PDA

View Full Version : Pressure in Final Drive



jacko
05-30-2009, 09:47 PM
Greetings,

Bike is a 2006 R1200RT 23000 miles and I had a unusual experience this morning that I really don't understand.
I rode over to gas station early this morning to gas up. About a 3 mile round trip. The bike felt a little tight when rolling so when I got home I gave the wheels a spin. The housing on the final drive was quiet warm. For no reason I loosened the fill plug on the final drive and I got a phush---. It was pressurized! Wild guess is maybe 2~3 pounds. Oil level is filled to new specs(180cc's I believe without looking it up). Techs at dealer have never experienced this but was noted just in case of future problems. Anyway can someone explain this to me?

Jack

Semper_Fi
05-30-2009, 11:58 PM
How did it perform after you "depressurized"?

Was it still tight?

What was the last thing done to the bike before you went to the gas station?

jacko
05-31-2009, 01:33 AM
After depressurization normal drag feeling when rotating rear tire.
Other than a oil change/tune up a couple a weeks ago nothing done. haven't washed it for awhile so probably not steam pressure. how would water get in anyway. Any body else tried loosing the plug after a good warm up ride?

Why would there be any pressure in it anyway? Will take a long spin into the hills tomorrow an see what it's like when I get home.

henzilla
05-31-2009, 02:21 AM
What is your home elevation compared to the dealer?

We had a 05RT riding with us that weeped from the outer seal in Taos, but stopped when it got to 800' above sea level back in West Texas. I have to think, no vent on the FD like the old style did has to have some effect at higher altitudes.

jacko
05-31-2009, 12:43 PM
Elevation isn't a factor as Foothills bmw is just down the street.
Older FD's were vented, new ones are not? Why the change in engineering?
My experience with bmw only goes back four years, goldwings before that. Each bike has it's oddities and this pressure thing isn't much of a deal so far. Have never seen any bleeding on my walk arounds.
It would be of interest to me if some of the other RT/GS hexhead riders that have bikes built before BMW put the drain plug back on the FD's have a pressure build up after a warm up ride.

Jack

Polarbear
05-31-2009, 01:09 PM
I figure it to have a pinhole somewhere to releave the pressure, as I have never seen a gear box without some kind of release(vent) to the open air. It may be very hidden in the design, but most probably present somewhere. 235cc is the number for the oil in the FD, or very close. GSA1200 here. Its a pretty tough unit too, despite all the fails posted, as I ran 170cc in mine for the first 5000 miles, under dealer service, to find it had way too little in there. They(BMW) had made a mistake and I have 35000 now, without fail:). It never got hot with less oil, as I frequently checked it due to all the reading here about fails. Randy PS; it may still fail, but I'm hoping not:):thumb :usa

darrylri
05-31-2009, 01:26 PM
The final drives before 1962 had no venting. None of my bikes from before then leak, except the 1928 R52, which doesn't seal well where the shaft enters.

Actually, the R52 is lot like the R1200s in that it has no drain plug on the final drive. To empty it, you remove the rear wheel, unbolt the final drive from the frame, remove it and the attached driveshaft, open the fill bolt and hold it with the shaft up over your oil recepticle. What's old is new again!

deilenberger
06-01-2009, 03:34 AM
I'm not a BMW engineer - but the idea of a sealed unit is to prevent contamination of the oil. Contamination is probably the biggest factor in rear-drive oil breakdown. Use of the oil isn't. I could see an engineer deciding that the rear drive could be sealed, and at most it might pressurize to a few PSI - which the seals should be able to contain without a problem. Since BMW wanted this to be a sealed-for-life design, it's understandable that it has no vent.

Polarbear
06-02-2009, 02:34 AM
Good vents will not contaminate the oil. I've worked in a gear shop for years and have found trannys and gear boxes quite happy(clean oil) with vents and clean oil after a lot of miles. My experience with contamination is almost always bearing heat/failure and gear wear, bad shifting habits, etcetc in large rigs. Even with bad habits and shearing of the gears, the oil still comes out quite new looking in many cases, however with pieces in it. Randy:thumb :usa

deilenberger
06-02-2009, 03:40 AM
Randy - I'm afraid I'll have to disagree.

The gears you're looking at are probably not running in all sorts of weather, and the vents aren't exposed to rain. Think about a rear drive that is nice and warm from use, and you run into a good rainstorm. Or on a GS - you do a water crossing. The rain/water cools the drive, and if there was a vent, it would draw any moisture on the vent into the rear drive, contaminating the oil. Even a Gortex protected vent will draw water vapor through the membrane. If - as BMW was - you're seeking a no-maintenance gear environment - any contamination of the fluid isn't acceptable.

On older K bikes - it's fairly common to have the vent barfing out lube oil when the rear drive gets hot enough, the reason being the oil is contaminated with enough water that it starts steaming and pushing lube out the vent along with the steam.

A sealed system is IMHO very desireable, if the expansion of the fluid can be accomidated. A non-venting expansion diaphram would be one way to handle it.. allowing for expansion without any air being sucked into the drive when it cools.

