The Stovebolt Site Forums The Parking Lot Tons 'o Fun Late model GM disc brake swap -- with parking brake

Brainstorming and info about late model disc brakes with "drum in hat" parking brakes.


These brakes come on 3/4 and 1 ton approximately 2000->present? GM 2500Hd and 3500HD trucks and I think also on some similar vans. I don't know all the exact models and what variations may exist, I think the list is quite broad, this is a very widely used disc brake setup.
The ones I have and the pictures to follow are from a 2007 model single wheel GM axle. More specifically an American Axle Manufacturing "AAM" 11.5" axle.
They would also come on the AAM 10.5" (new revised version of the old 14 bolt) and I think on some GM Dana axles that may be used in vans.

This is the axle as I found it in the junkyard. PICTURE 1
The whole axle is too wide for my truck, thus I want to only swap the brakes onto an axle that is the width I want. PICTURE 2

I'll use single wheels but just for fun/curiosity sake I test fit with a dual type 19.5" wheel, the dual wheel won't fit over this single wheel brake/axle setup. PICTURE 3 However brakes from a Dually axle (longer/taller rotor) should fit.

Couple pictures of the parking brake cables, they exit the rear and then turn forward. PICTURE 4 and PICTURE 5

The rotors are 13", and uses quite large double piston calipers in a carrier which then bolts to the caliper bracket bolted to the axle tube flange. PICTURE 6

The rotor just slides over the hub. Bore in the rotor is 4.834" (Excuse the grease from a bad hub seal) PICTURE 7

The hubs while very similar to the old 14 bolt will not interchange, the bearings are 1/2" closer together. From what I read if the (later model) axle has slide off rotors or drums it should have the short spindles, 4-3/4". PICTURE 8

The flange on the axle tube is slightly strange shaped, larger and different than the familiar square pattern found on Eaton and 14 bolt axles for years and years. PICTURE 9
The flange also has a pilot about 1/8" long to center the caliper bracket. The diameter is 3.807" this fits in a 3-13/16" bore in the bracket. PICTURE 10

The non symmetrical 4 bolt flanges are welded on the axle tubes in weird orientations because they do use the same caliper bracket on both sides, not mirror images. PICTURE 11
The following shots show those angles.
Start with the spring pads dead level. PICTURE 12
Drivers side flange has the widely spaced holes on top and it is tipped back 22° PICTURE 12
Passenger's side flange has narrow spaced holes on top and tilted forward only 8° PICTURE 13

Next I need to figure out how to adapt these brakes to a 14 bolt axle and maintain about 63" width over the wheel mounting surfaces.
To start with I'll have some flanges burned out and I'll machine the pilot on them. They can be very carefully welded on the axle of choice. (originally the flanges were welded on and then machined true)

For an expensive bolt on bracket solution for some 14 bolt axles look at picture and read the article titled "Affordable 14-Bolt Disc Brake Conversion" part way down the page here: http://www.fourwheeler.com/product-reviews/129-1107-july-2011-parts-rack-new-products/
At one time and perhaps still offered by Right Gear and Axle though not found on their website. Occasionally found listed by them on eBay for $269

*****
For some discussion and pictures of adapting this disc brake setup to the old Eaton axle check out this in the "Truck Parts for Sale"
Lots of good info in this document on installing the kit from Dave Chapman at The Hollister Road Company Install Doc
*****

I have not researched or confirmed these part numbers but they are what RightGear & Axle list in their ebay ad.
This info may be of use later.


Well I did check the Dorman studs listed 610-189.
9/16-18 - .622 In. Knurl, 3 In. Length
Application: Chevrolet & GMC 1999-71

And the rotors listed are for lots and lots of late model GM vehicles, might be same as came on the axle I have?

Carefully measured the backing plate flange on the AAM axle and here is the result.
Flange drawing PICTURE

If made with the 3-3/8" ID as drawn it would fit on a 14 bolt axle tube to be welded in place.
I can't find any logic or reasoning in the pattern beyond the 5" spacing on the wide holes. Doesn't fall into a bolt circle, or a nice angle between holes, and as you can see not clean x and y distances from center. Converted to metric the numbers aren't round/clean either. It is what it is...

Before right now I could not find this info anywhere at all on the internet.

Grigg

Well done Grigg!! Your like a 1 man research department. Keep us updated on your progress.

Grigg,
Your a walking encyclopedia! Really enjoy reading your post's

Briefly lets go over axle widths, hubs, rotors, and drums.

