Contents
I’ve already installed the engine and the transmission. You can see how I did that here:
Earlier, I replaced the swing arm bearings and refinished the rear drive and you can read how I did that here:
Parts List
Here is the parts list of new parts I purchased.
| Part # | Description | Qty |
| 33 17 1 230 304 | Drive shaft boot | 1 |
| 33 17 1 230 287 | Swing arm gasket | 1 |
| 33 17 1 230 297 | Swing arm rubber boot tension strap | 2 |
| 31 41 2 000 331 | Swing arm dust seal, 1970-1980 | 2 |
| 26 11 1 242 297 | Drive Shaft Bolts, M8x1x13 (New Style), no lock washers | 4 |
Preparation
I used some protective matting I got when the powder coated parts were returned to me to protect the frame and swing arm from getting scratched.
Rear of Transmission with Drive Shaft Coupling (Upper Right) and Frame Protection
Powder Coated Swing Arm with Drive Shaft Inside
Swing Arm Hardware and Boot
Here is the swing arm hardware.
Swing Arm Pivot Pins, Lock Nuts and Plastic Caps
The pivot pins screw into the swing arm and through the hole in the swing arm bearing seals. The lock nuts hold the pivot pins in place after the bearing pre-load has been set. The plastic caps help keep water and dirt out of the swing arm bearings.
This is the rubber boot that goes between the transmission output shaft and the swing arm and the two metal straps that secure it.
Swing Arm Boot-Rectangular Section & Straps
Note the rubber boot has a rectangular hole end (shown above) and a round hole end (show below). The end with the round hole goes on the transmission housing and the rectangular end goes on the drive shaft.
Swing Arm Boot – Round Section
The round hole end of the boot has markings to indicate this end of the boot goes next to the transmission (GETRI SEITE). This photos is not sharp but you can see where the lettering is on the boot.
Swing Arm Boot – “Getri Seite” on Round Section
On the opposite side of the round end is OBEN which means “Top” in German. Note that only the “EN” of OBEN is visible on this boot. Here is how the boot mounts on the transmission with the OBEN marking at the top. I put the strap on the transmission housing with the screw on the top so it can be easily loosened with a screw.
Swing Arm Boot – “OB” EN (Top) on Round Section
——————
Note: I took this picture when I finished mounting the swing as the first picture I took was too fuzzy. So, at this point in the process, I haven’t attached the round end of the boot to the transmission yet.
——————-
Installing the Swing Arm
Here is the rectangular end mounted on the swing arm. I put the strap on so the screw is on the bottom to make it easier to insert a screw driver when the boot is installed. If the screw is on the top it is hard to get to as the battery box is above it.
Swing Arm Boot and Rear Strap Installed
Mount Swing Arm in the Frame
I inserted the swing arm from the back of the frame in between the two horizontal frame so the bearings are aligned with the pivot bolt holes in the frame. I inserted the pivot bolts with the threads facing to the outside and finger tightened to hold the swing arm in place.
Swing Arm Pivot Bolt Inserted into Frame and Swing Arm Bearing
Center the Swing Arm
I used an Allen socket on each pivot bolt turning each about the same number of times until they were just snug and the swing arm wouldn’t move side-to-side. The swing should be centered so the drive shaft aligns with the transmission output shaft. I used a vernier caliper to adjust the gap between the frame and the swing arm boss so the difference in the gap on each side was within “0.020” inches.
Measuring Swing Arm Gap to Center the Swing Arm
Torque Swing Arm Pivot Pin Bolts
When the swing arm is centered, I torque the pivot bolts to 15 FOOT/pounds to set the new bearings into their races. I found that torquing each about a 1/2 turn and continuing to alternate between them helps keep the swing arm centered. Then I loosened the pivot bolts and set the torque to 7.5 FOOT/pounds or 90 INCH/pounds. I checked the spacing again between the swing arm and frame to ensure the gaps where within 0.020 inches.
Torque Pivot Pin Bolt Lock Nuts
Next I finger tightened to large lock nuts on the end of the pivot pin bolts.
Adding theSwing Arm Pivot Bolt Lock Nut
I have a cut down 27mm socket that fits inside the hole in the frame.
27 mm Cut Down Socket
27 mm Socket on Swing Arm Pivot Bolt Lock Nut, Torque to 75 FOOT/pounds
And then I torqued the lock nuts to 75 FOOT/pounds and put the plastic caps on. Here is the mounted swing arm assembly.
