Rear Wheel
Splines; Rear Drive Oil Leaks, Replacing a Rear Drive Left Seal,
Inner seal, Nose seal, Oil Leaks and Drum Brakes, ETC.
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rearwhlsplines.htm-45
NOTE!!!!...this article also covers airhead models withOUT rear splines!!
note: some things in the following article are repeated in more than one place, and said somewhat differently to promote clarity. This is intentional...and please read this entire article before working on your rear drive.
I. SPLINES (applicable to TWIN shock models only):
Questions arise now and then about just when, how, etc., to overhaul the rear wheel splines, when to clean and re-grease, ETC. The rear wheel itself contains a splined cup that is, when stock, riveted to the wheel. Rear Wheel Splines, in this article, refer to both that wheel cup, AND to the driving mating splines, which are part of the Rear Drive....and those splines on the Rear Drive are on the left side of the Rear Drive, and are part of what is called a Crown Wheel. In car terminology, it is the ring gear.
WHY do splines wear?
Splines wear due to quite a few different things going on, and I
see little need to discuss the finer metalurgical details, except
to mention that RUSTING from failure to grease regularly,
together with impact forces of various types, maybe some
fretting, etc., are causes. The rear wheel cup splines should be
cleaned and re-greased at EVERY tire change.
Being anal, I also clean the wheel bearings, oil them, install
without seals, and measure the preload, adjusting if
need-be. Then, I balance the tire/wheel; then, I clean off
the oil, grease the bearings, renew seals, and ride until the
next tire change.
>> If you have a Monolever or Paralever bike, you do NOT have these splines! These splines are on the two-sided rear suspension models ONLY.
HINT:
It is probably best to clean and grease only the WHEEL
cup splines, and NOT the drive splines. That will tend to
help avoid pushing any gritty matter, no matter how slight, into
the left side of the rear drive large oil seal, which tends to
make it leak. AVOID any brush bristles being left in the spline
area, especially in that seal!...the seal will be injured, and
will leak oil, which will probably come out the hole at the
bottom of the drive near the drain hole....the
later airheads do not have that drain hole, the left side of the
rear drive is a bit different, not having a sort-of 'collector
cup'.
The rear drive splines
generally wear at a different pace, than the mating rear wheel
cup splines. When you remove the rear wheel, it is
easy to eye-ball both splines. These straight-cut, square outer
edged teeth last a long time, but this depends on
maintenance....and how ridden. If you do not grease them
regularly, they tend to wear fast, and some of that wear is from
rusting. If you pull a trailer or make jack rabbit
takeoffs, shift jerkily, etc... they wear faster. It is NOT
unheard of for trailer pullers to get only 30K out of these
splines. PROPERLY driven and maintained, a bike with
a trailer or sidecar can have these splines last vastly longer
than that!
Some rebuilt splines may last longer than the original material. It is a specialists job to rebuild splines, which is often done as opposed to purchasing a brand-new gear set...brand new gear sets are very pricey, and you can add a fair amount labor to shim a new gear set. That is why rebuilding is MUCH cheaper. In the rebuilding process, the crown wheel is rebuilt, and the wheel cup unit with its splines is replaced if worn considerably.
As a GENERAL rule, if the outer edge portion of the drive splines teeth still have SOME squareness to them; that is, they have not gone to totally pointy, the bike will be unlikely to have a rear drive failure UNLESS you are pulling a trailer or otherwise being hard on the splines.
Once
totally pointy, with NO square outer edge, you are on borrowed
time indeed. My personal rule of thumb is that when
the spline has worn so that a little less than 1/3 of the
original outer flat edge is left, it is time for rebuilding the
splines of the drive, (and quite possibly time for a new rear
wheel cup, or to watch it all very carefully from then on). It is
generally a poor idea to rebuild JUST the rear drive's splines,
without the wheel cup spline also being replaced, but many a
person has done this successfully. It depends on the
amount of wear. Quite often the rear wheel cup splines are
hardly worn. Doing only the drive spline rebuilding MAY
accelerate the wear ...that is...the wear may be faster than with
the wheel cup being replaced, but I have no direct proof,
although I DO believe it.
Certainly, eventually the rear wheel cup splines will need
replacing...these are replaced, NOT rebuilt. It is a
specialists job to re-rivet these cups; but, bolts, if done with
correct parts, can work quite nicely.
