The Stovebolt Site Forums The Parking Lot Tons 'o Fun Single wheel AD rear axle swap: GM 14 bolt.

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

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

Grigg

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.

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

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.

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

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.

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

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.

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.

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

Just measured an AD 1 ton:
* Spring centers are 41.5" apart (with the springs as narrow as possible)
* Width outside of springs is 43.5"

Looks like spring pads need to be relocated 3/4" out per side.
Original drums to the axle should just fit around the springs, 3/8" per side.

Someone want to check my measuring on an AD 1 ton?

Thanks,
Grigg

It's cold out there!

These measurements were made on a '54 GMC 1-ton that currently has a 14-bolt in place under it. My pretty much original '54 GMC has enough stuff stacked on it I can't easily measure it now.

I get spring centers at 41.5 inches actually measuring from the near side of the head of one spring bolt to the far side of the other.

I get the outside spring measure as 43-5/8 inches but mine is all bolted together so there is no easy give.

That measurement does not account for the ubolts. I see three or four inches on each side between the springs and backing plates with my wider rear. Since the difference in width is only three or four inches I'm surprised you come up with so little clearance between springs and drums.

With only 3/8ths on a side I'd worry about the the ubolts clearing. If its 2-3/8ths then it should be no problem.

I'll do some more checking.
that clearance is at the edge of the backing plate, there is a little more room in the middle where it's needed, not sure if it's enough room though.
The disc brake conversion kit would solve the problem.
I'll look into using single wheel drums that have less offset/dish and making a spacer for the backing plate (not sure if it's a safe or good idea though?). Might not fit any how.

Grigg

Maybe your measurements will show there isn't a problem.

I was able to find the right Eldorado calipers at Rock Auto. The price for the core is a little high but in the overall scheme of things not huge.

After more checking on the backing plate clearance to U-bolts and springs I find:
Springs should be ~3/8" away from backing plate rim.
U-bolts should have 5/8" room between spring and depressed part of backing plate. (A max 5/8" u-bolt size may fit)
U-bolt nuts and axle saddle should have just enough room because of an extra depression in the backing plate.

I won't say that it'll fit, but it is extremely close and appears that it should, certainly worth a try.

I'll look into swapping for single wheel drum brakes and probably backing plates too.

I'm sure the disc brake conversion will fit.

Grigg

On the one hand I've never been real convinced rear disk made a big difference, but on the other I think I'd convert to disk before swapping to a smaller drum setup.

The 14 bolt Cab and Chassis axle I have has 13" x 3.5" brakes for dual wheels. Drums I think are NAPA # NB 4401652
Napa # NB 4401651 is a single wheel drum with the same brake size.

To use the single wheel brake the backing plate will need about a 1-5/16" spacer between it and the bracket on the axle tube. Which gives this much more room between springs and backing plate.

One problem may be the two different drums in question mount differently. The single wheel drum is intended to slip over the hub, and the dual wheel drum is installed on the hub then the whole assembly is installed on the axle.
I expect that the single wheel drum can be installed first just like the dual wheel one was.

Which leads to another possible solution, and so far I think the best yet.
Use the original dual wheel drum but install it on the outside of the hub. Preliminary measurements are promising. The ID of the drum is 4.5", same as the pilot on the hub for the wheel.
The inside of the drum is machined flat to an 8" diameter, which will accommodate the wheel mounting surface on the hub.
If this works the backing plate needs about 1.75" spacer, and as much room is made between the springs and backing plates.
Added benefit is easy brake work by removing wheel then drum (without removing the entire hub and drum).
A small downside is the wheel gets moved out another 1/4" or so because of the thickness of the drum flange. And note that it's not a problem to loose the pilot diameter on the hub (now used to locate drum) because the single wheels are stud centered (not hub centered like duals)

I've already got a hub and drum off, I'll try swapping drum to the other side.

Grigg

I'm thinking that spacer needs to fit tightly on the axle and be made of some substantial stuff, because the last thing you want is your backing plates moving around and breaking bolts or brackets.

How would you feel about actually welding the spacer to the axle?

Does any of the brake mechanism move into possible contact with the hub as the backing plate moves outward 1.75 inch?

Do you know what year your axle is? I just looked up brake drums for mine on Rock Auto using a '79 P30 as the vehicle and found the same drums used across a number of trucks from '73 to '84. The pictures look like the same drums you found at NAPA, though I don't trust parts dealer photos quite that far.

We are supposed to have temps in the 40's today and I'll try to get outside and look at and measure things. Otherwise I'm back in the hospital tomorrow and away from my toys at least a week.

I agree, the spacers will need to be substantial, probably made from a solid piece of steel.
They will need to pilot off the flange and have a pilot for the backing plate on the other side.

I considered making new flanges, essentially moving the existing ones, but then they really need to be trued up after welding, I don't have a lathe long enough to swing a whole axle housing.

Bolting on the spacers and then welding them to the axle tube seems like a great compromise.

There is lots and lots of room to move all the brake stuff in toward the hub, no clearance problems there.

I don't know what year my axle is. but GM used only a few different hubs and brakes on the 14 bolt, all this stuff is amazingly common and interchangeable. I was guessing 1988 for looking up parts.

Good luck tomorrow and next week, I know what you're going through is no fun.

Grigg

Well slightly off-topic... My expected week's stay at the hospital has been postponed until next week. My mind can now focus (be diverted) again by truck topics.

