Rear angle gearbox leak

[Ditchdablade]

Hi, I’m on a tear down off the whole rear end. The angle gearbox has had both seals changed over a year ago and it’s leaked a little ever since. It leaked before that hence the change.
I fear that I may have used the wrong oil?? I used an extreme pressure oil EP putoline. When I broke into the gearbox by removing the abs sensor I heard a hiss and that after the bike has sat for 3 days. Should there be pressure in this gearbox? Why? I fear that will just push gearbox oil through the seals. I’ve heard that some gearboxes require a relief valve for pressure. Any ideas?
I don’t want to replace the seals again and watch them blow.
All ideas welcome

 

[Andy63]

Hi Ditchdablade, Im no expert, i'm led to believe that the seals on the Final drive's usually fail because of too much oil within the drive.

BMW recommended 220ml however after seal failures it was changed to 180ml.

So you will hear recommendations of both levels on here.

I use Castrol Differential SAF-XO and always put in 180ml over 40,000 miles no issues, obviously changing it every 6000.

I use a measuring jug and an syringe to fill the Final drive to the correct amount.

 

[Mistacat]

On your previous thread you said that it was a 2006 bike, there is not a breather on this final drive , only the twin cam 2010 to 2012.
I have found it impossible to fit a breather to these earlier final drives, even with separators and the pipe exiting under the top box.
BMW had problems with seal leaks so they reduced the recommended oil quantity to 180 ml.
When I used these early final drives I fitted a breather pipe and when the final drive was hot I plugged the breather creating a vacuum in the FD when it cooled.
This should not be necessary if you stick to the later 180 ml of oil recommended, I was just playing at trying to use the original recommended quantity's .

 

[squibb34]

This is likely to get confusing, running a second thread about your drivetrain issues.

Anyway, the FD leak. Oil spec is BMW SAE75W-90 synthetic OSP gear oil, or equivalent. Putoline EP has a different spec, but I don't imagine that is the issue TBH.

Assuming the FD bearings are good & there is no axial play at the rear wheel, I suspect this may just be a blocked breather, part #22 here: -

....... https://www.realoem.com/bmw/enUS/sh...25-BMW-R_1200_GS_04_0307,0317_&diagId=33_1772

You will be aware that the FD gets pretty warm after a ride, so the unit needs to breath.

 

[mikeyboy]

This is likely to get confusing, running a second thread about your drivetrain issues.

Anyway, the FD leak. Oil spec is BMW SAE75W-90 synthetic OSP gear oil, or equivalent. Putoline EP has a different spec, but I don't imagine that is the issue TBH.

Assuming the FD bearings are good & there is no axial play at the rear wheel, I suspect this may just be a blocked breather, part #22 here: -

....... https://www.realoem.com/bmw/enUS/sh...25-BMW-R_1200_GS_04_0307,0317_&diagId=33_1772

You will be aware that the FD gets pretty warm after a ride, so the unit needs to breath.

That’s the later type fd with a breather.
The OP ‘s bike is earlier with no breather fitted

 

[squibb34]

That’s the later type fd with a breather.
The OP ‘s bike is earlier with no breather fitted

My bad - I thought it changed for the 2006 build, ie post 9/2005.

 

[Ditchdablade]

I was thinking yay it has a breather and blocked. I’ll check it tonight but I suspect not.
I checked the oil and I have a firm belief that this may be the problem. It’s a “heavy” oil incorrect obviously. Huge difference in pressure frying the light oil. So I’ll tear it down , clean and reassemble with current spec. I’ve used heavy oil before, not in a Booker I may add, extremely thick and sticks to everything. I’ll measure it out perfectly and check again.

The “hiss” definitely is a real pointer for me. It was outline heavy 80w-90.

 

[mikeyboy]

I was thinking yay it has a breather and blocked. I’ll check it tonight but I suspect not.
I checked the oil and I have a firm belief that this may be the problem. It’s a “heavy” oil incorrect obviously. Huge difference in pressure frying the light oil. So I’ll tear it down , clean and reassemble with current spec. I’ve used heavy oil before, not in a Booker I may add, extremely thick and sticks to everything. I’ll measure it out perfectly and check again.

The “hiss” definitely is a real pointer for me. It was outline heavy 80w-90.

I’m interested in why you feel the viscosity of the oil has any bearing on things?
I have regularly used 85/140 oil in these units with no problems of leakage,
It’s a sealed unit and as such will have pressure fluctuations ,this is normally noticed as misting from the RH seal,
Mainly when hot and at altitude,
,I’ve lost track of the number of phone calls I’ve received from bikermates at the top of some mountain pass in the alps
It’s normal to get a hiss/pop when the speed sensor is removed.
Personally I recommend 200ml of oil,and have been doing so for the last 16 years.