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Single wheel AD rear axle swap: GM 14 bolt.
#599879 Thu Dec 10 2009 03:24 AM
Joined: May 2005
Posts: 9,176
G
Grigg Offline OP
.
Edit Pictures of this project are in, and will be added to, this album: http://rides.webshots.com/album/576070122yffTjF

Another idea for axle swaps, so far the best idea I've found.

I just purchased a GM corporate "14 bolt" rear for my single wheel AD 1 ton pickup, comes with 4.10 gears which I think is perfect for a 235 in a 1 ton.

Faster and slower gears are available too.

Lots of 14 bolt info here
More here with a link to the service manual

The version to look for is from a truck sold as a cab and chassis, like a truck with a service bed, or some step vans, what ever it is it'll have dual wheels.
This will have drum brakes, but inexpensive disc brake caliper bracket kits are available to use factory Chevy truck parts.

The dual wheel C&C axles have approximate 63.5" Wheel Mounting Surface to WMS measurement.
The stock axle from my 52 1 ton has a 62.625" measurement, so if you can live with the (single) wheels each sitting about 7/16" further out it'll work just fine.

You don't want a dually axle from a pickup truck, they are about 72" from WMS to WMS = to wide.


What I don't yet know is if the really big drum brakes will fit or if they hit the springs, what's the distance between backing plates?

The hubs will stick out about 4", not sure if this fits under the stock hub cap?

Don't know about spring center spacing, but perches can be cut and welded to fit and to correct pinion angle if needed too.

Drive shaft U-joint will fit, same Spicer 1350 series, don't know on drive shaft length?

Just for info the stock front axle measures approximately 58.25" from WMS to WMS. I'll be researching and fabricating some sort of disc brake or complete axle conversion before to long. So many people talk about it but very few if any have actually done it for a single wheel 1 ton? So for now add me to the list of folks that talk about it, hopefully I can one day be removed from that list wink

Axle should get here in time for Christmas, I'll do some more measuring, calculating and posting then.

Grigg

Last edited by Grigg; Mon Dec 28 2009 03:24 AM.

1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: Single wheel AD rear axle swap: GM 14 bolt.
Grigg #599924 Thu Dec 10 2009 04:34 AM
Joined: Oct 2003
Posts: 5,161
O
Cruising in the Passing Lane
Short answer is that the drums clear the frame on a 1-ton by a more than adequate margin. Maybe tomorrow I'll measure it for you, but tonight its in the 20's out there and I'm too comfortable to get that cold.

A poor picture.

This is the axle under my '54 GMC 1-ton. It has 3.42 gears and the pads appear to have been moved. I got this rear under a '50 Chevy 1-ton so I don't actually know where it started life. There appears to be two versions of the internals or bearings depending on when the axle was made. One of these days I need to figure how which I have.

I believe the wheels on it right now are 15 inch, though they could be 16s. They are only rollers. There is plenty of room around the drums for brakes.

The cheaper disk conversion kits do not include a parking brake, so that's something to think about when choosing parts for a conversion.


Its true, I really don't do anything but browse the Internet looking for trouble...
Steve@OldSub.com . www.OldSub.com . www.MaxwellGarage.com . www.OldGasTowRigs.com
'55 1st GMC Suburban . '54 GMC 250 trailer puller project. '54 GMC 250 Hydra-Matic . '54 Chevy 3100 . '47 Chevy COE . and more...
Re: Single wheel AD rear axle swap: GM 14 bolt.
OldSub #599976 Thu Dec 10 2009 01:26 PM
Joined: May 2005
Posts: 9,176
G
Grigg Offline OP
.
Originally Posted by OldSub
The cheaper disk conversion kits do not include a parking brake, so that's something to think about when choosing parts for a conversion.

Correct, but if you use expensive late 70's Eldorado calipers they have parking brake.
I'll be running an SM420 with drive shaft brake at least for now.
And if you say the drums fit as is I'll run them to start with till I figure a front disc brake setup to match the available rear setup.

Does the axle in your picture measure 63.5" from WMS to WMS?
Looks like a "first design" 72-88 model by the lack of ribs on top (from info in first link in first post)

Grigg


1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: Single wheel AD rear axle swap: GM 14 bolt.
Grigg #600103 Thu Dec 10 2009 11:04 PM
Joined: Oct 2003
Posts: 5,161
O
Cruising in the Passing Lane
Originally Posted by Grigg
Does the axle in your picture measure 63.5" from WMS to WMS?

That's what I would have said, but I just now braved the cold to measure it and discovered its 67 inches. The axle has been under there since Thanksgiving of '08 so its been a while since I last measured it.

There are 4-3/4 inches between the backing plates and the springs and closer to 8 inches between the backing plates and the frame.

Subtracting half of 3-1/2 inches from each side I believe you'll have plenty of room.

It may be that if I tried to put a standard box on this truck I'd have a tire interference problem. Since I've not been able to find one its not an issue.


Its true, I really don't do anything but browse the Internet looking for trouble...
Steve@OldSub.com . www.OldSub.com . www.MaxwellGarage.com . www.OldGasTowRigs.com
'55 1st GMC Suburban . '54 GMC 250 trailer puller project. '54 GMC 250 Hydra-Matic . '54 Chevy 3100 . '47 Chevy COE . and more...
Re: Single wheel AD rear axle swap: GM 14 bolt.
OldSub #600711 Sun Dec 13 2009 01:00 AM
Joined: Aug 2005
Posts: 114
P
Wrench Fetcher
Grigg,

Do you have a source for disk brake conversion brackets for a Dana 70 Dually axle?

Also, where can you find those elusive late 70's Cadillac Eldorado Calipers with the parking brake parts in them?

