Tiny metal flakes on the drain plug -- should I be worried about my transmission?

Hey again, mechanical minds of the MOA. I am happy to report that my sad Oilhead (1997 R850R built in August of 1996) has been running perfectly for a couple months now and I haven't had a single issue. This is me wanting to know about possible problems in the future.

When I first got the bike, it had 34,500ish miles, and because I knew it had been sitting for years I changed all the fluids out. I looked carefully at the magnetic drain plugs for both the final drive and transmission when I did that.
The final drive plug had a decent amount of very dark sludge on it, kind of like a ferrofluid. It was more than enough to cover the magnet entirely.

The transmission drain plug had a lot of that same dark sludge, but also what looked like extremely fine metal glitter, kind of like nickel anti-seize. There were no pieces larger than...maybe the width of a human hair? Teeny flakes, but very shiny. The transmission drain plug magnet was also not visible due to the amount of magnetic material it caught. There was quite a lot.
I should also mention the transmission fluid, whatever the previous owner put in, came out dark and very opaque and smelling somewhat burnt.

At the time I put Mobil 1 synthetic 75w-90 gear oil into both the final drive and the transmission. I didn't think ahead and bought only 1 quart, so I captured maybe 300ml of the previous transmission oil and reused it mixed with the new stuff while the final drive got all new oil. I knew at the time that it would only be in there for 1500 miles so I figured it wouldn't blow up.
I was right, it didn't blow up, but for the record I'm not ever doing that again unless it's an emergency. I should've just bought two quarts of conventional gear oil. Lesson learned, etc.

Fast forward to now, at 36,080 miles, and I have changed the three main fluids again. The magnetic drain plugs for both the final drive and the transmission came out with pretty much the exact same materials on them, but probably less than half as much volume of it as before. Dark magnetic sludge on both, and very fine shiny flakes on the transmission drain. Again, the transmission fluid came out smelling burnt, but this time it was less dark and had some parts that looked much lighter, like parts of the oil were separating.

I put Red Line 80W synthetic transmission oil (with "shockproof) into the transmission this time, and put conventional Maxima 80w-90 gear oil into the final drive. I noticed an immediate difference in shifting performance. Both up and downshifts are noticeably smoother and the gearbox is quieter all the time. The shift clunks no longer sound like an angry gremlin with a hammer is trying to escape my transmission.
That Red Line stuff looks weird. I guess the additive package makes the oil look totally opaque when it comes out of the bottle, which isn't like any other gear oil I've ever seen. It looks like some kind of crimson latte.

I've perused Anton Largiader's info on M97 transmissions but can't really find anything definitive. His reference to the input shaft wear issue matches what I've seen and smelled in my oil but he doesn't mention fine metal flakes in that article.

What I want to know is: are my burnt-smelling transmission oil and fine metal flakes on the drain plug at both changes 1500 miles apart a sign of future transmission woes? Can I delay or avoid future transmission problems by continuing to use this Red Line synthetic oil?

Did the metal flakes feel gritty between your fingers?
The burned smell is not a good sign.

Unfortunately I did not touch them directly so I cannot give you a clear answer there, but they looked so small that I'm guessing I wouldn't have been able to feel them.

I have always been advised not to use synthetic in the older Transmissions and final drives. My dealer recommends to make sure to use a Non-synthetic Hypoid 90 wt. gear oil.
Could the smell be a sulfur type smell???

jrogers said:

I have always been advised not to use synthetic in the older Transmissions and final drives. My dealer recommends to make sure to use a Non-synthetic Hypoid 90 wt. gear oil.
Could the smell be a sulfur type smell???

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Good point. Tom Cutter at Rubber Chicken Racing has the same opinion - especially in the final drive.
SAE 90 Hypoid as per BMW spec.

There is a school of thought that synthetic gear oil allows the balls in the big bearing to skid instead of roll on the races.

Makes sense -- and I just double-checked the official manual myself, which repeats SAE 90 GL-5 "all year round". My Clymer manual for Oilheads differs; it says "80w in winter, 90w in summer, alternative 80w-90" GL-5. Unfortunately, straight 90 weight oils are getting harder to find in consumer sizes. I'll have a look around.

I also just noticed (which I hadn't before) a conspicuous absence of a GL-5 rating on the Red Line oil I just put in. Wuh-oh.

I'd be fine with swapping to mineral if I knew what I was getting was good stuff, but it seems like regardless of what I choose to replace it with I should change out what I just put in.

If the burnt fluid and metal flakes are a sign of trouble, I hope this transmission lasts at least another 6,000 miles.

I use 80w90 with no issues.
Stay non synthetic.

senseamidmadness said:

Makes sense -- and I just double-checked the official manual myself, which repeats SAE 90 GL-5 "all year round". My Clymer manual for Oilheads differs; it says "80w in winter, 90w in summer, alternative 80w-90" GL-5. Unfortunately, straight 90 weight oils are getting harder to find in consumer sizes. I'll have a look around.

I'd be fine with swapping to mineral if I knew what I was getting was good stuff, but it seems like regardless of what I choose to replace it with I should change out what I just put in.
.

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Tom Cutter, who rebuilds these transmissions for years, recommends strongly, Castrol 80w90 Hypoid GL-5 gear oil. They changed the name on the bottle a few years ago to Axle Limited Slip, but it is the same product. Available at most auto parts stores.

I tried the Red Line in one of my Harleys years ago and took it out within 100 miles. It made the tranny sound terrible and shifted bad too.