Most will...OR SHOULD.... simply remove the
rear drive and send the rear drive and
wheel to someone like Hansen's in Medford, Oregon, for a rebuild.
This is a specialist's job....for a special machinist....with
vast experience. Hansen's machinist uses a
special welding rod, same as used by Caterpillar, and then
re-machines the spline. It is CRITICAL that the
assembly remain undistorted and concentric....that is not usually
the case with inferior rebuilds. Installing a new riveted
wheel cup is also generally not a job for most home mechanics,
although with a big enough press you can do it. Hansen's
knows how to do it correctly. For most other folks,
riveting is questionable, perhaps, and it would likely be better
using bolts. I can argue on both sides of the
rivets-bolts question, but quality grade 8.8 bolts could be used,
and may be better than rivets, if installed
correctly. 1/4-28 special shouldered bolts are used,
you can contact Oak Okleshen about those shoulder
bolts;....or, send the wheel to Hansens and they will
properly re-rivet the new cup. I have personally
spoken with Craig Hansen, and I approve of their repair
methods. Hansen's will accept just the outer cover
assembly, but I truly think it best to send the entire
drive....they can fix anything they find wrong, and you can so
inform them to do it. You will not then have to play with
new seals, etc. I also approve of Oak's bolt
method. Oak also designed and built a very VERY
robust, non-wearing, rear drive conversion, for his own airhead,
that pulls a trailer. You can ask him about it....but don't
expect him...or anyone...to build you such a very pricey
conversion.
**********************************************************************************************
WHEEL
cup replacement:
***NOTE: The /5 used 5 mm and not 6 mm rivets. The same modification METHOD will work. Specific technical details for the /5 will be posted here as soon as I have them.
The BMW rivets are a mild steel, and work under SHEAR....they
stop the hub from rotating because of the tight fit. The
riveting method is a tad special, but that is not of concern
here. The holes in the spline and hub are almost exactly
0.250". Installing new rivets is not as easy as
it may sound. If you are doing this job yourself, you
may well want to use bolts. I suggest
"close-tolerance" bolts that you specially
order. That means that the UNthreaded portion
of the bolt shank is held to about a .001"
tolerance. NO thread must be in the hub holes...you
want a SHOULDER BOLT of the correct sizing. You could stack
washers if need be. Otherwise, the threads WILL eat the
hub. A hardened washer is used under the
nut. One method of doing this job is to machine
the hub so the surface where the nut is going to be is parallel
to the mating surface of the hub. The surface comes curved,
which is why you do this. Use a 0.25" hand reamer if
you have to, to get perfect holes. Chamfer the hole on the
outside of the hub to give clearance for the radius'd portion of
the bolt head, where it joins the shank. If things fit
correctly, they will be quite tight and you probably will need a
soft-faced hammer to get the bolts to fit. Seal the
threads with Loctite Blue. Cut off the excessive
threads, and clean them up.
One Airhead reported using 1/4-28
thread size:
Mil-Spec 12 point close tolerance bolts, cad plated,
MS21250-04012
MS20002C4...washers, countersunk on one side as the bolts are
radiused under the heads...and you need to grind one side so as
to fit under the nut on the spline cup.
MS21042-04 self-locking nuts (add Loctite anyway).
NOTE: Aircraft AN-174-12 will probably work as well as will
NAS6204-13 for bolts. Try an aircraft parts
supply. A good source for these items at a GOOD price
is Aircraft Spruce & Supply....which has the close tolerance
AN174-12 bolts. www.aircraftspruce.com
For nuts, you could also use AN365-428A or AN364-428A.
This AN364- number are half-height.
If your holes were already
elongated, you could drill oversized and use the next sized bolt.
Here is the method that OAK (askoak@aol.com),
a recognized authority, recommends for cup replacement:
1. Dimple each rivet on the inside of the wheel in the
exact center using a center-punch.
2. Use a drill of about 1/8" diameter and drill
straight down about half an inch or so from the surface. Do
not allow the drill to break.
3. Enlarge the center hole to about 3/16" diameter
with a larger drill bit.
4. Using a CARBIDE tipped masonry drill of about 3/8"
diameter, drill off the rivet mushroomed portion. You will
suddenly hit the hard surface of the wheel cup...be careful not
to ruin the carbide drill bit. STOP when the mushroomed
head is drilled-off.
5. Use a pin punch and tap out the rivet core towards the
outside of the wheel.
