disc brake conversion idea -- need feedback

[akahige]

New member looking for some expertise. I know this has been discussed to death, but...

I've got a Dana 70 full-floating rear axle that I'm interested in converting to disc brakes. The common thing is to use front calipers on custom brackets. The hitch -- if you want to call it that -- is that I want a "real" parking brake and not something like a line lock, so that pretty much eliminates the front caliper idea. That simple demand seems to have severely limited my available options (short of just coughing up boatloads of cash for an aftermarket solution).

In looking through every truck and offroad forum I could find and there don't seem to be a huge number of options. At least that people have worked out on their own. I may have hit on a "new" solution and was hoping to impose on y'all's expertise...

A lot of MFG's over the years have used D70's in all kinds of vehicles -- especially Ford, and they put disc brakes on 'em. And that got me to thinking. D70's or not, GM has taken to putting rear discs on heavy duty axles for more than a few years now, and those axles have real parking brakes. But what I've never seen anyone talk about doing is adapting a set of full-size rear discs in place of a set of full-size drums. And I started to wonder why...

To sum up, the standard alternatives for this sort of project seem to be:
1) Skipping the parking brake altogether
2) Using late-'70's Cadillac El Dorado calipers (which have an integral, though totally unreliable parking brake mechanism)
3) Using Explorer calipers since they have an integral parking brake mechanism. (Requires that you get blank rotors and drill them for the required bolt pattern.)

One's out of the question, two seems less than ideal, and I worry that the Explorer setup in general isn't heavy duty enough to stop a loaded 3/4 ton (despite the fact that it has the p-brake feature). Which brought me to the possibility of using a full-size Chevy/GMC brake setup. I don't know enough about the big trucks -- or the newer light duty ones -- to know how many years and which parts will interchange. My assumptions are that this is the drum-style brake that mounts behind the disc assembly, and that it will mate up with a standard cable actuator.

After reaching this epiphany, I'm also assuming that there must be some really obvious reason -- obvious to everyone but me -- why no one's done (or at least discussed) this. Every time the subject seems to come up, people are recommending the really expensive aftermarket disc conversion kits (Blackbird, Currie, etc.) over what would otherwise be an infinitely cheaper stock solution. The only thing that I can conclude is that people aren't generally looking to do discs on 8-lug trucks.

Anybody got any thoughts on that?

michael


P.S. If it matters to the discussion, it's a D70 dually axle going into a '63 GMC 3/4 ton p/u.

[krue]

No help on your question (waiting on the answer myself since I had a 70 3/4 ton fall into my lap) but I would like to welcome you to the board from South Mississippi!

[poorboy]

Welcome to the board. It might be easier to convert to a 14 bolt. Here's a link to a conversion that the guy says you can use Caddy calipers with the built in parking brake.
http://www.shakerbuilt.com/14_Bolt.html

[454_72_4X4]

I've wondered the same thing myself, but I decided I'll use the front calipers and a hydraulic locking brake. Much better than the cable activated mechanical parking brake IMO.
That's just me though.

Back to your question.
1. Like you stated, out of the question.
2. I agree with you about the Caddy calipers. There's also Camaro/Firebird calipers but I think they have the same parking brake assembly as the caddy calipers.
3. I'm not familiar with Exploder calipers, but as far as the rotors go, I would think you could use about any rotor as long as the thickness is close to the Exploder rotors.
You refered to a3/4 ton so I'm assuming you're thinking about this conversion for a 3/4 ton?
If so I doubt the Exploder calipers have the capacity for 3/4 ton rotors to fit inside, (unless you want to use 1/2 wore out pads...LOL)

Ford uses a Sterling rearend in their trucks as far as I know. I'm definately not a Ford expert though.
They also have a metric bolt pattern so the rotors would probably need redrilled also. (If thats possible)

One other thing, GM now offers rear disc brakes on 3/4 ton pickups. They still use the old bolt pattern but that's about all I know about them.

[454_72_4X4]

Oh, Welcome to the board from Misery!

[BUDDY]

Originally Posted by 454_72_4X4

One other thing, GM now offers rear disc brakes on 3/4 ton pickups. They still use the old bolt pattern but that's about all I know about them.

Read much?