Swing Arm Mounted in Frame
Connect Drive Shaft to Transmission Output Shaft
I use the new 13 mm long drive shaft bolts without the lock washers (Part# 26 11 1 242 297). The older bolts are 14 mm long (Part# 26 11 1 230 414) have lock washers (Part# 07 11 9 930 840) and the washers have been known to crack, so the new bolts without lock washers is the preferred part.
I don’t have the special BMW tool for torquing these bolts. Instead, I use blue Locktite on the threads and tighten them firmly with a 12 sided 10mm wrench with a ground down back side. Getting the bolts threaded requires some patience. I pull back the boot and rotate the drive shaft coupling to line up the holes with the transmission output shaft holes and then finger tighten them. It’s fiddly work. I managed to drop one bolt into the drive shaft housing. I fished it out with a magnetic pickup. I keep the swing arm horizontal using a jack stand. That kept the bolt from going down the swing arm tube.
Finger Tightening Rear Drive Bolt
Mount Rear Drive on Swing Arm
I want to use the rear tire to prevent the swing arm from spinning when I tighten the drive shaft bolts, so I mount the rear drive on the swing arm.
Refinished Rear Drive
First, I put some Moly-60 paste on the rear wheel drive splines.
NOTE:
To avoid pushing dirt, grit and old rust into the rear drive seal, the better approach is to apply the lube to the wheel cup splines, NOT the rear drive splines. The lube is applied from the inside edge and pulled to the outside to prevent pushing crud toward the seal. I cleaned the cup and the rear drive splines well prior to installing the rear drive and wheel to get rid of any contamination.
Applying Honda Moly-60 Paste to Rear Wheel Drive Splines
Next I put on the new gasket and then put the rear drive on the end of the swing arm. I torque the nuts to 30 FOOT/pounds.
Rear Drive Gasket Installed
Rear Drive Installed
Then I mount the tire on the rear drive splines, insert the axle and snug the axle bolt.
Rear Wheel Installed
Torque Drive Shaft Bolts
I put the transmission in gear and sit on the rear tire as I tighten the drive shaft bolts with a 12 sided 10 mm wrench.
Sitting on Rear Tire to Tighen Drive Shaft Bolts
I find it easier to get the wrench on the bolt head if I rotate the drive shaft so the bolt is on the outside of the shaft as this seems to offer a bit more clearance between the bolt head and the U-joints.
Tightening Rear Drive Bolt w/ 12 Side 10 mm Wrench
Attach Drive Shaft Boot to Transmission
I removed the screw from the metal strap so I could put it around the transmission housing. I aligned it so the screw was on top to make it easy to remove the strap in the future.
Install Swing Arm Boot Front Strap on Transmission Housing
Install New Fill and Drain Washers
I removed the fill and drain plugs on the rear drive and swing arm and installed new washers.
Final Product
I removed the rear wheel and support the rear drive with a jack stand and the axle. It’s ready for installing new brake shoes.
Swing Arm Supported by Jack Stand
Swing Arm and Rear Drive Installed
Revisions
2017-11-21 Note about best method of lubing rear drive to wheel hub splines.
Pingback: 1973 BMW R75/5 Rebuild: Install Swing Arm and Rear Drive | Motorcycles & Other Musings
Hi Brook
I’ve been using this site, as I said before, a great reference!
Motors out, swing arm off, frame apart, etc., all good and ready to head to powder coating.
Question. Where the swing arm connects to the frame via pivot pins screws. The threads the pivot screws go through, on the frame, do those somehow come out or need to be removed? Can they stay in (if well protected) for the powder coating?
I didn’t or haven’t seen anyone referencing to remove that inner hardware?
Thanks Brook. Any advice would be much appreciated.
Pat
Hi Pat,
I’m glad this material has been helpful to you. It sounds like you are diving in and engaged in a pretty full rebuild.
The threads in the swing arm don’t come out as far as I know. I made sure my powder coater knew to put a rubber plug in those holes to protect the treads from powder coating with some tape marked “Do Not Powder Coat”. That said, I did have to clean some powder coat out of the holes for the swing arm bearings so I should have flagged those with some tape “Do Not Powder Coat”.
Best of success on your project.
Brook.
Hi. Thank you for the pictures. Helps us visual learners! We are having a heck of a time centering the swing arm after replacing the transmission. It is very hard to tighten the left side pivot bolt and the swing arm moves completely over to the right, not centered at all. Anything we can check or try? The bike is completely together, and the swing arm was never taken off. We just want to center it. Thanks!
Hi Erika,
I’m glad the pictures have been helpful.