6. Lift out the wheel cup. Get the new one ready to
mount.
7. Get 10 each allenhead cap screws, plated or stainless,
with nuts, all sized 1/4-28. Purchase these about 1-1/2 to
2 inches long...so you have about 1/2 inch of UNthreaded shank
below the allenhead.
8. Trim the length from under the head to the end, to about
15/16". Put a wave washer under the head of the bolt,
insert bolt from outside of the wheel, through the hub, then
through the new wheel cup.
9. The nuts for the bolts will NOT QUITE fit properly onto
the wheel cup and will want to slant slightly...which is NOT
ALLOWABLE! So, grind part of the nut away that sits against
the wheel cup, so it lays flat, when you run the bolt through
it. This can be done on a belt sander and screw two nuts on
a long bolt locked together so they do not spin and grint the
outermost nut to the correct contour. You won't burn your
fingers this way...keep water available in a small bowl...keep
the parts cool.
10. When ready to install the nuts, be sure all 10 bolts
are in place. Use blue Loctite. Do one nut, then the opposing
nut, do at 90 degrees, and continue evenly, drawing things
up. BE SURE that the side of the nuts you radiused,
face the wheel cup radius. The
tops of the bolts on the inside should be even with the top of
the nuts, after all is tightened. If too long, fix
that...otherwise the bolts may hit the casting on the rear drive.
MY comments:
I prefer the aircraft bolts and more precision assembly. When
done, it is much stronger than the original stock
item.
For most folks, you are probably better off sending the entire
drive (and wheel), but I can't make a blanket 'for sure'
statement here. It is NOT difficult to simply remove the crown
gear and cover plate (cardan cover) from the rear drive. I
have posted at times the procedure on how to replace the large
left side seal (heating required, shim to protect seal required,
etc.), and you would incorporate that procedure. Be
SURE to refer to a proper procedure if you intend to disassemble
your rear drive. You may find the hardest part is cleaning off
the old gasket. I am NOT kidding...it can be a PIA. If you
send off the entire rear end it will cost more, but may well be
worth it to you.
HINTS: When re-installing the rear drive on twin shock models, do NOT tighten the 4 nuts that hold the drive assembly to the driveshaft tube, unless the axle is in place (neither left side axle clamp bolt nor axle nut need be tightened at that point of procedure). Having the axle in place aligns the rear drive to the swing arm. This will avoid any possible slight misalignment that could soon ruin the rear drive bearings.
On all models, do NOT
use a sealant, just the stock BMW gasket, at the
cleaned joint between rear drive and the driveshaft housing, be
sure that there is no metal proud of the surface.....the rear
drive and driveshaft housing flange MUST be flat and seal to each
other withOUT any gooping.
Grease types: I have tried a number of greases. The
problem is that no grease seems perfect. On the one hand,
you want a grease that allows the wheel to be pulled off the
drive splines...and any tar-like grease that would be ideal for
this purpose, would make that almost impossible, especially if it
is cold. On the other hand, you want a grease with great
moisture resistance and that resists impact effects. As
opposed to the transmission input splines, there is almost
zero wiping motion in the direction of the splines teeth
(horizontally), but far higher forces to try to squeeze out the
grease from the teeth itself.
I have tried outboard marine type drive greases, Chevron red grease EP Ultra Duty NLG1 or NLG2, moly greases, etc. All these work adequately, especially with some added moly.
At the present moment I am doing long term tests on the following for clutch splines, and will also for the rear splines:
Würth #SIG3000...[phone 800-346-4198].
NOTE: Honda makes a Moly 60 grease, available at their motorcycle dealerships, with a high moly content. Folks have used this by itself, with good results.
II. Oil Leaks from REAR DRUM BRAKES models:
In 1985 BMW changed the
design of the rear drive, where the brake actuating rod
passes. In the new design, the rod passes
through a tube, no O-rings are needed, but you have to grease the
shaft. I recommend a new O-ring (s), if an older version,
and shaft greasing of both, at every tire change. The tube
can be added to earlier models. REFER to the BRAKES
article (that is a hyperlink to the article) beginning area for
MORE information. NOTE that on the 1981-1984 rear ends with
that tube installed, the tube has to be aligned by inserting some
sort of shaft, such as modifying an old /5 front axle. If
the cover is not correctly aligned, the shaft will LEAK
oil!!...no matter the O-rings! There is a LOT
of confusion with trying to update a rear drum brake actuating
camshaft, this is the shaft that has one or more O-rings. I
use silicon grease on the O-rings, but common petroleum grease is
also fine. The early and later shafts are different, with
different grooves and spacings between grooves, for the up-to 4
O-rings. Trying to order the correct one may be an exercise
in frustration, and there is nothing wrong with using your old
stock shaft.
