33 BMW 1973 R75/5 Refinish Rear Drive

I’m not going to disassemble the rear drive as there were no problems with it. Since the rear brakes are mounted on the rear drive, I advise a face mask and gloves to avoid getting brake dust where it doesn’t belong, your lungs.

Here are the pictures of the rear drive when I took it off the bike.

Rear Drive Before Cleaning

Rear Drive Before Cleaning

Brake Shoe Orientation and Components

Brake Shoe Orientation and Components

I pulled the rear brake arm off the shaft so I can push the shaft out to remove the rear brakes. There is a felt ring under the arm.

Felt Washer Under Brake Lever

Felt Washer Under Brake Lever

Using a soft mallet, I knocked the brake lever shaft out the back to release the brake shoe assembly.

Removing Braker Lever Pivot Shaft

Removing Braker Lever Pivot Shaft

Then, using a screw driver I lifted the other side of the brake shoes over the fixed pivot to remove them.  Here is the disassembled brake components.

Brake Assembly Parts

Brake Assembly Parts

Inspecting the brake lining, I could see the lining had cracked, so some more parts to order.

Rear Shoe and Cracked Linning

Rear Shoe and Cracked Linning

And here is the washer that goes between the boss and shoulder of the brake shaft. It stuck to the boss.

Washer Between Boss and Brake Shaft

Washer Between Boss and Brake Shaft

I put the rear drive in a plastic pan and liberally applied Gunk engine degreaser and worked on the hardened grunge with a stiff nylon brush and tooth brush.  After rinsing the Gunk off, I used the parts washer and a tooth brush to get another layer of grime off the cast aluminum.  Then, using AutoSol aluminum cleaner and a Scotch Brite pad, I got the stains and corrosion off the housing. Then I used “00” steel wool with more aluminum cleaner get a luster on the rough casting finishing up with aluminum polish. On the left is the cleaned and polished casting and on the right is after parts washing with gear lube stains still showing.

Left-Aluminum Cleaner; Right-Parts Washed

On the inside of the drive where there was a crusty mix of brake dust, some brake cleaner did the trick. Using a stiff nylon bush and toothbrush, I got all the grunge off the nuts and casting.

I used Permatex gasket remover and a putty knife to clean the old gasket off the end that connects to the swing arm. I finished up with “000” steel wool to polish the surface making it ready for a new gasket.

Cleaned Gasket Surface

I used aluminum cleaner on the brake lever with “000” steel wool to bring the shine back finishing up with aluminum polish. The wire wheel cleaned the pivot lever, springs, brake lever Allan head bolt and the brake rod bushing. These I finished up with metal polish.

Refinished Inside Side of Rear Drive and Polished Parts

Refinished Inside Side of Rear Drive and Polished Parts

Refinished Outside of Rear Drive

Refinished Outside of Rear Drive

When the brake shoes come in, I’ll assemble the brake shoes and the rear drive will be ready for attaching to the swing arm.

6 thoughts on “33 BMW 1973 R75/5 Refinish Rear Drive

  1. Good morning from Canada!

    I have a question and was hoping to see if I can get some sagely advice. I am 25 and in the midst of my first rebuild – a 1970 Bmw 75/5. It’s been extremely fun and challenging and requires a lot of research. Now on to my issue:

    I am reassembling the rear end and when trying to put the rear wheel back into the final drive i am left with a 2-3mm gap all the way around. It should sit more flush to the final drive but no amount of maneuvering can get it to sit flush. Additionally, the gear ring on the wheel has some play (very minimal), do I need to re-rivet this piece and have it stay perfectly solid? An old bike mechanic in my area said it isn’t a huge concern, but now that I am here and having this other issue I wonder if I should just fix that as well. Any thoughts and insights would be greatly appreciated.

    • Hi Ivan,

      It sounds like you are having fun 🙂

      I think you would be well served to post a note to the Airheads forum with your question on the rear drive.
      http://micapeak.com/mailman/listinfo/airheads

      There are several very knowledgeable mechanics and owners on this forum and I’m sure they can advise you of what to do.

      I hope this helps.

      Best.
      Brook

  2. Hello Brook,

    Oil overflow through the breather located on top of my final drive (R75/6) appears to indicate a driveshaft-to-final drive oil leak caused–probably–by a faulty oil seal (the one located between the crown spline and the pinion).
    Do you have advice on where to obtain illustrated instructions on how to replace the old seal? I believe I will need a special tool by Cycle Works which allows for the removal of a four-slot “ring nut” which holds the seal, but other than that, I’ll have to adventure into unchartered waters.

    I believe common sense might help (plain reverse-engineering…), but I want to play it safe. Thank you as always!

    Best,

    Luis Etchenique
    South Ponte Vedra Beach, Fla.

  3. Thank you Brook; will follow your advice. In fact, I think I’ll be taking photos as I go–and I’ll forward them to you.
    Best,
    –Luis

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