As to your difficulty, I’m not exactly sure I understand things. I conclude you removed the transmission and now have installed it again. That often means you disconnected the drive shaft from the transmission and removed the swing arm so there is enough room to get the transmission off the engine output shaft. But, you said “… and the swing arm was never taken off”.
So, I conclude you removed the swing arm pivot bolts and removed the transmission with the drive shaft and swing arm attached as a single assembly.
Now, if I’m interpreting you comment correctly, you have the transmission attached to the engine again and you are trying to align the swing arm in the frame with the pivot bolts. But, it seems to have a bias toward the right side of the frame.
A thought is that the drive shaft coupling which attaches to the transmission output shaft with four stretch bolts (one time use) maybe hung up on the inside of the swing arm so it is cocking the swing arm to the right. This is just a guess. But, if true, then the swing arm is not free to move left or right and that could explain why you have a lot of resistance when you try to align it with the pivot bolts. You can remove the metal strap the holds the rubber gaitor over the drive shaft coupling and pull the gaitor toward the rear to see if the drive shaft coupling is caught or bound up.
Another possibility is that the threads in the frame the pivot bolts thread into have gotten buggered and so the left side pivot bolt isn’t working. That should be pretty easy to check I think.
I’ve not had a problem such as you describe. Usually I remove the drive shaft from the transmission and then remove the swing and drive shaft from the frame before I remove the transmission.
I hope these ideas of mine are helpful.
Best.
Brook.
Hello from Norway.
What a great site! Your write ups have been a great help.
I have a question regarding alignment of the swingarm. What do you align it to? So the clearance to the frame is the same on both sides? No site really makes this clear. Should it be aligned so the drive from the transmission lines up to the drive shaft. Should one bolt the entire drive train together and then mount the swingarm pivots? Any tips?
In advance thanks, and merry christmas 🙂
Hi Robert,
Thanks for stopping by and taking a look at the write-ups. I hope to post some more content soon on engine work.
Perhaps I don’t understand your question correctly, but as I show in this write-up, the method for aligning the swing arm and associated drive shaft inside is to measure the clearance between the frame and the outside edge of the swingarm (see picture “Measuring Swing Arm Gap to Center the Swing Arm”). Setting an equal gap on the left and right ends of the swing arm is all that’s required for correct alignment.
The transmission aligns with the engine when mounted to the back of the engine, so you don’t have to worry about that when mounting the swing arm to the transmission with the four bolts found under the rubber bellows that mounts between the transmission output shaft housing and the oval end of the swing arm. The rear drive bolts to the end of the swing arm, so the rear drive is correctly aligned to the drive shaft so you don’t need to worry about that.
I hope this helps, and have a Happy New Year.
Best.
Brook.
Hello, This site is amazing and is exactly what ive been looking for. I was wondering what happens if you do not align the rear swing arm. Can that bend your drive shaft? The reason I ask is that I took my 1972 R75/5 to a local shop here and have been very unhappy with the work that they have done, I think when the took the bike apart they did not put it back together correctly. I noticed a slight wiggle/odd sensation when i would lean into a turn. I was looking over the bide doing random maintenance and I noticed a significant space between the right frame and swing bar with no space at all on the left corresponding side. Im going to take it back and have them fix it but I wanted to know if there was any lasting damage that could have cause.
Hi Christopher,
Well I’m sorry to hear about the unsatisfactory service on your R75/5. The failure of a dealer to do good work made me get more involved in learning all I can about these bikes (my carburetor fell off and parts were missing 😉 ). The result is this site.
I think the stress from bad alignment would be more on the drive shaft bearings than the shaft itself. Having it aligned is important, so by all means have them get it right, and if the shop doesn’t understand how to get it right, give them the link to this article.
Assuming you haven’t ridden the bike several thousand miles like this, there should be no damage to the shaft.
As to the “slight wiggle”, they may not have tightened the locking nuts on the swing arm bolts. Or the swing arm bearings may be dry or damaged. You don’t mention if servicing the bearings was included in the work you had them do. There is a torque sequence to set the bearings in the races correctly, so they should follow that procedure.
An alternative to consider is to find a mechanic who specializes in airheads and avoid all this in the future. Here is a link to a list of them.
https://micapeak.com/bmw/Airhead-Shops.html
And, you can always take the route I took, join the Micapeak airhead forum and start learning more and doing more of the maintenance yourself. You can join the Micapeak airhead forum at no cost by signing up here:
http://micapeak.com/mailman/listinfo/AIRHEADS
I hope this helps.
Best.