Also note the reduced quantity of oil - as I've read it - is only the "refill" quantity, not the initial dry fill quantity. I suspect part of the problem with over pressure in the rear drives was an excess of lubricant due to inadequate draining of the old fluid when doing a change.

jacko
06-02-2009, 11:29 PM
Tuesday and I'm finally getting back with you-all.
Sunday went out for another spin and when I got back I pulled the plug again and very little to no pressure or oil blow out. I have a feeling that at least part of the problem was to much oil.
Let's go back three years. 600 miles was done by dealer had FD oil changed at that time even though It wasn't called for. 6000 mi dealer normal called for service. This was getting expensive so decided to 12000 myself except for the FD and that the dealer did as I started reading a lot about FD failures and felt that if I did end up with A FD failure at least the dealer had did that service. Last week I went through the whole bike gearbox etc. plus tune up. Didn't do the FD because I couldn't get the rear tire off ( need a bigger breaker bar!) Did read about the new level of fluid so that's why I unplugged and got the whoosh and some oil out of the plug hole.
Don, I think you are close as to the reason why. And In my number of years of playing most of the gear boxes that I have seen have been vented somehow.
BMW is different and they do have their way of doing things.
Thanks for the inputs and hope to meet up with you in Tenn.

Jack

Polarbear
06-02-2009, 11:55 PM
Thats ok too to disagree. I'm happy with it:). My K bike never slopped any oil out the FD. All my changes of FD oil, done by me have been clean, like new oil coming out. I ride dirt and rivers, rain and all the bad stuff, weather wise. Go figure. I've never had a contaminated FD oil, but have heard of them! Got me looking now, for a vent hole:). Probably not there. Randy....Tenn.,YES, R1200GSA:thumb

BrianVivian
06-03-2009, 02:58 PM
What is your home elevation compared to the dealer?

We had a 05RT riding with us that weeped from the outer seal in Taos, but stopped when it got to 800' above sea level back in West Texas. I have to think, no vent on the FD like the old style did has to have some effect at higher altitudes.

Uh oh...now you guys have me worried. I'm sitting at 1100 feet right now and will be taking the bike to Colorado this weekend where it will see 10,000+ elevations. Do I need to worry about venting pressure in the final drive?

henzilla
06-03-2009, 05:01 PM
Uh oh...now you guys have me worried. I'm sitting at 1100 feet right now and will be taking the bike to Colorado this weekend where it will see 10,000+ elevations. Do I need to worry about venting pressure in the final drive?

Wouldn't lose sleep over it, many trips from 800' to 10,000+ on hexheads without issues. We just noticed that fellows bike doing it and were head scratching.

BrianVivian
06-03-2009, 05:44 PM
Wouldn't lose sleep over it, many trips from 800' to 10,000+ on hexheads without issues. We just noticed that fellows bike doing it and were head scratching.

Good to know, thanks!

Wallowa
06-06-2009, 11:33 PM
Greetings,

Bike is a 2006 R1200RT 23000 miles and I had a unusual experience this morning that I really don't understand.
I rode over to gas station early this morning to gas up. About a 3 mile round trip. The bike felt a little tight when rolling so when I got home I gave the wheels a spin. The housing on the final drive was quiet warm. For no reason I loosened the fill plug on the final drive and I got a phush---. It was pressurized! Wild guess is maybe 2~3 pounds. Oil level is filled to new specs(180cc's I believe without looking it up). Techs at dealer have never experienced this but was noted just in case of future problems. Anyway can someone explain this to me?

Jack

Another forum had an interesting take on what could happen with excessive pressure in FD: pressure could press seals too tightly against shaft and result in excessive seal wear...

I will add that less lube = more heat and probably more pressure not less in FD..if the seal theory is valid then tighter seal = friction=drag you felt...just a WAG.

My BMW DVD states 220 ml on refill for my '07GSA...I have never received anything from BMW telling me to refill to 180 ml [bulletin only goes to dealers]...but just for me, less lube = more heat [lubricants also cool surfaces] = more heat/friction = accelerated wear.

As for sealed VS non-sealed FDs...Diffs for my '62 Corvette come in two flavors, vented and unvented...vented is only on the Positraction diff since the plates generate more heat...and the 4 speed trans is not vented...guess what, the seals do not leak on the non-vented versions...but then again BMW did not engineer it...

Just for me..;)

marchyman
06-07-2009, 04:45 AM
less lube = more heat [lubricants also cool surfaces] = more heat/friction = accelerated wear.

Uhhh, not always. Sometimes it is the opposite that occurs. The book "Systematic analysis of gear failures" (I love google!) states:


"Excess lubrication presents some unusual problems in a gear train. The churning effect resulting from excessive lubrication can raise ambient temperatures, because the energy involved in cutting the shear plane of the oil is reabsorbed as heat. A continual churning of the oil, along with increasing temperatures, will tend to solidify the oil. In some instances, high vaporization pressure has broken seals, evolving a leakage problem."


Perhaps that is what BMW is worried about. :dunno

Wallowa
06-08-2009, 03:38 AM
Uhhh, not always. Sometimes it is the opposite that occurs. The book "Systematic analysis of gear failures" (I love google!) states:


"Excess lubrication presents some unusual problems in a gear train. The churning effect resulting from excessive lubrication can raise ambient temperatures, because the energy involved in cutting the shear plane of the oil is reabsorbed as heat. A continual churning of the oil, along with increasing temperatures, will tend to solidify the oil. In some instances, high vaporization pressure has broken seals, evolving a leakage problem."


Perhaps that is what BMW is worried about. :dunno

Aggghhhh..how could I have overlooked the "CC" [Churning Coefficient]!

Seriously, thanks...interesting concept...always love new ideas..

"Solidify the oil" still has me scratching my head :)

GKSullivan
06-19-2009, 03:00 AM
Go over to Sport Touring and look at a similar thread there. Lots of discussion as to how that pressure may be forcing oil past the seal when the drive is hot and sucking air back in when it cools. This leads to seal failure.

Gael

TourNut
06-21-2009, 03:34 PM
Both, my '81 SilverWing and '05 Shadow Aero drool FD oil out the FD top vent the first few miles when they are ridden cold, under 40 degrees F. Go figure ?