Six-lug rear disc brakes...

[More Power]

With the exception of some bolts, e-brake cables and a couple of flange adapters, I now have the pieces necessary to install a set of disc brakes on the back of lil Red.

http://www.thedieselpageforums.com/photopost/data/500/discbrakes01.jpg

The above shows the parts for one side.

Looks like less than $700 when complete.

MP

[CareyWeber]

Morepower could you tell the bolt spacing of the four bolts that hold the backing plate to the axle end for me. I'd like to know that for another project.

Carey

[More Power]

The bolt center to center measures 3.300" for both the axle flange and the disc brake backing plate.

The adapter needs to space the backing plate outward 2.270". The square end bolting to the axle flange is 5 degrees nose down, while the backing plate end is oriented with corners at 12 & 6 o'clock.

I have a rough drawing of the flange adapter that I'll include in an upcoming disc brake conversion article. Anyone have some drafting skills to turn this into an engineering drawing? $$

MP

[grape]

what master cylinder are you going to use?

[More Power]

I installed a new brake master cyl along with a new hydraulic brake booster when the truck was assembled. So, I plan to find out if the stock MC is up to the task. I suspect it will be, but I could install another if need be.... We'll see....

MP

[MTTwister]

MP - Is the original Drums? If so , are you using a Disk / Drum Prop valve? You probably won't want to use that in an all disk set-up (or all drum set-up for those really old cars). and is there no end to what you'll come up with?

Merry Christmas!

[More Power]

MT,

Yes, the truck had rear 10" drums originally. I'll add a disc proportioning valve if necessary, and add a newer 4-wheel-disc master cylinder if necessary (hope it doesn't get to that point).

Once the new brakes are operational, I'll give them a good test to determine what (if anything) needs attention.

MP

[DmaxMaverick]

Better get those brakes straightened out or you'll need a drag 'chute. Might need one anyway, eventually. If all goes well, NHRA will tell you to get one, before you actually need one.

[Herman_Bolger]

Has anybody done a rear disc conversion on an eight lug dually yet? will the 2000 model bolt in. we are looking at that and a rear air ride suspension, removing the leafs altogether.

[rjschoolcraft]

Drafting skills avaialable here! ;)

[More Power]

Ron,

Cool!! Thanks for offering to redraw my crude drawing. I'll clean it up a bit, then create a digital image that you can download.

The drawing will be included in the completed disc brake install piece, so others can follow this example if they choose.

I'm planning to contact a local drivetrain shop once I have the final drawing to see if they can produce the flange adapters. They've got all the cool automated welders that they use for welding drivelines and axle flanges, along with CNC water jet cutters and other tools that make things like this so much easier.

MP

[G. Gearloose]

awesome. Now does anyone know a reference procedure on how to remove the axleshafts on a stock G80 9.5"? Its not straightforward to me looking at one.

I have a factory manual, and its not helpful here.

[More Power]

Same as other GM diffs. Remove the carrier pin, push axle toward center, fish out C-clip.

MP

[G. Gearloose]

excelent, thanks!

[More Power]

Well, I drove the truck around the driveway (first time since late October....). New rear axle is in, along with the new GM disc brakes. I haven't taken it out onto the highway yet (maybe tomorrow).

Will have an update to add to the earlier disc brake piece perhaps by mid March that discusses the easy parts, the hard parts and offers a few recommendations. I should have plenty of brake testing completed by then. :D

MP

[mhagie]

MP, How did the 14 bolt end up with 6 lug axles?, I was always under the impression that the 14 bolt was 3/4 ton with 8 lugs.
I never knew that any 1/2 ton ever was equiped with a 14 bolt. :confused: ............Merle

[G. Gearloose]

Its not the monster 10.5" 14b full floater..
....its a 14 bolt semi floater, 9.5" gear, 6 lugs, in fact it was the standard 1/2 ton axle in '96 xtracabs, gas or diesel. It also was a common 8 lug axle on 2500's in the eighties.

[More Power]

The 14-bolt semi-float C-clip rear axle was available in both 8-lug and 6-lug applications (in the higher 1500-series GVW ratings).

http://www.thedieselpageforums.com/photopost/data/500/discbrakes2-01.jpg

http://www.thedieselpageforums.com/photopost/data/500/medium/discbrakes2-02.jpg

http://www.thedieselpageforums.com/photopost/data/500/discbrakes2-09.jpg

MP