The Eaton H-072 as found under my 1951 1 ton GMC measures 62-7/8" from Wheel Mounting surface to Wheel Mounting Surface. We'll call this a "WMS measurement" in the future; it is from hub to hub at the flat surface where the wheels bolt on, measured without the wheels in place.
I'm reasonably sure the dual wheel AD truck axle is the same width as the single wheel version. Discussion on that Here

The GM 14 bolt axle found under a Cab and Chassis (C&C) truck is often said to be 63 or 63.5" wide. Here are some pictures of these C&C axles: PICTURE 1 and PICTURE 2
I measured (with confidence) one at 62.75" C&C WMS PICTURE

The 1973-1988 14 bolt C&C at ~63" WMS is a very nice match/replacement for the old Eaton axle in the AD 1 ton trucks also with ~63" WMS
GM made a revised version of the 14 bolt starting in 1989 and later further revised it and still made today by AAM. It can be confusing but there is a lot of info on the 14 bolt here as well as by searching the net. http://www.pirate4x4.com/tech/billavista/14b_bible/

The C&C 14 bolt has the narrowest WMS available. Other widths of 14 bolt axle do exist. Van axles are quite wide (70"?) and not very well documented, lets ignore those. Single wheel truck 14 bolts are about 67.5" wide WMS. Not common but a dual wheel axle from a pickup truck (with pickup bed) is around 72" WMS.


Hubs,
The 14 bolt has 2 major hub types. (Other types exist where the rotor or drum slips over the hub. We will not go over these.. because of a shorter spindle I don't believe they are interchangeable with the other types )
The two major types are the dual wheel hub which makes the wheels sit in pretty narrow, the hub sticks out past the WMS 3.850" Dual type hub PICTURE
The single wheel hub makes an axle with wider WMS. The hub sticks out past the WMS 1.830" Single type hub PICTURE

The eaton axle hub can be swapped with some different bearings onto the 14 bolt axle spindle. Discussion and details here
The Eaton hub (only one hub for both dual and single) sticks out past the WMS 3.350" PICTURE

A 14 bolt single wheel axle can be made narrower by installing the dual type hub to achieve the very same WMS as a C&C axle, about 63". However the brake backing plates will be very close to the hub, they'd need to be relocated to fit drum brakes on this combination.

My calculations show the eaton hubs on a C&C or single wheel 14 bolt wold result in an axle about 64" WMS. Idelaly someone would do this swap and get real measurements because not 100% accurate to compare hubs like I did by how much sticks out. (It would be better to compare location of WMS to the back side of bearing inner race).


Finally drums and rotors, lets just cover how they fit and are attached to the hubs saving all the nit picky details for the next post.

The drums on the older 14 bolts are piloted to the hub (snug fit between bore in drum and hub OD) and then held on the back side of the hubs by the pressed in studs. PICTURE

Late model disc brake rotors and the original Eaton AD truck drums simply slide over the hub and studs same as, and just before, a wheel is installed.
They are also snugly piloted to the hub like the drums above are. PICTURE late disc and PICTURE Old Eaton drum both removed

lets discuss rotors and how they fit the hubs.
The rotors I have on the 2007 axle are eqivelent to NAPA # 86828. Catalog page, rotors by size
They have a measured 4.836" bore (catalog list 4.830") PICTURE

Both Right Gear and Axle as well as The Hollister Road Company use a rotor equivalent to NAPA # 86830 which is very very similar to the rotors that came on my late model axle but these have a 4.641" bore (measured) PICTURE

PICTURE showing difference in these 2 rotor bores.

Lets compare these bores to that of the 14 bolt or Eaton brake drum we'd like to replace. PICTURE 14 bolt Drum and PICTURE Eaton drum
These drums measure 4.597" ID, and fit snug on their hubs.

Pictures of the different rotors on 14 bolt hubs:
PICTURE Larger ID, sloppy fit.
PICTURE Smaller ID, still 0.044" of slop (quite noticeable).


I don't think either rotor is ideal because I want the rotor to be well supported and centered by the ID fitting snug on the hub OD. Just the same as all the drums and rotors in question fit in their respective/original hubs.

One possible solution is use the larger ID rotor and make a bushing to shrink fit on the hub.
Another solution is use either rotor and machine the flange on the hub thinner at the same time turning a snug pilot to fit in the rotor.

