33 BMW 1973 R75/5 Install Swing Arm and Rear Drive

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 & Drive Shaft  Coupling (Upper Right)

Rear of Transmission with Drive Shaft Coupling (Upper Right) and Frame Protection

Powder Coated Swing Arm with Drive Shaft Inside

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

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.

Rear Drive Boot-Rectanglar Section & Straps

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

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

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

Swing Arm Boot – “OB” EN (Top) on Round Section

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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

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

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

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

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 Cut Down Socket

27 mm Socket on Swing Arm Pivot Bolt Lock Nut

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

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

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

Refinished Rear Drive

First, I put some Moly-60 paste on the rear wheel drive splines.

Applying Honda Moly-60 Paste to Rear Drive Splines

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 Gasket Installed

Rear Drive 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

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

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

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 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 Supported by Jack Stand

Swing Arm and Rear Drive Installed

Swing Arm and Rear Drive Installed

20 thoughts on “33 BMW 1973 R75/5 Install Swing Arm and Rear Drive

  1. Pingback: 1973 BMW R75/5 Rebuild: Install Swing Arm and Rear Drive | Motorcycles & Other Musings

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

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