Shaft's had 4 O-rings in the square grooves. Sometime
around 1983 BMW modified the shafts, went to shallower grooves,
and different spacing on them. It is all very confusing,
especially if trying to update.
NOTE: A drum brake model rear drive will fit with little effort, onto a disc brake model bike.
NOTE: Very early snowflake rear wheels have casting nubs in the large dished right side, and those must be ground off, if fitting to a rear end that is of later construction, or the wheel will freeze against the bolts holding the drive cover.
HINT: Rear
drive drain plugs and crush washers are available in
oversizes. The oversize 16 x 20 washer is 07-11-9-963-259;
and the oversize plug is 11-13-0-007-162.
BMW does not, to my knowledge, offer an oversize plug to fit the
driveshaft DRAIN ....which is LOCATED on the rear drive....but
there are aftermarket larger plugs. Fixing bad
DRIVESHAFT drain threads is a bit of a job due to the disassembly
required.
If
oil is moving from the driveshaft housing and going into the rear
drive, there are a few possible causes:
1. The rear drive input nut is loose. That MUST be
corrected, immediately!...it can cause major damage to the rear
drive. Whether or not oil is migrating, if you ever have
the rear drive off the driveshaft housing, DO check that input
nut!!!
2. INPUT
SEAL AREA: AFTER the /5, the 24 mm hex
input nut presses against a large flat washer and between that
washer and the input gear, is a thick plastic 'seal', that is
designed to deform and prevent oil from migrating down the
splines into the rear drive. Those are small, and
cheap. On /5 models, and I do it to all models myself
when replacing the large blue input nose seal, I put some
Permatex Form-a-Gasket #2 (NON-hardening) on the input gear
splines...at the more forward half inch or so of those
splines. The threads of nut and shaft must be
cleaned, and Loctite BLUE used on those threads. Tighten to
about 120 footpounds!! A tool is needed to enable
tightening...or, bungee the nose of the drive to the wheel.
Ed Korn makes the tool if you absolutely must have a tool, rather
than the Airhead solution, that bungee. Ed makes two
types of tools for working on the nose area. A
tool is needed to unfasten the ring that holds the bearing/seal
in place, but you don't absolutely have to have the tool that
prevents the gears from rotating whilst R/R that input nut...you
CAN strap the nose and wheel together with a bungee.....but, if
the drive is apart, or you want something 'nicer'...the Ed Korn
tools are neat to have.
3. You might have a PLUGGED breather hole at the
speedometer bolt...enough pressure and it can force some oil past
an OK or fair condition seal....but, that normally does not
happen, as the rubber bellows at the transmission output usually
just swells.
4. Behind the input nut, input nut washer, input seal....is
a large blue conventional oil seal. That oil seal is held
in place by a 4 notched steel ring that is threaded into the
input nose area. It is common to seal these large diameter
threads with a small amount of sealant (Hylomar is best here),
but other sealants might have been used, and the ring may not
want to unscrew. HINT!!....>>HEAT the entire housing
to about 230°F....and then unscrew the ring. A special
tool is required. Ed Korn makes them, or, see your BMW
dealer. When replacing the blue seal, be careful with it,
it is a press-fit into the threaded ring (heat it a bit), and the
ring is installed, rear drive again heated, to about 85 foot
pounds. Seal the ring's threads with Hylomar or other
good sealer, and do not forget that the housing must be HOT when
tightening the ring.
If your drum brake shoes got saturated with rear end oil, you can try to clean them by soaking in a strong solvent. That sometimes will work. If the actuating shaft O-rings are NG, they must be replaced. I recommend ALWAYS replacing those O-ring seals when working on the rear drive area....and, even, with new tire changes if you are anal enough. Late tube models use grease. Early models may have up to 4 O-rings in the square grooves. See earlier in this article on some information on these confusing shafts.
