Rear differential service tip !

[gdouglas]

I had to replace my leaking right hand differential seal on my RT the other day, which was a pretty easy job by itself. Of course, not knowing how much gear oil had actually leaked out past the bad seal, the only way to know for sure how much oil is actually in the differential is to drain completely and refill with the repair manual specified 230ml of lube.

 

We all know what a PITA it is to fill the differential through the speed sensor hole as the repair manual states. So I decided to see where in fact the actual level of 230ml of oil capacity was in relation to the "drain" plug hole. With the bike on the centerstand, I then put 230ml of lube in through the speed sensor hole and pulled the "drain" plug out for a level inspection. What I found is that the level was within about a 1/16 of an inch from the bottom of the "drain" hole.

 

Judging by this experiment, we can now in confidence use the bottom edge of the "drain" plug hole as an actual fill level and forget about the hassle of measuring out the actual 230ml and trying to get it all through that little speed sensor hole.

 

Why the BMW repair manual doesn't tell us this is beyond me. BMW has us going around our elbows to get to our behinds for what should be such a simple task.

 

I hope this tip helps a lot of you for your future differential servicing needs.

[hopz]

Thanks for the tip. A true time saver. Now we just need to reconcile your data with the conventional wisdom that 230ml is above the drain plug, if of course, you have a drain plug... which I do not.

[Joe_C]

Has anyone tried putting 230-240 ml in through the side "drain" plug to see if it's at the bottom of the opening?

[bobbybob]

Has anyone tried putting 230-240 ml in through the side "drain" plug to see if it's at the bottom of the opening?

 

Yeh, that should be done just to insure something else isn't coming into play using the speed sensor hole. However, even if the drain plug fill method still wont quite take the full 230ml, it seems that doing something with the bike's angle (temporarily lower the front or raise the rear) would add just enough "slant" to the drive so the full amount would be accepted thru the drain plug....or even put the bike on a downhill slant (careful with that center stand)....

 

However, I would not use "the bottom of the drain hole as a fill point" because that point could change depending on the slant of the bike (floor not level?). I would stick to the ml quantity.

[RoSPA_man]

Has anyone tried putting 230-240 ml in through the side "drain" plug to see if it's at the bottom of the opening?

 

Yeh, that should be done just to insure something else isn't coming into play using the speed sensor hole. However, even if the drain plug fill method still wont quite take the full 230ml, it seems that doing something with the bike's angle (temporarily lower the front or raise the rear) would add just enough "slant" to the drive so the full amount would be accepted thru the drain plug....or even put the bike on a downhill slant (careful with that center stand)....

 

However, I would not use "the bottom of the drain hole as a fill point" because that point could change depending on the slant of the bike (floor not level?). I would stick to the ml quantity.

On a related topic, I want to lube my spline (sounds rude. Must I remove the speed sensor in order to tilt the FD to release the spline or can the speed sensor wire be disconnected up along the line somewhere? If I do have to remove the speed sensor, would some duct tape or similar seal the hole well enough temporarily to avoid any possible leakage when I drop the FD at 90degrees? (I do not need to change the FD oil)

[medic319]

If the drive fluid does not need changed, then I would think that the spline lube would still be ok. I would just do both together, and there is no great cost in changing the fluid. The other thing you could do is get an assistant to hold their finger over the speed sensor hole while you lube the splines. Duct tape may or may not hold. I would hate to see you drop the drive, lose a bunch of fluid, then not have any on hand to refill it.

[BeemerLover]

Gdouglas,

 

While on the centerstand was the front wheel resting on the pavement when you measured the level through the rear drain plug? Were you on reasonably level ground?

 

Gael

[IanW]

I had to replace my leaking right hand differential seal on my RT the other day, which was a pretty easy job by itself. Of course, not knowing how much gear oil had actually leaked out past the bad seal, the only way to know for sure how much oil is actually in the differential is to drain completely and refill with the repair manual specified 230ml of lube.

 

We all know what a PITA it is to fill the differential through the speed sensor hole as the repair manual states. So I decided to see where in fact the actual level of 230ml of oil capacity was in relation to the "drain" plug hole. With the bike on the centerstand, I then put 230ml of lube in through the speed sensor hole and pulled the "drain" plug out for a level inspection. What I found is that the level was within about a 1/16 of an inch from the bottom of the "drain" hole.

 

Judging by this experiment, we can now in confidence use the bottom edge of the "drain" plug hole as an actual fill level and forget about the hassle of measuring out the actual 230ml and trying to get it all through that little speed sensor hole.

 

Why the BMW repair manual doesn't tell us this is beyond me. BMW has us going around our elbows to get to our behinds for what should be such a simple task.

 

I hope this tip helps a lot of you for your future differential servicing needs.

 

The BMW repair manual does not tell us this because with 230ml of oil in the FD it is above the level of the drain plug. When I removed the plug oil came out that is why filling from this plug is a no go.

Ian

[Ken H.]

Slight caution is in order here though as the location of the drain plug has changed on various models and years of the R1200xx series.

 

Best still to measure out 230ml IMHO.

[bobbybob]

Has anyone tried putting 230-240 ml in through the side "drain" plug to see if it's at the bottom of the opening?

 

Yeh, that should be done just to insure something else isn't coming into play using the speed sensor hole. However, even if the drain plug fill method still wont quite take the full 230ml, it seems that doing something with the bike's angle (temporarily lower the front or raise the rear) would add just enough "slant" to the drive so the full amount would be accepted thru the drain plug....or even put the bike on a downhill slant (careful with that center stand)....

 

However, I would not use "the bottom of the drain hole as a fill point" because that point could change depending on the slant of the bike (floor not level?). I would stick to the ml quantity.

