The Stovebolt Site Forums The Shop Area Driveline SM420 propshaft brake question

I picked up a junk SM420 that had an intact propshaft brake assembly that matches the one in my '57 3600. I pulled all of the propshaft brake parts to keep them as spares.

I think that there are two versions of these brakes...one for the 3/4 and 1 tons and another for the bigger trucks. Mine has one piece drum that bolts to the tranny output shaft that holds the flange for the u-joint. The drum fits inside a brake band assembly. When engaged, the band snugs up around the drum and locks the propshaft.

I always assumed that friction material on the band was just regular brake shoe lining. I never looked close when I adjust it, just made the assumption. The material in the one that I took apart looks to be some kind of thick fiber webbing that is riveted to the outer metal ring. Maybe asbestos webbing? Here is a picture--

http://s844.photobucket.com/user/ma...2232_zpsh7iqdoqb.jpg.html?sort=3&o=0

Anyone know what this stuff is just in case I ever need to put a new liner into the band?

Matt

That brake was used on just about everything including Willys CJ's and most 3 and 4 speed transmissions from numerous manufacturers using the driveshaft brake. The original band was made from woven asbestos.
It would probably be best to take it to a brake & clutch reline shop if you have one in your area. I'm not sure anyone is using asbestos lining anymore but I'm sure they would have a suitable lining material.
Fred