BMW R1150RT tranny question. . .

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A couple months ago I dumped the factory tranny fill on the RT and put in Mobil 1 75/90 GL-5 rated gear oil. The manual recommends straight 90 weight or 80/90. A lot of other RT drivers are using the 75/90 or the 75/140 and reporting smoother shifting. My shifting was OK at first (I didn't really notice a drastic improvement), but has gotten progressively harder to downshift when cold over the last few weeks.

The first 20 minutes of riding is very difficult because of the awkward downshifting--it feels almost like the tranny is DRY. As soon as it warms up, the shifting is normal and very smoothe. And before you ask, I've double-checked the fluid level in the tranny--it's right at spec.

Is the problem aggravated because of the colder ambient temps (45-50 F) we've had, or is there something else going on that isn't related to the Mobil 1 gear oil? Would the Mobil 1 75/140 likely cure this problem? I'm leery about using the 75/140 because the manual doesn't spec that weight and the bike is still under warranty.

Thanks in advance for your opinions!

Rob
 
quote:

Originally posted by Robster:
A couple months ago I dumped the factory tranny fill on the RT and put in Mobil 1 75/90 GL-5 rated gear oil. The manual recommends straight 90 weight or 80/90. A lot of other RT drivers are using the 75/90 or the 75/140 and reporting smoother shifting. My shifting was OK at first (I didn't really notice a drastic improvement), but has gotten progressively harder to downshift when cold over the last few weeks.

The first 20 minutes of riding is very difficult because of the awkward downshifting--it feels almost like the tranny is DRY. As soon as it warms up, the shifting is normal and very smoothe. And before you ask, I've double-checked the fluid level in the tranny--it's right at spec.

Is the problem aggravated because of the colder ambient temps (45-50 F) we've had, or is there something else going on that isn't related to the Mobil 1 gear oil? Would the Mobil 1 75/140 likely cure this problem? I'm leery about using the 75/140 because the manual doesn't spec that weight and the bike is still under warranty.

Thanks in advance for your opinions!

Rob


Rob, I owned a '95 RS oilhead and my experience with a cold transmission was identical to yours- until warmed up it really didn't want to shift and this was with BMW's recommended synthetic gear oil. This is common to BMW transmissions, at least the oilhead types.
What I did was modify my warmup procedure by cranking the engine, letting it idle briefly like for 20-30 seonds then using first gear only and 2500 rpm, warming up the engine/transmission on the move for a couple of blocks (no traffic of course)in my neighborhood before pulling out into main traffic. This worked to allow the trans to shift into second once out in traffic.
Nothing wrong with the trans, just another quirk of the BMW oilhead bike. I'd stick to BMW's recommended viscosity gear oil but for sure stay with the synthetic grade.
 
BMW also makes a 75w150 gear oil. It retails for about $15 a qt. It's recommended for all BMW's made after 1970 for transmissions and differentials. I use Redline 75w140 not because it's cheaper, but because it's easier to get and probably just as good or better than the factory stuff.
 
My 96rs is sensitive to what gear-oil I put in it. Same as you, for my first gear oil change,I put in Mobil-1 75-90 and imeditly noticed it was'nt shifting right. I probably tried 4-5 different oils until the mixture thats in it now. 70% wal-mart 85-140 gl-5, 15% Castrol type F and 15% Lucas Trans-Slip. I'm not recomending other R1100-1150 owners do this, but it works in my bike. I never missed a shift untill I drained the oil that came in my bike. I drained this oil after one season and the oil looked as new as I put it in, and the magnet was spotless. So I'm not afraid of this concoction ruining the trans. I wish the magnet on my rear drive was as clean as my tranny!....black fuzz


m
 
I have hated every oil I've tried in my old school R100 since I changed it. Whatever was in it when I bought worked fine. Since I changed it I have been trying to find something better since. I tried 3 oils since buying the bike in February (14k miles ago). Next I'm going to try some cheapo Castrol 80w90.

I tried Redline 80w90 GL5, Amsoil 75w140 (severe duty), Valvoline 80-90 (so far the best but far from good) Everything I have changed it to have been very notchy, clunky. What ever was in it when I bought it worked great.
 
Thanks for all the replies. . .at least I now know that there's nothing wrong with my transmission. Now I just gotta find an oil that it likes. I'm thinking about trying the heavier Mobil 1 75/140 and see how that works. Funny thing is, the manual doesn't spec a tranny oil that heavy, but everyone seems to be using it. Also, should I put that heavier oil in the final drive as well?
 
Couple bikes I've owned did not like 140 in the rearend. It would foam or expand and end up blowing some out the vent making a mess. Fine around town but good hard runs in the desert would do bring it out. 80w90 took care of it. Think the high rotation speeds in the smallish case (compared to an auto), combined with the thick fluid made the oil just sling to the out side of the case and not drain down? climbed up to the vent hole.
 
Redline Shockproof Heavy... Both the trans and rear drive. Smoo-o-o-th. I loved my R1100RT, sold it to pay tuition for the wife's masters pursuit. I bought the first one delivered to Saint Louis when the dealership was close to downtown. It was the early build, and was shipped without a radio. That didn't come until a couple months later, and owners got their choice of a BMW branded item of clothing for their trouble. I got to watch them uncrate and assemble it. The Blue Ridge parkway, and Deals Gap were absolutely the best rides on that bike...
 
I used the Amsoil 75w140 in my 99 R1100 transmission. I never notice any trouble shifting in the cold. It did improve the clunk during high temperatures though.

Have you check the level of the fluid?
 
Yeah. . checked the level after I noticed the shifting issue. . .right at spec (bottom of filler hole). If 75/140 is so much better, why don't the engineers at BMW recommend it in the owner's manual? They recommend a 90 or 80/90. I'd think that the 75/140 would be too thick for cooler weather.
 
quote:

I'd think that the 75/140 would be too thick for cooler weather.

75w140 should have the same pour point as a 75w90. It just won't get as "thin" during high temps.

I never had a problem with the bike in the cold weather. There are many a morning that we rode of at 22-25 degrees. (electrics of coarse)

Anyhow, I would guess that 80w90 is minimum spec and they don't wont to upgrade the spec to something that is sometimes hard to find. (though that's just a WAG)
 
Well. . .this afternoon I took my wife for a ride--it was in the low to mid 70s in Central PA. The tranny shifted like crap for about the first 20 minutes of the ride. That was the last straw for me. On the way home I detoured to PepBoys and bought some Valvoline Durablend (Synthetic blend) 85/140.

I dropped the Mobil 1 75/90 and put in the 85/140 and went for a ride. My initial impression is good. I didn't have ANY shifting problems at all. I put about 10 miles on the bike in varying gears and speeds (up to about 80 MPH)--shifting was smooth and precise. I might add that I thought the 75/90 was good at first too. . .I'll keep you all posted as I get some miles on this new oil.
 
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