tolerances of all parts is critical (amost an art) and the factory has not always been on top of things for the quality control.
 
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