III. Rear Drive OIL SEALS, twin-shock models (and applicable in many ways to the Monoshock and Paralever):
If you are leaking oil from the bottom of the
rear drive, you need to determine the source. There can be
THREE. One is the DRUM brake shaft O-ring(s) (see
above). There are two internal seals in the rear drive that
could be leaking. This means a more deeply hidden one; and,
the fairly easy to deal with large one on the LEFT
side. How to tell which? Well, it is
almost always the left one, which is exposed inside the wheel
area to dirt, improper greasing allowing dirt into the seal, etc.
(esp. twin shock models). BUT, on the OLD
bikes, there was a weep hole at TWO places,
under the boss at the axle nut area, and internally, on left side
cover. On later models, there
is only that left side cover internal weep hole, or, none.
Since the RIGHT side seal requires a more complicated disassembly
of the drive, one should hope that it is the left
seal! You can usually tell by looking at things with
#1 eyeball. The large left seal replacement is not a big
job, but must be done carefully.
You CAN leave the drive on the bike, or you can remove the drive
entirely from the driveshaft. That might well be the better
approach, as you will find the cleaning of the left cover gasket
area far easier on your workbench, and
you can then check the input nut, and you can repair any stripped
driveshaft drain bolt, ETC. NOTE that to
Helicoil a stripped driveshaft drain bolt, you need a special
tool, to remove a threaded ring from the input nose, and a method
to hold the innards from rotating for the nose
nut. ....this was mentioned earlier.
For the left seal:
First remove the wheel. If you decide to remove the drive from the bike, unbolt the drive from the driveshaft housing. You will then require a new paper gasket for the driveshaft-rear drive junction.
NOTE: when replacing a rear drive on a twin shock model, leave the 4 nuts at the driveshaft housing a bit loose, insert the axle, and THEN tighten those driveshaft housing bolts....otherwise you run the risk of a very slight misalignment, which can rapidly destroy the bearings. NO sealant at the paper gasket. DO check the tightness of the input nut, many have been found loose, and a loose nut can cause rapid failure of the drive, big $$$. NOTE: on pre-1976, use some sealant under the washer/shaft under that nut, on the splines. On models after the /5, be sure to replace the small plastic seal under the input nose nut/washer. Use Loctite BLUE on the nut threads. I use sealant on those input splines on all models, myself. 120 foot pounds, 24 mm socket.
If you have the drive OFF the bike (which is NOT mandatory for the left seal change), NOTICE that there is an internal screw-in ring with 4 notches at 90 degrees each, that is behind that input nut....and notice that if you strip the driveshaft drain hole, you can not properly repair those threads without removing that ring nut....which is also very tight....and requires a special tool. Ed Korn makes a clever one, or use your dealership. When you remove that threaded ring (which contains a large blue seal you will have to replace if the ring is removed), you must heat the rear drive.
UNfasten the left cover. You may have
nuts, not bolts. The cover may stick to its
gasket. Use the two 5 mm threaded holes provided for this
purpose, and with two 5 mm bolts screwing in those bolts will
force the cover off easily.
The cover will remove with the crown gear, spacer, bearing, all
as a unit. It is CRITICAL that you remove every last
remnant of old paper gasket...NEVER damaging the surfaces, as NO
sealant is used! You must NOT use a sealant! YOU
MUST use a NEW
paper gasket when reinstalling the cover, again...you can
NOT use sealant!!! The paper gasket
is a KNOWN THICKNESS which affects gear mesh!
NOTE!!!......BMW is reportedly shipping a different thickness of paper gasket, than originally installed, for the left side large cover. Using a different cover gasket thickness will necessitate reshimming the rear drive...not generally a layperson's job! Try to find the original thickness of gasket! Use NO sealant!!!!
NOTE: BMW did a few rear drives without a paper gasket, using a sealant. If you add a paper gasket, you will upset the gear mesh tolerances ("shimming").
As
a general rule, BMW uses no sealants on the airheads, except at
the cylinder bases. There is NO sealant used at the
interface of rear drive and driveshaft housing.
Before doing the next step, eyeball the seal depth and remember
it.
Use an oven (or a
mild and broad flame), and heat the cover assembly which
is now off the drive of course, gently, in a circle pattern, and
when the cover is approximately at the point of water sizzle
(200°F+-), the entire crown gear, etc., will drop out of
it. This exposes the hidden bearing. The shim is
exposed too...do NOT forget about that shim!! If you have a
drum brake rear drive, don't forget about the O-ring on the
actuating shaft (only the very late drum brake productions had no
O-rings, only a tube, and grease was used on the shaft, and one
had to install the cover carefully in alignment). See brakes
article, and information here, earlier.
