Transmission and Final Drive Oil Change

[pjbmw]

I am going to change the oil in the transmission and the final drive. I was going to do the final drive last winter but put it off till spring. I had bought BMW 80-90 gear oil back then. Went to the dealer to get oil for the transmission this week, and he suggested BMW 75-145. Manual says 75-145 for both. Should I get another quart of 75-145 or can I put 80-90 in the final drive and 75-145 in the transmission?

[MikeCam]

80-90 in the FD is fine. No stresses there, just work.

[johno]

I use 80-90 in both. Always have, and no problems.
Maybe if colder weather, you might have to use something thinner.

[beemerphile]

I use 80w90 in both (to which I add 5% Dow GearGard M moly additive). The 80w90 is fine in colder weather. Straight 90 wt would need to be changed out in cold weather. I forgot to do that one year on my 1977 R100RS and it puked gear oil out the vent all over the rear tire. A thrilling ride that was. - Lee

[KHaynes]

I can't see a problem with using the 80W-90. I don;t think you'll ever get the oil out of its operating temperature range.
In extremely hot or cold conditions, you'll fail before the oil does.

[iowabeakster]

i think the viscosity of the oil will be fine, more important is price.

[challey]

I changed over to synthetic for both the trans (75W-140) and FD (80W-90)at 12k miles.

At a tech seminar at last month's VT rally, John Glaves started off talking about what he's seeing as an increasingly common occurence - the failure of the FD support bearing. He stated that BMW recognized the problem and re-designed the bearing from 19 to 17 balls but that the failures are still occurring with the new bearing. He recommends 2 things. The first is to change the FD gear lube at the same time you do an oil change. The reason is not to get new fluid in the drive but to be able to check the magnet on the drain plug. Dark slushy deposit good, bits of silver bad. If there are metal chips on the magnet, there is nothing you can do except replace the bearing but a least you know in advance, before it fails on the road.

The other recommendation was to use straight 90W dino gear lube, not synthetic. He is convinced that most of the bearing wear takes place from metal to metal contact when the bike is moved from cold and believes that conventional gear lube stays put longer on the top of bearing race (and that synthetics are too thin). He acknowledged that this is not what he's recommended in the past but says he is convinced that conventional provides more consistent (i. e., cold) protection than synthetic. He also took pains to point that he still recommends synth for the transmission (75W-140) and crankcase where the operating temps and friction loads are higher.

I'll be doing an oil change in a month or so and will take the opportunity then to drain the FD and check the magnet (there were no chips in the old fluid or on the magnet when I changed the FD lube at 12k). Don't know at this stage whether I'll use dino or finish up the Red Line leftover from the earlier change.

[beemerphile]

There is another school of thought that suggests that improper preload shimming is the cause of the failures rather than inadequate lubrication. There was a good article on this in a recent RA-OTL or MOA-ON - can't remember which.

[bcbit01]

Yeah but good luck getting BMW to admit THAT one.

[bmwdave52]

Amsoil (75W-140) in the tranny and (80W-90) in the final. No problems for over four years now.