rear drum to disc conversion

[upside2k]

Hi there,

I just bought a replacement differential for my 67' 230SL. It is a 71' 280SL unit with disc brakes. I did get the calipers with it. I realize I can simply buy discs and parking brake shoes for the replacement, but I did not get the small internal parts for the  parking shoes( star expanders, springs, etc.).

I can't tell if I can simply slide out the axles and change the backing plates to the drum plates, which seems easiest.Does anyone know where to find these small disc brake parts or have any experience in converting the 71' axle to my 67' drums? Do the axles slide out without taking the differential apart?  

Thanks for any help, John

[waqas]

Much has been posted about axle conversion. It will be much simpler to replace the entire rear-axle (including differential). Folks have done it for other reasons than disc brakes: gear ratio reduction. Here are some good threads to start with:

http://sl113.org/forums/index.php?topic=5958,axle,conversion
http://index.php?topic=6804
http://www.sl113.org/forums/topic.asp?ARCHIVE=true&TOPIC_ID=1195

[upside2k]

Thanks,  Let me say it another way.I have the entire rearend ready to bolt in, including the calipers. I am missing the parts( springs, stars, levers, etc.) necessary to assemble the parking brake. I know I can buy the discs and shoes but have no idea about the working parking brake parts. So, I thought that if the axles simply slide out , I could mount the drums on the 71' banjo if the disc parts are unavailable. It may be obvious to you if the axles  slide out, but I can't tell from the info I have--- do they?. If I must disassemble the diff. to remove the axles, I will probably rather hunt down the disc brake parking  parts . I do not want to disassemble the banjo... looks complicated.

[waqas]

Hello John,

I believe the structure around the ends of the axle-tubes are very different for the drum brake version, as compared to the disk-brake version.  I don't think you can simply bolt-on the drums (or vice-versa), without some significant welding.

Regarding parts, they are far more common for the later disc version. In fact, you might be able to find the [parking brake] interior drum parts from a parts recycler. A possible source would be http://www.porfor.com (others are aplenty).  Also, you might want to call up the classic center and get a baseline for new replacement parts beforehand.

I might have some parking-drum parts somewhere in my garage, so let me know if you turn up empty-handed elsewhere.

Finally, try to keep your old axle and drums around (if you can). The original 3.75 ratio axles are getting harder and harder to find. Also, the drums alone are worth a small fortune (new drums run upwards of 1k each).

[Naj ✝︎]

quote:Do the axles slide out without taking the differential apart?

Thanks for any help, John

Yes, they do. Sometimes with a bit of persuasion.

You will find the axle tubes are different. On the drum brake axle, the slave cylinders mount on the brake back plate which bolts to the axle tube with six bolts (together with the axle bearing carrier).
On the disc brake axle, the calipers mount on the axle tubes itself and the mounting points may be in the way of the drum brake back plate.

Need to check if the axle shafts are interchangeable or not  :?:

naj

[upside2k]

Thanks for all your help!!!

I should have called my local parts guy first. He has the full set of manuals with the blow up of the parking brake. So It was easy to see how I could make the parking brake work. Randy has the expander, adjuster, and all the other parts required. I'll stick with the discs.

I have bought parts from Randy Steele for 15 years and always find him helpful, and knowledgeable.

If you have a problem try him:

www.autopartsguru.com

Thanks again

[Benz Dr.]

You can't put drum on a disc brake axel. Why would you even want to?
If you change to a disc brake axel you need one part that's often left out. The brake pressure regulator needs to be installed under the floor near the end of the main brak line running to the back of the car. A small bracket would need to be welded on to mount the regulator.
Failure to use this part could result in loss of control under heavy braking in wet conditions. Everything you need is still available and regulators rarely fail so a used one would be a good option.