Brook Reams
If you measure say at the point where the stop light switch bolts to the frame, then the gap between the frame bracket and the ARM of the swing arm is greater on the RHS. However the measurement is not made there. The measurement must be made where the swing arm pins transit through the frame to the swing arm bearings. The gap between the frame and swing arms should be equal there. See Brook’s photo 10 down for the correct location of the measurement. Good luck.
Hi! Your work is just fantastic!!! Can i make you a question? I’ve recentely took out the old bearing from the swing arm.
Now is the time to put them back, but.. how deeper do i have to place them? Thanks for tour help!
Hi Giuseppe,
Thank you for the kind words. The outer bearing race is driven until it won’t go any farther. There is a shoulder in each hole so the race ends up positioned at the correct depth.
I hope that helps.
Best.
Brook Reams.
Hi Brook,
I have a question you may be able to help me with, the site is awesome and very handy for bits im not sure on, I have just however got my swing arm back from being powder coated and am ready to re install, following what you have said here im am confident I can do it ok, however my bike is an 1981 R100 rs, mt question is, do you know if you need a thrust sleeve also on my model, as in the manuals it says you need a thust washer/sleeve also. as it wasn’t me that stripped it down I don’t quite know if im about to out it together correctly!
Regards
Ross
Hi Ross,
I haven’t worked on the swing arm of my 1983 R100RS yet. You have a 1981 RS so I used the RealOEM parts fiches to see if that part is used on the 1981 RS model. I used June for the month of production:
–> http://www.realoem.com/bmw/enUS/showparts?id=0437-USA-06-1981-2474-BMW-R_100_RS&diagId=33_0634
That part is greyed out indicating it is not used.
I hope this helps.
Best.
Brook Reams.
Hi Brook, I’m a new wrench to my R60/5 but I think those grayed out numbers only mean they don’t stock them? Just a guess on my part.
Regards
Old Wayne
Hi Wayne,
I’m not sure what “grayed out” numbers you are referring to. If you are talking about a parts fiche, the MAX BMW one shows “NA” when BMW no longer makes the part available. The REAL OEM fiche has “ENDED” when the part is no longer available, IIRC.
Best.
Brook.
Good morning, Brook,
Like many before me, I just want to take a moment to thank you for your great documentation, and pictures. Today I will be replacing my swingarm, per your write-up, Snowbum’s writing, and even a You Tube video I found. Yours is the most complete and orderly, and your detailed pictures really make the difference to make it the best reference of the three. And I learned that OBEN means “top,” and that clears up that little matter. Thanks so much.
Hi Peter,
Cool beans. I’m pleased this content provides a clear approach to doing this work. Best of success.
Best.
Brook.
Where can I buy a 27 mm Cut Down Socket?
Hi Adam,
Here you go:
http://www.cycleworks.net/index.php?main_page=product_info&cPath=28_2_16&products_id=58
Best.
Brook Reams.
Hi Brook,
quick question concerning adding fluid after re-positioning the swing arm cover boot and tightening the metal straps..On one picture I noticed a white plastic tip inserted in the odometer cable housing, is this where you add oil to top off transmission fluid?
my bike is a 1972 R75/5..
Hi Thierry,
No, that is where the speedometer cable goes retained by a special bolt with a hole down the center to let air pressure equalize. The transmission fill is on the left side of the transmission near the shift lever. I used the plastic tip from an old silicone seal tube to keep things from falling into the speedometer cable hole.
The drive shaft is filled from the bolt on the front of the rear drive housing where the other end of the drive shaft engages the rear drive.
Hope this helps.
Best.
Brook Reams.
Your write up has been my bible for the restoration that I’m undertaking on my ’71 R75/5. I can’t thank you enough for the thorough job you did with the pictures and written detail. It’s been two (2) years and I hope to be road-worthy by next Spring.
I’m currently installing the swing arm / rear drive and I wonder about connecting the drive shaft to the transmission output prior to setting the gaps and aligning the swing arm. My thought is that if the connection of the drive shaft and the transmission output shaft are aligned and tightened with the new stretch bolts that there is little chance that there could be any misalignment. Am I all wet with this thinking? I’d like to know your thoughts.
Thanks again for being my guiding light on this project.
Regards
Hi Dennis,
It’s good to hear my write-ups have been helpful to you. It sounds like you are in the home stretch on your project. 🙂
You need to align the swing arm ensuring equal gaps where the arm attaches to the frame. This does not happen automatically. Not having it aligned is not good for the universal joint that attaches the drive shaft to the transmission output shaft. I show how to do that and it’s not hard, but can be a bit fiddly to get the gaps even within “0.20 inches”.