On a related topic, I want to lube my spline (sounds rude. Must I remove the speed sensor in order to tilt the FD to release the spline or can the speed sensor wire be disconnected up along the line somewhere? If I do have to remove the speed sensor, would some duct tape or similar seal the hole well enough temporarily to avoid any possible leakage when I drop the FD at 90degrees? (I do not need to change the FD oil)

 

 

I thought you could either disconnect the speed sensor wire, or else the clips that hold the wire, freeing up some slack. Maybe i'm wrong...

[gdouglas]

BeemerLover,

 

When I did all this filling and measuring, my bike was on the centerstand with the front wheel on the floor. For the record, my bike is a 2005 model....just in case my drain plug location is at a different height than later years as mentioned in an earlier reply.

 

By the way, for what its worth, when I drain the differential, I let it drain for about 20-30 minutes. I am not sure if varying the draining time duration has any effect on fill level when filling by volume only.

[rew(r1200st)]

how did you get the old seal out

[Jim VonBaden]

There are far to many variables here to use this as a standard. Bike loading, shock settings, level of fround and bike type all make a difference.

 

For example. My R1200GS on the CS with the front tire down and on level ground when I pull the drain plug fluid will run out of the drain, 9:00 drain on my 05. I have seen this on most of the R1200 final drive services I have done, over 20 different bikes.

 

I highly recommend you fill based on volume, 220ml-230ml.

 

I do, however, add 180ml to the drain plug, plug it, and add the rest in the sensor hole. It is much quicker.

 

Jim

[BucksTherapy]

Slight caution is in order here though as the location of the drain plug has changed on various models and years of the R1200xx series.

 

Best still to measure out 230ml IMHO.

 

Absolutely! I am one of the lucky folks that had a failure on my 06 with the drain plug in the side. It used to take 230ml which would overflow the plug in the side but but not the ABS Sensor plug hole.

 

My new diff has the drain plug in the bottom(Yes!)and the abs sensor hole seems lower in the back. If I put 240ml in the abs sensor hole on this diff it overflows. Called BMW dealer to see if there is a new spec. They looked it up and tell me 220ml. This seems right as 230-240 overflows the ABS sensor hole with bike on center stand on level floor with front wheel touching the ground.

 

I think I have about 230 in the diff now. Would 10ml over the new spec matter?

[Jim VonBaden]

Slight caution is in order here though as the location of the drain plug has changed on various models and years of the R1200xx series.

 

Best still to measure out 230ml IMHO.

 

Absolutely! I am one of the lucky folks that had a failure on my 06 with the drain plug in the side. It used to take 230ml which would overflow the plug in the side but but not the ABS Sensor plug hole.

 

My new diff has the drain plug in the bottom(Yes!)and the abs sensor hole seems lower in the back. If I put 240ml in the abs sensor hole on this diff it overflows. Called BMW dealer to see if there is a new spec. They looked it up and tell me 220ml. This seems right as 230-240 overflows the ABS sensor hole with bike on center stand on level floor with front wheel touching the ground.

 

I think I have about 230 in the diff now. Would 10ml over the new spec matter?

 

I said 220-230 above, but I always error on the low side. 230 will probably be fine, but since the FD is not vented, a tiny bit less is better IMHO!

 

Jim

[BucksTherapy]

Slight caution is in order here though as the location of the drain plug has changed on various models and years of the R1200xx series.

 

Best still to measure out 230ml IMHO.

 

Absolutely! I am one of the lucky folks that had a failure on my 06 with the drain plug in the side. It used to take 230ml which would overflow the plug in the side but but not the ABS Sensor plug hole.

 

My new diff has the drain plug in the bottom(Yes!)and the abs sensor hole seems lower in the back. If I put 240ml in the abs sensor hole on this diff it overflows. Called BMW dealer to see if there is a new spec. They looked it up and tell me 220ml. This seems right as 230-240 overflows the ABS sensor hole with bike on center stand on level floor with front wheel touching the ground.

 

I think I have about 230 in the diff now. Would 10ml over the new spec matter?

 

I said 220-230 above, but I always error on the low side. 230 will probably be fine, but since the FD is not vented, a tiny bit less is better IMHO!

 

Jim

 

Thanks Jim, This sounds liks good advice. Looks like I will be draining and refilling again b4 my upcoming trip.

[gdouglas]

rew(1200ST),

 

It isn't that hard to get the old seal out. You first take a small screwdriver to pry the seal cover off by prying against the ID of it. Behind this cosmetic cover, you will then see a snap ring that you can get out with a scribe. Next is the seal. You have to center punch a nice mark in the metal jacket of the seal so that you can drill a 1/8" hole to start a sheet metal screw into. Be careful or use a drill stop so that you won't bump the bearing that is behind the seal. Once you thread a sheet metal screw into the hole you just drilled, take a pair of diagonal cutters to grip the screw shank and pry the old seal out. Tap the new seal in very carefully by walking a 1/4" flat punch around the face of the seal until seated so that you can put the snap ring back in. The seal cover just snaps back on and you are done except for refilling with lube.

[Anton Largiader]

Interesting. On the 2005 RT I have on the lift, 230ml just barely begins to ooze out of the drain hole. I put all of the oil in that way.

 

On other bikes I know oil has come out when I remove the drain plug, but I never measured how much was in there.

 

A bit easier to fill that way.

[BeemerLover]

For what it is worth, a trusted BMW 'rench indicated to me that the sealed rear differential is prone to leaking as there is nowhere for the oil to go as it expands due to heat. That was why the old ones had a vent. He said it doesn't take much pressure to force a little bit of oil past the seal and the leak multiplies with additional heat/cool cycles.

 

Gael