- Parts List
- Swing Arm Hardware and Boot
- Installing the Swing Arm
- Connect Drive Shaft to Transmission Output Shaft
- Final Product
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:
Here is the parts list of new parts I purchased.
|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|
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.
Swing Arm Hardware and Boot
Here is the swing arm hardware.
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.
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.
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.
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.
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.
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.
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.
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.
I have a cut down 27mm socket that fits inside the hole in the frame.
And then I torqued the lock nuts to 75 FOOT/pounds and put the plastic caps on. Here is the mounted swing arm assembly.
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.
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.
First, I put some Moly-60 paste on the rear wheel drive splines.
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.
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.
Then I mount the tire on the rear drive splines, insert the axle and snug the axle bolt.
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.
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.
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 New Fill and Drain Washers
I removed the fill and drain plugs on the rear drive and swing arm and installed new washers.
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.
2017-11-21 Note about best method of lubing rear drive to wheel hub splines.