Vintage BMW Motorcycle Owners

Welcome back! I would have thought that using a GL-4 SAE 80w90 would have been the way to go. But given the age of the bike, engine oil might be the better choice.

Here's a page from an owner's manual that was printed in May 1964.

http://w6rec.com/duane/bmw/2man/page35.jpg

It suggests various grades of engine oil for the tranny, drive shaft and rear drive.

I'm kind of in the same dilemma for a newly acquired '52 R25/2. I thought that it would need engine oil for lubrication in the drive train, but when I called Vech and ordered the fluids, they sent me GL-4 SAE 80w90. I'm still not sure what I'm going to us. The user's manual I got for the R25/2 suggests engine oil.

Kurt in S.A.

Thanks Krurt I ran into same recomendation also stressing synthetic oil to prolong bearing life. (google "BMW R50/2 gearbox" to find extensive discription by duane ausherman) Still not sure what to do either. I always used engine oil in gearbox as per book but thought modern tech. might have come up with something knew. Even more interesting in owners manual is 1/2 to 1 qt./per1000 miles oil use. I know aircooled aircraft engnes are designed to burn some oil for cooling but my R50 used no noticable amount. BTW my old MG uses sae 30wt. in gearox. let me know what you decide. ....cheers frank

Welcome back to the club!

I'm not an expert, but I use modern fluids in ALL of my older bikes. My understanding is that specialty gear lubes just didn't exist for the general public until the 60s sometime, and BMW eventually issued service bulletins advising the use of gear lube, with only a change in the seals to go along with it.

You should keep in mind that gear lube "weight" numbers are measured at room temp and not engine operating temp, so 30 weight engine oil has a similar weight to 80 weight gear lube, at the temperatures your transmission and final drive are going to see.

However, this is a topic that always engenders multiple answers and no seeming definitive one. Duane's web site is a great resource, and he has a tremendous amount of knowledge about these bikes "from back in the day". But even he will tell you that he got out of it in the early 70s.

Thanks Darryl, box was rebuit in early eighties is smooth quite and oil drains clean no metal on drainplug. Since nature of seals is unknown to me plus bike will see limited use from now on I should probably stick to factory recomendations. It has worked all these years...thanks everyone for input..cheers frank

Frank -

If the tranny was rebuilt in the 80s, it's likely that newer seals would have been used. This would certainly allow for using the gear oil instead of reverting to engine oil.

Kurt in S.A.

Just for info - - I use GL-4 80W-90 gear oil in my R27 which has all original seals. No leaks.

Firt, It has been a real pleasure the last few snowy days to discover the vast pool of knowledge and good advice within this group. A few weeks ago I got the urge to dust of my 59 R50 (stored for 5 years because of ignition issue) and try to get her running. Lack of spark was traced to key switch/board and condenser. Now of coarse I have recaptured the "bug" and the old girl is getting a lot of attention. All this was promted by my renewal of my membership recently which I had neglected along with my bike. My research is pointing to areas I have neglected in the past one being oil for gearbox shaft anf final drive. Please advice on current types used both weight and brand ...cheers frank

I have also been a little unsure what oils to in Transmission, Bevel & driveshaft (R69S)........ factory manuals say engine oil but the Clymer manual states to use the 80/90 gear oil for all. I was thinking of running the gearbox oil as per Clymer as temeratures in this part of Australia are not that cold. But still not sure...

Dominic -

You have the '69 R69US, right? If so, you're good to use the gear oil and not the engine oil. By that time, BMW had changed the seals to allow use of the hypoid oil. You're only issue is going to be whether it should be GL4 or GL5. The controversy is that the GL5 could potentially have higher sulphur contents which hurts the yellow metals in the tranny. Vech is adamant about using GL4. But I've not heard of the sides of the road being littered with damaged transmissions so far...I don't think there's much to be worried about.

Yes its a 1969 R69US, thats good I'll go with the gear oil. Thanks again for your responses Kurt.
It is a great forum within this club, with some very helpful links also.