I'm using my 04 R1100S Boxer Cup for Track Days only and my dealer told me to use the heaviest Non-Synthetic Hypoid gear oil I could find. So I found Valvoline 85-140 at the auto-parts store and used it. It has made for smoother shifting and a much quitter tranny, probably going to use it in my other bikes when I change their fluids.
https://www.amazon.com/Valvoline-85...ocphy=9032555&hvtargid=pla-527491793230&psc=1

m_stock10506 said:

Tom Cutter, who rebuilds these transmissions for years, recommends strongly, Castrol 80w90 Hypoid GL-5 gear oil. They changed the name on the bottle a few years ago to Axle Limited Slip, but it is the same product. Available at most auto parts stores.

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How very convenient -- my local O'Reillys has that in stock right now for less than $9 a quart, and its specs look really good. Easily as good as the Lucas gear oil I was eyeing and a it's bit cheaper. I'll pick up a quart tomorrow and get it changed out before the Red Line has time to do any damage.

jrogers -- does your having a 6-speed transmission have any impact on that viscosity recommendation? I have heard that they're very different gearboxes.

senseamidmadness said:

How very convenient -- my local O'Reillys has that in stock right now for less than $9 a quart, and its specs look really good. Easily as good as the Lucas gear oil I was eyeing and a it's bit cheaper. I'll pick up a quart tomorrow and get it changed out …..

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If it gives you any further comfort, I have been using the 80w90 Castrol gear oil for about twenty years, in my two Airheads and my two 1100RTs. The current Oilhead had the gear box rebuilt almost immediately after I bought it due to a failed input shaft. I have put about 184k miles on this bike since. The gear box hasn’t been opened since.

That does, at least a bit. I'm worried mine may still have the input shaft gear wear issue and swapping fluids probably won't fix that, right?

senseamidmadness said:

That does, at least a bit. I'm worried mine may still have the input shaft gear wear issue and swapping fluids probably won't fix that, right?

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Yeah. The part of the input shaft that fails is the part that is outside of the gearbox, mating with the clutch friction disk hub. It's the splines of the shaft and the clutch that sometimes wear excessively and then fail. That surface requires a heavy grease. They say that if there's an offset between the two parts, no amount of grease will prevent the wear.

m_stock10506 said:

Yeah. The part of the input shaft that fails is the part that is outside of the gearbox, mating with the clutch friction disk hub. It's the splines of the shaft and the clutch that sometimes wear excessively and then fail. That surface requires a heavy grease. They say that if there's an offset between the two parts, no amount of grease will prevent the wear.

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True, but clutch hub and input shaft wear would not show up in drained transmission gear oil.

I have used GL5 Castrol 80W90 Hypoy C (recently renamed Castrol 80W90 Limited Slip) gear oil for several hundred thousand miles in various bikes. It is what Tom Cutter recommends and uses. I find no reason to use anything else. Among other bikes, my R1150R had 189,000 miles on the transmission, unopened and working fine when I sold the bike. Voni's R1100RS needed transmission repair at 349,000 miles.

I'm referring to this issue regarding one of the gears on the input shaft: http://largiader.com/tech/oiltrans/m97.html

I haven't done a spline lube on this transmission but it's on the list of stuff to do eventually. If I have transmission problems I might want to do a lot more than just that when I eventually remove the transmission.

It's a bit hard to say since it wasn't all clean oil when you changed, but if the oil is turning dark so quickly and you get the burnt smell, you need to deal with the input shaft. Could be that the bearing is getting pushed hard enough by the gear that it is failing.

AntonLargiader said:

It's a bit hard to say since it wasn't all clean oil when you changed, but if the oil is turning dark so quickly and you get the burnt smell, you need to deal with the input shaft. Could be that the bearing is getting pushed hard enough by the gear that it is failing.

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Do you think it would be dangerous to put off transmission removal until the next service interval at 42,000 miles? It currently has 36,140 or so. And have you ever seen any input shaft gear/bearing failures near this mileage?


Also, an update related to previous posts in the thread. I drained out the Red Line from my transmission and put in the Castrol today. I really thoroughly cleaned the drain plug again out of curiosity and it looked like it had just a bit of anti-seize compound stuck to the sides of the magnet. Sparkly, but all metal pieces so small that I couldn't feel them.
I also changed out my clutch cable (the old one had cracks in the outer sheath and visible rust inside) and set the free play and the barrel adjuster to the 7mm/12mm spec.

First ride impressions are...well, not great, comparatively. It's exactly the way it was with the Mobil mix before the Red Line. Clunky, noisy, and whiny. Significant whine on acceleration, worse on deceleration in gear. Shifts feel like they take a bit more force to achieve and I can hear and feel them a lot more. It functions fine, other than me adapting to the "correct" clutch adjustment (it feels so different now that it had to have been very wrong the way the previous owner set it) and the oddly more difficult pull with the new cable. However, the Red Line made a big difference in noise and feel and I'm surprised that it seems significantly worse with the Castrol.

I don't regret pulling out that previous gear oil because it had no testing standards anywhere on it, but it makes me wonder whether there's an additive or another oil I could use to do what it did. Or maybe my transmission is just on the way out and I have no frame of reference -- is noisy and whiny and clunky normal?

senseamidmadness said:

Do you think it would be dangerous to put off transmission removal until the next service interval at 42,000 miles?

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Well, you're describing transmission failure with practically every sentence you write. The worst one I saw had the owner (passing through) flying home to Canada while I trailered his bike from his motel to my shop. Maybe yours will go a while before you get to that point, but I sure can't predict for how long.

They are fairly noisy and clunky to begin with. Do you have another to compare with in your area?

jrogers said:

They are fairly noisy and clunky to begin with. Do you have another to compare with in your area?

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I have to add my two cents. Clunky, yes. Noisy, no.

To the OP, read the first sentence of post #18 again and then make your decision.