Use gloves, it is HOT! The seal is, of course, right
there in front of you. You DID NOTE its direction, spring
inwards....and its depth?
HINT: some folks use their oven, some use a hotplate with a metal sheet on top to spread the heat. Use of any mild flame must be done VERY cautiously, spreading the heat;....I recommend against that unless you are very careful.
I like to clean up the surface of the crown gear that the seal rides on (where seal does its sealing). I do this with quite a few minutes of work with a strip of crocus cloth. Do not even think about using sandpaper, etc. of coarse grit. 1500 or 1600 silicon carbide paper and kerosene as medium is OK, but be awful careful, and finish EXTENSIVELY with crocus. Do NOT use even 1500 if finish irregularity can't be felt with fingernail...(although you can SEE discoloration)...for no-feel finish, avoid the 1500 and USE crocus cloth! You will generally only find 1500 or 1600 grade, and crocus, at an autoparts store or hardware store that deals in fine quality paints, car paints for instance, or a tools supply store. Do a very thorough cleaning job, leave NO remnants of these cloths, grit, etc. I want to make this very clear....if your fingernail does NOT feel anything on the seal contacting area, use only crocus cloth. I use the crocus cloth (and/or 1500) with kerosene as a medium, and between thumb and forefinger.
Note: the new seal will bed itself to this smooth discolored area. If the area is roughened by use of a coarse sandpaper, the seal will NOT SEAL, or will be soon destroyed. The finish must be SMOOTH...like glass!...to the feel. In MOST instances, the surface is fine, as is, although some crocus cloth work will ensure a positive oil sealing.
The new seal must be installed squarely, and best
at the correct depth. If you cannot figure that
out, you can have a shop do it with the factory tool
33-1-860...and they maybe also have the tool for protecting the
seal too, 33-1-800. I have never had a problem
doing the seal depth by eyeball, and making a seal protector is
easy: (pay attention here!!)::
When reassembling the crown gear wheel, you
must protect the new seal from being damaged by the spline
teeth. Make up something with old shim metal, or something
from a tin can, or stiff but thin paper. Do
NOT nick the seal sharp edge (the working edge that is) in the
slightest...or you have wasted ALL this effort. That
seal LIP is critical to be UNinjured. Reheat
the cover before refitting the ring/crown gear and bearing...do
NOT forget that shim!! Do NOT follow any advice that
says to do things differently. The crown gear and shim
and bearing must all go fully into the cover...which it will,
EASILY...to full depth...if the cover is HOT.
Let the drive cool off...then clean the bearing, cover, etc;
then...OIL the bearing, all over.
After the paper gasket surfaces are 100.000% cleaned of old paper gasket, and not nicked, and cleaned, you install a new paper gasket, NO sealant, and bring the bolts (nuts) up EVENLY, criss-cross, and ending at 13-15 foot pounds on the 13 mm heads...
btw...the specification for the cover, called a
Cardan cover, is 20 Nm, or 15 ftlbs.
Be careful about the oil inspection hole plug...that horizontal
rear facing threaded plug and washer....on the later rear
drives.... it is easily stripped. USE fresh crush
washers. I am not giving a value for torque on that
one...do it GENTLY by FEEL. You don't have to use that
plug, you can fill 350 cc by measuring. I do check at the
hole. On disc brake rear drives you may find a
"min-max" in the casting outside...that was for the
drum brake version, for the shoe wear indicator that fit onto the
lever/shaft area.
The input nut of the rear drive (that means the large nut at the input gear where it fits the driveshaft housing) is to be BLUE Loctited and at 150 Nm, or 110-120 ftlbs. There is a threaded ring in that area,...so if you are fixing a stripped plug or changing the input seal you should know about that threaded ring, which is 110 Nm, or 81-85 ftlbs. AGAIN: pre-1976, use sealant under the washer and on the splines of the input nut, and all years of nuts should be BLUE Loctited....and TIGHT! I have seen them wrong from the factory. ...and loose!!! If you EVER have the rear drive off, check that nut! Under the nut and washer is a special plastic seal that is supposed to stop oil migration down the inside splines. I use sealant on the splines as noted earlier, on ALL years. Don't forget a new plastic ring seal that goes under the large washer that is behind the nut.
