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Using 75W-90 or 75W-140 when changing oil in transmission/final drive

1111 Views 11 Replies 9 Participants Last post by  Fez
Did any of you see any advantages using 75W-140 over the 75W-90 the bike comes with from the factory? I heard that there are quite some dealers who move to 75W-140 during the 1000KM service, while some others stay with the same type of 75W-90.
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75W-90 is recommended by our trustful bavarian engeneers - why not just do so?
I doesn't matter, depending on your availabilty. Difference is only the price.
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For the sake of warranty and plausible deniability, stick with manual recommended type/viscosity.
I'd be interested to know where you came across this info

I havn't tried a different grade in the BMW yet but have been considering it, that's why I'm interested in any data points.

I know some Guzzi owners use a 75/140 oil in the old 5 speed boxes in preference to the recommended 80/90 recommended, stating it assisted in making gear changes less noisy and improved the gearchange.

I don't know much about gear oils though but I do know that the viscosites quoted are different from engine oils.

I've seen that a couple of folks on here run Redline Shockproof Heavy. I've used it in some Guzzis and found it was an improvement for a while but gradually degraded. I moved away from it as Redline don't produce a data sheet for it and won't give you any info, nor does it meet recognized approvals. That said there are many folks using it, Harley owners love it and many Guzzi owners use it too and I've not heard of any failures. It's incredibly sticky looking and viscous, to the point of being a PIA to drain.

I'm not recommending it, just pointing it out. Of course running a different grade to recommending could get you into trouble with any warranty defects claims as pointed out

Temperature changes in the gearbox will also be much lower than the engine, just a guess but I'd think gearbox temps would be around 60-70C where an engine would be closer to 100C.
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I move countries a lot, and thus move dealers quite often. And multiple dealers I used for service parts, said they were using 75W-140 instead of the "recommended" 75W-90. Moreover, here its not often talked about, but if you check the German NineT forum, there are quite some guys swearing using 75W-140 as their gearbox and bevel gear oil.
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I use 75W-140 in the bevel gear mainly because I keep a supply for the limited slip diff in my car. I don't plan on using it in the gearbox, but I don't see it doing any harm in the bevel drive.
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balance, your final drive and your gearbox
5
...but if you check the German NineT forum, there are quite some guys swearing using 75W-140 as their gearbox and bevel gear oil.
Do they say what the advantages have been ?
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... let's say it is still 50:50 (in many Boxer forums) - some mention a smoother shifting with 140... some not !? Could be useful at higher temps - ..or not !?

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View attachment 159877 View attachment 159878

... let's say it is still 50:50 (in many Boxer forums) - some mention a smoother shifting with 140... some not !? Could be useful at higher temps - ..or not !?

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Thats exactly why I am asking it here Tom. On the German forum people are almost fighting about what to use, and here I rarely see it mentioned, so I thought people would be a little less influenced here with their opinion on the matter haha.

Dealers seem to be rather 50/50 as well. I had some tell me they change all of them to 75W-140 at their 1000km service, while others told me to use 75W-90, keep using 75W-90, and never ever change it to anything else than 75W-90.
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Been using the 75/90 so far, however we are going into our Australian summer, I may change prematurely to the heavier stuff.
My understanding is that the word Hypoid must be in the description rest is resolute upon you climate and usage. Hypoid refers to the gears used in the final drive and using Penrite has also improved the gear shifting.
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