Grigg

Grigg, when we spoke a week or so ago, I forgot about some of the pics on my photobucket page.

Here's a dually hub on a 67" axle. (Making it a 63") Since the late model rotors won't slide over the early hubs, I have it on the backside. http://s1074.photobucket.com/user/w...mp;_suid=1454023010427028238838450720316

You can see that there is some clearance issues with the early 14 bolt flange. With a 63" axle, it may not be a problem.

The late model GM vans and Single wheel trucks use the same rotor assembly. However, the caliper is different between the two.

Van Bracket- http://s1074.photobucket.com/user/w...amp;_suid=145402400967005775784978155909

Truck Bracket- http://s1074.photobucket.com/user/w...amp;_suid=145402408403406277164560249216

The Van Calipers are almost identical to what 1500 series trucks and Tahoes use, they may even interchange.

The 03-05 2500 series vans had 2 axle options. The 7500 lb axle used the same brackets with a slightly smaller piston in the calipers and a 6 lug rotor. I think this may be a better option for our trucks and may be something for the 1/2 ton guys to think about. The 8500 lbs axle used the 8 lug rotor and the larger caliper.

I've talked about it before, I'm using the Eaton hubs on my 14 bolt. The rotors will slide over them. However, I do plan on drilling the rotor and using the tapered bolt, like what the early drums had. This will keep them nice and centered.
http://s1074.photobucket.com/user/w...amp;_suid=145402451224702610842115455898
Chris

Thanks Chris, I had found and reviewed your pictures earlier.

You're right, the C&C 63" axle will give no trouble with the backing plate flanges, they'll be well back and out of the way.

For what I have in mind I'll keep 8 lug and the bigger and beefier the better, don't want 6 lug. Not sure I quite follow on the difference and advantages of van or truck caliper brackets and such, I do see the different shapes in your parts diagram pictures.
However, are the parts you're using for light truck, what models exactly?
What I have and want to use is from a 2500HD and 3500HD, if that is still "light" at least it's on the heavier end of it.
So we can be sure we're comparing apples and apples what rotor part number are you planning on using?

I considered your Eaton hub idea on the 14 bolt. One downside to me is the increased width, with rotors slid on the outside it'd be about 1-3/4" wider than stock or about 64.75" WMS.
Another complication is I'd want the 9/16" studs, so more machine work. Also the bearings to purchase to make the swap.

Not mentioned yet is the possibility of using the hubs that came on the late model AAM 11.5 axle (or AAM 10.5") that fit the rotors and the rest of the brake parts I want to use.
This won't quite workout because the late model axle spindle is 1/2" shorter than the old 14 bolt. Even if it did swap the WMS would be wider than desired by several inches.
Been looking for any info on other likely late model hubs that would be useful, still 63" axle but larger pilot for the rotor. So far I haven't found even a hint of such a hub.

So, at this point I'm left with the old C&C or dual type hub on the C&C 14 bolt. I would like to mount the rotor on the back side of this held on by the studs same as the drum was originally held on these hubs.
Suppose hub could be machined down so the rotor would slide over it but still there is not a suitable diameter to pilot the rotor. Also results in very slightly wider WMS.

The only real issue thus far in the whole swap is piloting that rotor.

Chris, your comment about about using two flat head screws to center the rotor I suppose with careful machine work is possible, so is drilling and installing dowel pins for same purpose. Originally though those flat head screws did not center the drum, only kept it on the hub, the drum was well centered and piloted by the bore. Relying on those screws to center the rotor means careful machine work would again be necessary with the next set of rotors.

Any more thoughts or ideas?
Am I making too much of a deal about centering the rotors?
If not held in the center (near zero radial runout) won't that cause the wheel, hub, and rotor assembly to be off balance?

Grigg

Here's some mounting info, location of the caliper bracket flange on axle if using the original 2007 rotor, equivalent to NAPA # 86828.

The measurement from original axle is from caliper bracket flange on axle tube to the outside of the hub (because the rotor sips over the hub).
3-15/16" PICTURE
To mount the same rotor on the back side of a hub (like old drums often were) the thickness of the rotor at the flange needs to be added.
0.400" thick PICTURE
So if welding new flanges on the axle tube they should be 4.3375" (or a hair over to 4-5/16") measured from behind the hub flange where the rotor will mount.

