Final Drive Leak or Over flow?

[79beem]

My 79 R65 final drive has started looseing/leaking a noticeable amount gear oil from a small hole below the axle nut on the right hand side.

The lower half of the final drive is covered in oil fanning out from the small hole.

The oil runs down the outside of the final drive only whilst riding and onto the tyre .

I cant find any reference to this hole in my clymer manual.

The oil level in the final drive is currently about 5mm below the bottom thread of the filler plug hole, which is lower than the recomended level.

The leaking started when the levels were at specified levels, it seems to be getting worse.

The oil is dirty and needs changing.

Is this small hole an overflow or something else  :-/?  

[Barry]

Is this small hole an overflow or something else

Not had this personally but it's not an overflow. I believe it's designed to tell you that you have an leaking seal. Someone else will have been there and done that and will be able to tell you how to replace the seal.

[Semper Gumby]

The small hole is at the bottom of the "round" rear ends.  Part of my maintenance schedule is to run a drill bit up this hole and make sure it is clear.  The reason that it is there is to allow leaking final drive oil a place to go before it piles up and contaminates the rear brake shoes.  So this bad thing is actually a good design.  Soo.....

Your final drive seal is leaking and needs to be replaced.  These seals usually last a long time.  You can damage the seal and your final drive gears by packing too much grease onto the splines.  When you put the rear wheel on, the wheel coupler squeegees the grease up against the seal forcing grease and dirt throughthe seal into the final drive oil.  If the oil is black then you have probably contaminated the final drive oil with grease.

You can try to cleaning out the grease packed in against the seal and clean the splines and change the oil in the final drive and see if the leak stops.

I usually clean the spline on the final drive and grease the wheel coupler to keep this from happening.  I used a small flat tip screw driver to get the grease off the seal.  Take your time, be gentle.

One other possiblilty is that the rear brake arm has seals on it and they may be leaking.  I don't think this is the problem as you say the grease is contaminated.  But when you pull off the rear wheel you might look at where the final drive oil is leaking from.  I know this is a problem on the post 1980 "square" rear ends but not so sure on the "round" rear ends (pre 09/1980).

Good luck.

[nhmaf]

+1 what Bill said.    If you need to replace the large seal which goes around the spline hub in teh final drive, you need to go very slowly/carefully and/or wrap some layers of tape around the splines to keep the edges from cutting into the new seal as you work it into place.

[79beem]

By final drive seal I'am assuming you guys mean the oil seal (part 33) in figure 117 page 567 third edition. Which is situated between the shim and gasket behind the housing cover, as shown in the exploded diagram in the clymer manual?

My manual states the need for specialised BMW tools  33 1 600 to secure the final drive unit, BMW assembly tool 33 1 000 to protect the ring gear oil seal and BMW seal driver 33 1 850 and 00 5 500.to tap the new seal into the case.
 
Does anyone know if i can do the job without these tools or if there is an alternative?

The diagrams show and list oil seals but the wording in the procedure talks about a ring gear seal, is this one and the same part and is this the suspect part possibly responsible for the leak?

[79beem]

Also, if the oil levels are checked and maintained am i able to continue riding until i have the parts and tools or should i take her of the road?  

[Semper Gumby]

As long as that little drain hole in the bottom of the final drive does not get clogged and the leaking oil can get out you are OK.  But there is always a chance that the oil will somehow splash onto the rear brake shoes.  It's not a disaster, just an issue.  (You will have to buy new rear brake shoes early).  And yes keep checking the oil level.

Good luck and good hunting.

[Bob_Roller]

You can replace the final drive output seal without any special tools .

You need  heavy tape to put over the final drive splines when you reinstall the cover, so you don't cut the seal .

[Julio A.]

Based on my experience, it is also quite a feat to remove the leaking seal without destroying it. Although it is already leaking, so there's no point trying to preserve it.

It is still runnable, given the fact that you constantly top up the oil levels.
Eventually, the oil will find it's way to the rear brake and a new brake shoe is in order.

I had no special tools to work it with before, so I removed the whole rear hub from the bike and had a machine shop install a new oil seal.

And I did cut the oil seal in my first attempt. I never did though of putting tape to cover those splines.
Luckily, the oil seal found in a Mitsubishi heavy duty engine truck fits the R65. So multiple attempts were possible.

[Vegasrandall]

So what's the mitsubishi part number? Is it cheaper/ better than the BMW part?

[Semper Gumby]

Make sure you soak the seal in final drive oil for 2 hours before installing.

Misubishi?

[Julio A.]

Make sure you soak the seal in final drive oil for 2 hours before installing.

Uhhh..... am I supposed to do that?  
If so, nope, I did not.

Imagine the surprise of the hardware store guy that gave that oil seal to me. He ask what vehicle I will use if for. When I replied for a motorcycle he said that It was meant for a truck.

It does not have the exact dimensions as the original part, especially the rubber part, the one I installed seemed a little more narrower in that part. But it fits; It does not leak.

I don't know how much the OEM costs but the mitsubishi oil seal cost me 250 pesos. Around 5 USD.

Yes, it's Mitsubishi.  

[Semper Gumby]

It just softens the lip.  Makes it seal better.  If yours doesn't leak then hurray!

[Teo]

It sounds to me that the leak is coming from the weep hole outside the final drive housing and underneath the axle hole.  That indicates a leaking seal behind the needle bearing inside the final drive.  The final drive will need to be disassembled, taking out the ring gear to get to the needle bearing.  Be sure to note the position of the spacer/shim in relation to the ring gear and the housing when you pull off teh cover.  The housing around the bearing will need to be heated up (til spit sizzles) and the bearing will drop out.  Then the inner seal can be replaced. I would also replace the large seal on the housing by the splines.

Continuing the conversation from some of the other posts, the large seal on the inside of the drive, behind the splines can be replaced very easily even with the final drive in place on the bike.

Depending on the year of the R65 as well as /5s, /6s and /7s, there will be a drain hole in the lip projecting out a little from where the large seal seats or there will be nothing.  I use a pipe cleaner to punch that hole since it takes a turn up inside. My '82 LS has no lip so any leakage will go directly onto the splines and brake.

The other thing to check is the brake actuating shaft that passes through the final drive housing.  The older final drives have a sealed tube for that brake shaft to pass through.  The later ones ('82 R65LS and other models) have three "O" rings on that shaft.  The "O" rings will harden and allow rear-end fluid to leak either outside or inside. Bummer design.

[79beem]

so its been a few wks since i found the leaky final drive, i've been checking + topping up the levels before + after each ride. The final drive level seems 2 take a while 2 drop but i've noticed recently that the drive shaft levels are constantly dropping.. Could this be the source of the leaky fluid? if so, is that still the output seal that needs replacing?