Originally Posted by akahige

I worry that the Explorer setup in general isn't heavy duty enough to stop a loaded 3/4 ton (despite the fact that it has the p-brake feature). Which brought me to the possibility of using a full-size Chevy/GMC brake setup. I don't know enough about the big trucks -- or the newer light duty ones -- to know how many years and which parts will interchange.

You musta been in a hurry 'cause that's what he was asking about.

Anyways, my guess as to why this hasn't been figured out or tried yet is cost. Those newer, disk-braked rear axles aren't cheap, & neither are the parts for them. In some cases the 14-bolt is used with disk brakes on the ends of them, but most of the newer GM's & dodges I've seen, (esp dodge), have the MONSTER 11.5 AAM rear axle, & it's so new & big that there are hardly any parts for it at all.

However, it's entirely possible that you could get everything from the backing plates out, (rotors, calipers, e-brake assy, etc.), & figure out how to get it to work on you're axle & therefore a lot of other applications as well.

You may find that you wind up putting just as much money & more time into it as you would by just buying an aftermarket kit. Although I don't know of many for a D70.

I've often thought the same things about a rear disk conversion, & had the same resevations. I have many other bridges to cross & burn before I get there though, so I haven't done much other than the thinking.

Later,
Buddy

[454_72_4X4]

Originally Posted by BUDDY

Read much?

Huh?

[Budman56]

it would appear that this thread is dead but, I have started looking into this and have come up with the same conclusion about trying to find another vehicle with rear disc brakes to adapt my dana 70. in the end I have purchased the rufstuff brakets and now Im looking for the 76 caddy eldarado rear calipers and 75 3/4 front chevy disc. The only problem so far is finding a used set of levers and springs for the caddy calipers. other than that things are working out so far.

[maskale]

went down this road also, a rebuilt set of calipers from auto zone or other parts stores will cost around 300.00 without the springs and levers.

used ones on ebay go for around 100+ straight out of a junk yard, ie, need to be rebuilt.

NEW ones from an online website, google it, I cant remember the site, has them for around 325 shipped with the levers and springs.

I dont have my truck on the road yet, but the brakes are hooked up and they do work. What I have read is that they are self adjusting, and because people dont use them often they are considered unreliable. I only need mine for passing inspection, so once a year I'll adjust mine and pass my inspection. Adjusting is as simple as operating the lever severl times so it operates correctly. That is as easy as using the parking brakes several times, or sticking ur foot behind the wheel and mashing down on the lever several times with ur foot.

any questions PM me, I will probably forget about this thread.

[HEI451]

Just a couple of suggestions on parking brakes.

My 1964 C30 1 ton has a drum parking brake mounted directly to the flange out of the transmission, holds the drive shaft when engaged. It uses a band around a drum, and id mechanical. I have seen this type of brake on a few different vehicles, works well.

When I built my last '23 Model T short bed pickup, I used a disk brake on the U joint flange on the rear end, and a bracket I made to hold a Honda CB125 cable operated mechanical disk caliper, and that disk. When activated, this brake held a significantly larger/heavier vehicle we did this to as well, a Uni-Mog.

Many motorcycles, especially ATV's use things like cable operated drum brake and mechanical disks, and all that stuff is just a modification or two away.

Just some ideas for you to consider.

[Budman56]

Originally Posted by HEI451

Just a couple of suggestions on parking brakes.

My 1964 C30 1 ton has a drum parking brake mounted directly to the flange out of the transmission, holds the drive shaft when engaged. It uses a band around a drum, and id mechanical. I have seen this type of brake on a few different vehicles, works well.

When I built my last '23 Model T short bed pickup, I used a disk brake on the U joint flange on the rear end, and a bracket I made to hold a Honda CB125 cable operated mechanical disk caliper, and that disk. When activated, this brake held a significantly larger/heavier vehicle we did this to as well, a Uni-Mog.

Many motorcycles, especially ATV's use things like cable operated drum brake and mechanical disks, and all that stuff is just a modification or two away.

Just some ideas for you to consider.

I had seen some thing like you mention but I don't have a machine shop at my disposal. may be if we can get some photos of what your talking about it might help the group. I heave also heard that a drive shaft e_brake doesn't hold as well.
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