To use alternate rotor with smaller bore, NAPA #86830, the math is different.
The rotor is not as tall by 0.177" PIC 1 PIC 2 PIC 3, the difference
The flange is thinner, measures 0.328" PICTURE
4.9375 - 0.177 + 0.328 = 4.0885" or a hair over 4-1/16"

I'm thinking the original rotor in combination with an adapter bushing will be the best solution, so 4.34" is the distance for the flange on the axle behind the hub.

What truck is this brake swap good for?

The late model brakes, and more importantly, the rotor comes from a single wheel pickup. Note that the rotor slips over top of the hub then the wheel is installed.

The brakes as they came on the late model axle will not fit in a 19.5" dual wheel. PICTURE
However, by locating the rotor behind the 14 bolt hub which has a thickness of 1.520" (measured) you gain that much more room.
Here is a picture of this rotor and caliper sititng behind a 14 bolt hub all inside a 19.5" wheel. There is plenty of room. PICTURE
The same in an original 18" dual wheel also fits quite well, no trouble. PICTURE

This swap will also work with a single wheel AD pickup (and many others). Although likely a small wheel won't fit over the 13" rotor and caliper. I have not tested but don't foresee any issues with 19.5", 17", or even 16" single wheels.

Judging by the fit as shown above in a 19.5" wheel which leaves the caliper somewhat below the outer surface of the tire and how that tire/wheel fits the original truck with about 1" clearance between the springs... Indicates there should be plenty of room between the caliper and the leaf spring while keeping the original ~63" WMS.

Should be a good swap for single and dual wheel AD 1 ton trucks (and others) when also doing a 14 bolt axle swap.

Grigg

Today I ordered 4 flanges waterjet cut from 5/8" plate.
They'll come with a bore a little smaller than 3-3/8" so I can bore to suit and face one side leaving a pilot to register the caliper bracket.
Drawing

Sorry it's been a few since my last post.

What I was refering to with the 6 lug... 8 lug rotors, etc... Is specific to van components. Which is what I'm working with. the 03-05 2500 vans have 2 different axle options. Both are semi-float axles. The 8 lug actually being a Dana 60. The both use the same brake caliper bracketry. The only real difference is the 6 lug version has slightly smaller pistons. What I'm planning on doing is using the smaller caliper with the 8 lug rotors. Confusing? Yes. Since the 3600 is quite a bit lighter the the late model van and I can get away with a smaller master cylinder, is why I chose this option.


Anyway, centering the rotor. My plans are to use a couple lug nuts to center and hold the rotor to a hub. Then use the existing holes as a sort of pilot and drill the rotors for the tapered bolt. I know this will need to be repeated anytime the rotors are replaced. How often is that going to happen?

Anyway. Best of luck . Keep up the good work.

Chris

Thanks for the clarification. I don't mind using a larger bore MC to match the larger calipers I have. Good to know there is another smaller option if needed.

At this point I've decided to use the 86828 rotor (came on my 2007 3500HD axle) fit on back of 14 a bolt hub.
This will require a bushing to adapt the approximatly 4.59" hub pilot to fit the approximately 4.83" bore in rotor.
Filling the gap as seen in this PICTURE

You could do the same bushing idea and rotor on the outside of your Eaton hub. Avoiding the countersunk screws. As far as machine work goes the bushing I figure is about as easy, and only have to do it once. I'd also be concerned about shearing the countersunk screws because they would try to take the torque if the studs don't fit the hoes in rotor. I suppose if the lug nuts are snug it might not happen, but it is possible.

Picked up hopefully the last 14 bolt rear axle I'll need today.
PICTURE
This one has the 3.73 gears I want and with luck the gears and housing are in good shape, disassembly, cleaning, and inspection will soon tell.

Grigg

The Bendix brand I have here measures 4.63" which is obviously different than 4.641. The reason the tolerances are so different is that having axial run-out doesn't affect braking on a Disc the way it does a drum. Lateral run out on a drum doesn't affect braking the way it does on a Disc. So a few thousands on a disc to hub fit is not as critical as on a drum. If its to far out you could get a high speed vibration in theory. Disc rotors expand when hot so you do need some room for them to do that on the hub so a .005 fit is not a good thing in this instance.

As for the Right Gear adapters they no longer make the kits and have no idea when they will again. I tried to purchase their cad file because they had no idea when or if they would do these again, but they actually subbed it out and had no file, this was as of last month.

Were I doing the larger bore rotor I would used a centering ring to make it hub centric rather than lug centric but not as close as your thinking.