I hope this helps.
Best.
Brook.
Hi Brook,
Thanks for the detailed write-up! In one of the previous posts you talk about powdercoating the swing-arm with the driveshaft in place. Have you found any problems with the bearings in the U-joint due to the heat of the powdercoating process or anything else? The driveshaft in my ’78 R80/7 is in there tight (as it should be) and several workshops are scared of pushing it out with their press and I am now considering powdercoating it with the shaft in place (taped off and such). Because of the price of a replacement (~€400,-) I want to consider all options before messing it up 🙂
Also, to what torque have you tightened the 24mm nut on the driveshaft itself? I was able to undo this one, but have it now tightened to 180nm.
Regards,
Eyle
Hi Eyle,
The safest way is to remove the drive shaft before sending the swing arm to the powder coater.
I would NOT put the drive shaft out of the swing arm. You will damage both.
Here is a link to a list of most all torque values for an airhead.
–> http://bmwmotorcycletech.info/torquevalues.htm
I hope this helps.
Best.
Brook.
Brook I’ve noticed you applied Honda Moly 60 to the spline side of the wheel. I thought that I read that Snowbum recommends applying moly to the wheel cup side only, not the wheel drive spline side? Is this right or am I reading it wrong? http://bmwmotorcycletech.info/rearwhlsplines.htm
Thanks for the help and the great site.
Cheers,
MikeQ
Hi MikeQ,
You are correct. Thanks for that tip. I updated the write-up with a note about this method.
Best.
Brook.
Love your site and detailed descriptions! I just went through all of the same procedures, however with one modification: I inserted and hand-tightened the drive shaft bolts BEFORE putting the swing arm back in the frame (I just let it dangle by the shocks and supported it from underneath). This made it very easy to screw the drive shaft bolts in. After hand tightening the drive shaft bolts, I put the swing arm in place and continued to follow your procedures. Just throwing out an idea to make life easier! Again, thanks for taking the time to write this up!
Brook, I am in the process of installing my swing arm and realized that there may be in error in the measurement of the gap in your description. You list it as 0.02 inches (0.5 mm), but I strongly assume it’s 0.2 inches (5 mm).
Hi Olaf,
I did not state the size of the gap. I stated the amount of difference in the gap that I want as I adjust the swing arm pivot pins. For example if one side has a gap of 0.15 inches, the other side should be no less than 0.13 or more than 0.17 inches.
I hope that helps.
Best.
Brook.
Hey Brook……very nice article my friend.
One thing I noticed. You installed the final drive on the swingarm and tightened the four nuts to 30 ft. lbs.. This locks the final drive in position but the final drive studs have room in the drive shaft holes to rotated a few degrees……so if the final drive was located & locked in a counter-clock-wise position (for instance) but needed to be in the full clock-wise position for the rear wheel axle to slide straight through…wouldn’t the rear wheel be leaned over to one side?
I think the final drive to swingarm nuts should be only put to 5–10 lbs and then the rear wheel installed completely so the axle would line up the final drive to the swingarm (rotation wise).
Snug-up the rear wheel axle nut to 10–15 lbs to center the final drive on the swingarm….tighten the (4) final drive (to swingarm) hex nuts to 30 ft. lbs….then take the rear wheel axle out and put it back in to see if it easily goes all the way through indicating the rear wheel & final drive (to swingarm) both are located where they should be.
Whatcha think buddy?
My best…….Mike
Hi Mike,
Interesting observation about the affect on rear drive alignment when tightening the rear drive nuts to the swing arm. I don’t recall any issue inserting the axle. That said, your approach eliminates any potential problem when inserting the axle due to a slight tilt in the rear drive.
Thanks for sharing.
Best.
Brook.
Hi Brook
Thank you for a such a detailed account on overhauling a R75/5, I have been restoring an R60/5, which was last run in 1990 and your log of each job has been invaluable.
I have found that when installing the swinging arm (SA) I could fit the 4 flange bolts attaching the drive shaft to the G/B output flange easily if the SA was not held by it’s pivot shafts. I rested the SA on a chair and slid the drive shaft forward as far as it would go, I was then able to install the bolts and torque them using a suitable extension on the torque wrench, selecting first gear stopped the shaft turning. The SA could then be slid over the shaft and the pivots and lock nuts installed.
I hope this may help future readers repairing their Airheads.
Kind regards
Martin Slater
Bourne, Lincolnshire, England
Hi Martin,
Thanks for the idea.
Best.
Brook.