The question will arise as
to HOW one can loosen or tighten that nut, as the crown gear will
then try to rotate. No, you don't have to make a special
tool. TRICK!!......reinstall the rear drive and
the wheel/tire. This time, do not connect the driveshaft
housing....and have the drive nose face rearward. Got
it??
:-)
Another method of doing the above is to use a very strong bungee wrapped around the nose, and over the tire/through the spokes....in such a direction that the loosening or tightening will tighten the bungee....sneaky, eh?! Ed Korn makes a tool, if you insist.
For
the INternal seal:
I will assume that you have the unit
partially disassembled already:
Have the right side upwards and heat the housing carefully
until the bearing falls out, then remove the axle sleeve.
Put the bearing in your freezer. There is a slot behind the
seal, use some sort of tool, such as a screwdriver, and twist the
seal and cave it in, and remove it. Use BMW's tool, or make
ups something suitable, to install the new seal.
Reheat the housing until the bearing, removed from the freezer,
will fit in by hand with no pressing needed. With the
housing still hot, install the axle sleeve and leave the LEFT
side upwards whilst the assembly cools (that way the bearing
stays in place).
Leaky
driveshaft drain plug:
Usually this is due to the threads being stripped from
overtightening. If the threads are buggered, or not
repaired at exactly 90°, the plug does not go in
straight. You CAN NOT repair the drain plug threads
properly with the drive on the bike, NOR without disassemblying
some of the nose area of the drive, due to an internal threaded
ring, that you probably won't see any of from the assembled
drive...but you WILL damage things if you just try to re-tap the
hole, or, worse, drill and install a Helicoil. The proper fix is
to remove the rear drive and install a Helicoil. You need
two special tools, and heat, and a new seal.
Some folks will, temporarily, just seal the plug with some sort of sealant, as the driveshaft oil change period is not at all critical.
Other torque values you might like to know about during this job are the Shock Absorber at 37 Nm (27 ftlbs); the rear drive drain plug at 22 Nm (16 ftlbs); rear drive fill plug at 28 Nm (21 ftlbs); swing arm drain plug 15 Nm (11 ftlbs); swing arm fill plug 14 Nm (10 ftlbs).
NOTE!....I almost never actually use a torque wrench on the drain and fill and inspection holes. This is particularly so on the driveshaft drain; and MOST particularly so on the later drives that have the oil level inspection plug at the rear of the drive....it is very easy to strip the threads, even if using a torque wrench. There is NO need for those to be overly tight. Please use the above noted torque values with some common sense. NOTE that the inspection plug torque is not listed, on purpose!
Remember that in greasing the splines before installing the wheel, that the wheel cup splines, not the crown gear splines, get the real greasing, to avoid moving dirt into the new large seal as the wheel is put back.
Mind the caution on the driveshaft housing bolts.
Monolever and
Paralever models:
These models do NOT have an axle, do
not have two shocks units, and do NOT have rear drive splines nor
a rear wheel cup spline. What wears on these is the
left oil seal, similar to the twin shock type of
design. On these models, the wheel bearing, as such,
is the large roller bearing INSIDE the rear drive...and it will
wear and exhibit excessive clearance and wheel play,
etc. Replacing that bearing is not for the amateur
(generally), but the seal replacement is somewhat similar to the
twin-shock units. These models have a large
ring gear bearing, it is 85 x 120 x 18 mm, and is a grooved ball
type, with a official size of 61917C3. There is a smaller
internal bearing, 25 x 52 x 16.25, a tapered roller type, the SKF
number is 30205
Revisions:
02/06/2003: add additional information on rear drive brake
shaft O-rings and tube alignment
02/22/2003: Move red HINT to,
and make new, section II.
04/22/2003: minor changes; include references to removing
the left plate for sending off; clarifications mostly.
05/26/2003: hyperlinks, Honda moly paste
08/10/2003: Expand III greatly
01/17/2004: minor updates and clarifications.
07/28/2004: edit entire article, and also add more detailed
information about Hansen's
07/10/2005: slight updates, especially some
clarifications...but nothing major or very important
07/17/2005: revise for clarity
07/26/2005: minor editing about the cam rod O-rings and
shaft changes; add to mono and paralever bearing numbers.
03/14/2006: Add extensive notes on doing the Spline Cup
replacement
07/24/2006: two cautions added and emphasized
08/14/2006: edited and updated for seals especially
12/29/2007: /5 rear wheel cup note