Rings Link to hub centric rings

Thanks Dave,

I agree that a rotor should be primarily centered for balance reasons and a drum is centered just as much for braking reasons too.

From the 2007 axle/hub/rotor I have the following measurements.

Hub pilot diameter (for rotor) 4.830"
Rotor bore (pilots on hub) 4.834 to 4.835"

This is about 0.004 to 0.005" clearance on what I'm pretty sure are factory parts, not aftermarket or replacement rotors. This is the sort of fit I want and I have no concerns about. Also don't see any problem if the rotor gets warm, expands, and later contracts back to normal.

Thanks for the hub centric ring link, that pretty well illustrates what I've had in mind, we're thinking the same thing here. I want to make them from steel with a light shrink fit on the hub. This will bring the hub I'll be using up to match the diameter of the original hub that fits the rotor I'll use.

The other rotor option suggested, measured at 4.63 to/or 4.64 is still 0.040-0.050" over the 4.59" hub. In my opinion not an appropriate fit without another method of centering the rotor. Judging/comparing by the factory fit of both drums and rotors on their intended hubs with about 0.005" clearance; 0.040" is not close enough to serve the purpose of centering the rotor.
Because a bushing to correctly fit this rotor on the hub would be very thin I've decided to use the rotor with larger bore, easier to make and fit a bushing with a thicker wall.

For what it's worth that's how I see the situation and how I'll deal with it to suit my needs/desires.

Grigg

There is certainly more than one way to skin a cat. We use stud inserts to center up the rotor and that works well for our application and easy for the novice to add discs. It is odd that the rotor bores vary so much between aftermarket makers.

I had missed this write-up, I was building the same thing almost. Got everything but the mounting bracket. How much are the laser cuts costing? I wanted to get more of a registering lip than you have drawn.
Thanks

I'd like to see how your swap is coming along and any troubles you've run into.

Had the brackets waterjet cut, cost me $40 each. Just the shape and holes, I'll turn the pilot. Probably cheaper to have plasma cut but I decided not to, I don't have a local contact for laser cutting so I didn't look into that.
The pilot or registering lip as drawn at 1/8" long is more generous than on the 2007 axle at approx 0.100". It could be longer than 1/8" but I see no need.

Grigg

$40 each is a good price. Who are you using for water jet?

They don't have a functioning webpage, but this is the place.
Waterjet Cutting Inc.
129 Bradley Dr Lynchburg, VA 24501
(434) 847-9000

Here are the flanges, they came out just right and fit perfectly, seems I got the measurements/drawing figured out. There is some slop on the bolt holes (as original) and all 4 studs center nicely in the holes. Outside contour looks good. Inside bore I had leave 1/16" small to be bored to suit later.
PICTURE

What's the plan to get the old ones off and those on the axle and lined up correctly?

The old ones I can leave in place, the Cab & Chassis 14 bolt the original ones are pretty far back. Or torch most of the old ones off and grind to clean up.

For alignment I'll install the hub and tack weld the bracket at correct spacing.
Then with a dial indicator on the hub check and adjust the flange for runout, using hub to swing the indicator around. Finally weld a little at a time still checking runout and trying to weld here and there to reduce runout.

Another idea to help position the new flanges if the old ones remain is to make 4 spacers or use bolts as jack screws in the old flange to help position and align the new flange.

In a similar method to checking the flange with an indicator I thought to first check the axle tube runout where the flange will be positioned and grind or file to true that best I can, then bore the flange to fit this, might help with radial runout. This step might not really be necessary.

Do you have any other ideas?

Grigg

I think I might slide on the flange then put the hub and rotor on, bolt the rotor down. You could then make two rectangular bars that have the correct brake gap measurement and then clamp the rotor, bar and flange all together top and bottom, This way you know its true to the rotor. That sort of what I did on my kit but I leave the old flange in place and weld the new flange on to it. I use the caliper bracket to position it true to the rotor

Also a good idea.
Need to do a little math to figure out how thick those spacer bars need to be.

Any update on this? I have heard of using the late model disc set up on an Eaton using a spacer bolted to the existing backing plate mount to get the proper bolt pattern and caliper alignment with the rotor on the outside of the hub.

No progress on my part, adapting the late model disc with parking brake to a 14 bolt axle.

You’re asking about these brakes adapted to an Eaton axle.
Dave Chapman, now passed, had a kit to do that. His new bracket was just an outline that slipped around and was welded to the original backing plate flange, at least for the 50’s model Eaton many of our trucks have.