There are three different sizes of drum brakes on the original 14 bolt, depending on the anticipated load mostly. I think any of the three would be just fine (even overly so) on the back of an FSJ if braking capability was the only consideration.
But we ain't building a hay wagon here, and ride quality is an issue that's important to me. Getting rid of the drums and going to disk brakes, reportedly, will drop about 50 pounds from the rear axle, even once all the disk brake stuff is installed. Hah, so now it only weighs 500 pounds! It'll ride like a Cadillac, not!
The other consideration with the drums, when from a later ('80s or '90s) trucks is that the drums are so dang big that narrowing the axle can put the drums into the leaf springs, and I want a more narrow axle than any of the stock 14 bolts can go with drum brakes, so discs it is. But I've got to have a fully serviceable parking/emergency brake that will work under all conditions.
The lever action Cadillac calipers are barely adequate (based on a lot of reading) for stock size tires on relatively level ground. The first comment made when discussing a TC brake is that it only works if your rear driveshaft is still intact (banish the thought!), and that by the time you've bought all the parts, plus the flanges, to make it work it gets very expensive, and, at least with the High Angle Driveline unit, it doesn't have much more holding power than the Cadillac calipers. I have read several threads from various boards that some of the serious guys will actually put a second hydraulic caliper at each rear wheel, plumb it with a completely separate system, and operate it with a lever operated MC. All things considered, that doesn't sound very expensive or difficult and would certainly work, and off-the-shelf brackets are available for the second caliper as well. But it has the same concerns as the line lock solution in that any sort of miniscule bypassing leak in the system will eventually allow it to "let go". Great for short intervals, a little less so for long duration use.
And the truth is that I don't know for sure how good the stock GM parking brake is in a later AAM axle, but I'm comfortable enough with the odds that I'm willing to give it a go. The stock parking brake in my Waggy will hold the truck on the steepest hill I'm likely to try, and that is with the trans in neutral, not park. If the later AAM parking brake can duplicate that feat, I think I'll be happy. Finding mechanical details on the later AAM axle is anything but easy, so I don't know what the diameter of that brake is, but I expect it's probably about eight inches in diameter. The brakes on the Waggy are eleven inches in diameter. I'm hoping for a lot of "mechanical advantage".
I won't have a functional axle to test for some time yet, but parts are supposed to start showing up in a few days.
On a side note, nobody I called even had any early dually hubs available, regardless of price! Axles go "complete", or not at all. I had to resort to ebay to get one
, but it's on its way too.
Chris
'84 GW, returning to service.
360, 727, Selec-Trac 229, TFI, Hydro-Boost, 4" all-spring BDS lift (what a PITA!), BFG/AT 31x10.5x15, 5125 Bilstiens