I'd like to update my Dana 70 rear with Disks to match the Dana 60 front axle. I haven't done anything with it yet as I'm still looking for parts.

Lane

Re: Single wheel AD rear axle swap: GM 14 bolt.
Photo #600715 Sun Dec 13 2009 01:38 AM
Joined: May 2006
Posts: 8,490
L
Master Gabster
How about using the rear disks from a late model 1 ton? The parking brake on them is built into the backing plate, and uses the hat section of the rotor as a drum, just like the Corvettes. They also use a far superior caliper design to the failure prone actuated caliper type (trust me, I've replaced enough of them to know). You could probably snag the entire setup reatily cheap at any salvage yard.


Bill Burmeister
Re: Single wheel AD rear axle swap: GM 14 bolt.
Photo #600897 Sun Dec 13 2009 04:52 PM
Joined: May 2005
Posts: 9,176
G
Grigg Offline OP
.
Originally Posted by Photo
Grigg,

Do you have a source for disk brake conversion brackets for a Dana 70 Dually axle?

Also, where can you find those elusive late 70's Cadillac Eldorado Calipers with the parking brake parts in them?

Don't know about brackets for a 70 rear, lots of Dana 70's came with disc brakes, don't know if they are interchangeable with an originally drum brake axle, but worth looking into?

For brackets for these 14 bolts I'll go to
http://www.tndiesel.com/
Scott is quite helpful, even sold me the axle I'll use.
Here's a thread showing his complete disc conversion with parking brake calipers too.
http://www.4btswaps.com/forum/showthread.php?t=11387

I've seen new calipers listed online for around $300 outright, just search, not sure what Scott's price is and if they are new or rebuilt?

Obviously if you don't need the elusive caddy calipers the regular Chevy truck ones are lots cheaper.

Grigg


1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: Single wheel AD rear axle swap: GM 14 bolt.
Grigg #600918 Sun Dec 13 2009 06:30 PM
Joined: Jan 2008
Posts: 4,740
C
'Bolter
I recently measured the rear end under my 2009 Chev 2500HD. It is disc brakes, 3.73 posi and all the dimensions are close enough to my 1950 GMC 3/4 ton so that I could easily swap. Even though I'm not very active in the salvage business any more, I still watch what salvage brings. Hard front hit 3/4 tons with single tires don't arouse much interest. Of course this doesn't mean a salvage dealer will sell the rear cheap if he knows you really want it.

Re: Single wheel AD rear axle swap: GM 14 bolt.
Grigg #600939 Sun Dec 13 2009 08:34 PM
Joined: Oct 2003
Posts: 5,161
O
Cruising in the Passing Lane
Originally Posted by Grigg
Scott is quite helpful, even sold me the axle I'll use.
Here's a thread showing his complete disc conversion with parking brake calipers too.
http://www.4btswaps.com/forum/showthread.php?t=11387

That was an interesting thread. I sometimes think of joining that forum because they talk about things I'm interested in beyond the Diesel stuff.

Just one comment in regards to Scott's defense of driveline brakes. While I have never broken both driveshafts (I have broken one) I once split a transfer case in two in such as way that neither driveline recieved power from the motor. The vehicle was dead where it sat with the front axle in a ditch that was hidden by snow.

There was no threat of it rolling, but a transmission mounted driveline brake would not have held it. An axle or transfer case mounted brake probably would have.

This was a '70 Blazer (in about 1980) that I'm sure used the rear service brakes for emergency brake. I've owned several four-wheel-drives since, but my wild off-roading days are long in the past.

My point is that we want to be smart about things like disk brake conversions, but that there is a practical limit to how much we can protect ourselves.

Copying the design of a modern factory system is probably going to offer the best engineered and likely safest choice. However that's hard to do on the front of our trucks unless you go with Grigg's narrowed axle approach.

Be smart and be careful. When you do something different than the factory be sure you know why it works and why its better and what its limitations might be.


Its true, I really don't do anything but browse the Internet looking for trouble...
Steve@OldSub.com . www.OldSub.com . www.MaxwellGarage.com . www.OldGasTowRigs.com
'55 1st GMC Suburban . '54 GMC 250 trailer puller project. '54 GMC 250 Hydra-Matic . '54 Chevy 3100 . '47 Chevy COE . and more...
Re: Single wheel AD rear axle swap: GM 14 bolt.
Grigg #604103 Thu Dec 24 2009 06:06 PM
Joined: May 2005
Posts: 9,176
G
Grigg Offline OP
.
Originally Posted by Grigg
The dual wheel C&C axles have a 63.5" Wheel Mounting Surface to WMS measurement.
The stock axle from my 52 1 ton has a 62.625" measurement...

What I don't yet know is if the really big drum brakes will fit or if they hit the springs, what's the distance between backing plates?

The hubs will stick out about 4", not sure if this fits under the stock hub cap?

Don't know about spring center spacing, but perches can be cut and welded to fit and to correct pinion angle if needed too.

Axle should get here in time for Christmas, I'll do some more measuring, calculating and posting then.

Grigg

Well, it's almost Christmas and I just unloaded and measured the new axle.

Findings are:

* Actual measurement from WMS to WMS is 62.75"
* Room between the backing plates is 44.25"
* Hub sticks out about 3" from the hubcap mounting surface in the center of the 19.5" wheel I have to measure, pretty sure the stock dished cap won't fit. A little later model front 4WD front cap may fit and leave the hub poke out some.
* Spring center distance is 40"


Grigg



1951 GMC 250 in the Project Journals [stovebolt.com]
1948 Chevrolet 6400 [stovebolt.com] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup [stovebolt.com]
---All pictures [picasaweb.google.com]---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
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