Well then, while you're focusing and diverting browse through the rear axle pictures so far.
http://rides.webshots.com/album/576070122yffTjF

Grigg

Grigg where did you end up on the brake drum move? Is it workable?

Yes, I haven't made the spacers or looked for studs (might not need different ones)
But I'm sure it's workable, about 1.75" spacer piloted to the old flange and pilots the backing plate to keep alignment.

Grigg

From my experience with 14 bolts, another option may be using the SRW 14 bolt (67" one) with the DRW hubs (either 63" or 72" one). The only difference in these is the location of that flange for the backing plate, the dually hubs vs. SRW hubs are what makes the width difference.

That is the axle I have under my 1-ton project.

I agree, but don't have enough info to know if the dimensions work out.
One of the links in the first post confirms your idea:

So, start with a single wheel pickup axle, swap dually or Cab & chassis hubs (same thing) But, then what brake drums (and backing plates + shoes) fit the backing plate flange already welded to the axle?

Would need a single wheel axle to measure and test fit the different drums.
Or perhaps can figure from just the difference in hubs? here's a picture of single wheel and dual wheel hubs side by side http://www.pirate4x4.com/tech/billavista/14b_bible/images/brawler_hub3.jpg
If the single wheel hubs were traded for dual wheel hubs (on the single wheel axle) then a brake drum with a couple inches less offset/dish/height would be needed as seen in the picture.

If we could find the answer to that problem it may be better than the spacer I've proposed for the C&C axle (otherwise complete with all original parts).

Grigg

I still have that SRW 67 inch wide rear under my 1-ton. I'll measure anything you want that doesn't require taking it apart. At some point I'll be willing to take it apart too, but right now I need it holding up the truck...

Interestingly, and without any intention or effort on my part, I appear to have sold the 72 inch wide Dana 70-HD I have stashed.

I have a friend whom I advised to do this very thing on his Jeep, so he did minus the OEM brakes. I can see if he can take some measurements. He did the same thing as I did for brakes, which is discs with non-parking brake calipers. Thinking about the differences in width, this may put the flange too far out for the backing plates...approx 2" per side...

OK, Can you measure the distance from dual wheel hub WMS to the backing plate flange on the (single wheel) axle?
Then I'll measure the stock setup on the C&C axle to compare that to.
then the difference is how much the drum needs to be shorter, and I can get a good guess in the Napa brake parts catalog if another 14 bolt drum is close.

Thanks,
Grigg

I'll see what I can do. His Jeep is under several feet of snow, so it might take a little while to get the measurements....

Any progress on measurements?

Welll...
I am off to check out the one ton I found on Saturday. I'm pretty interested in hearing the current status on the axle/wheel swap front. Catch y'all with some info about this truck in the next 24 hours!

Jeremy

No progress or time on my end... I expect I'll make backing plate spacers and use the original drum brakes mounted outboard of the hubs.
Other than that and moving the spring pads I think this one's all figured out, but admittedly untested.

Grigg

Grigg,
I'm still green to the Stovebolt page, but I have been noticing the pics you have on the external link in your first post and I'm wondering how the process went for the disc conversion on the original front axle. The pics look like it was quite simple and I'm like to go that route if possible. Let me know what you found and if my original wheels will work with that hub. Thank you for providing so much information, it's invaluable.

-James Keith-

Also, if the disc conversion went well, what are the part numbers?

James,
The front disc brake stuff is discussed in this thread
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=603612#Post603612
Probably best to move discussion of it to that thread so as to not confuse this one.
But in short, just like this 14 bolt swap, I haven't done any more than decide it'll work... But I don't like having to use the expensive original front wheel bearings, and until I find an alternate solution I don't plan to put anything together.
Also, I'm not sure the front rotor and caliper I picked out fit an original 17" wheel, they do fit a 19.5" however.

Grigg

So I've been thinking this axle swap thin over in my head.
I was offered a set of 4.10 axles from a mid 80's 4wd Disc front drum rear.
I am looking for an opinion here and maybe this is silly or I ma missing something but it seems to me that with full floating axles you could simply cut down the axle tubes and the axle shafts to what ever width you need them to be. Then attach your spring perches... and "bob's your mother's brother"
Only reason I came up with that was after looking at Grigg's front axle surgery. Very impressive, and cool but I can't do that and in this state no one I can think of would do it for fear of liability. So I thought running a 4wd front axle without the pinion and I could have a disc front end narrowed to the width I need.
Any thoughts?

Jeremy

That's another method.

As far as front axles go IH, Ford, and Dodge have all used non driven tube type front axles that are essentially 4x4 axles with straight tubes, no differential, and no axle shafts.
A few of my friends have made their own 2wd front axles from 4x4 axles minus the differential.

The big issue with doing that is the ride height, consider that an I-beam axle has usually 2" or more of drop from wheel centerline to spring mounting pad, and a tube type axle has 2" or more rise from center line to pad. That leaves you with a 4" lift just by switching axle design.
Or, if you choose to mount the new axle on top of the springs you reduce your upward axle travel before it hits the frame to next to nothing.

The tube type 2wd front axle swap works well on an already 4x4 truck, but not usually so great on a 2wd truck unless you don't mind the lifted appearance.

Rear axles can be narrowed and new axle shafts made or old ones resplined, this is a lot more work than finding an axle that fits to start with. If it's your only option there is nothing wrong with it, but I'd round up a suitable width axle to start with if there is such a thing.

Grigg

Hmm I didn't think of the spindle to axle height. I don't know that 2" is really all that much considering how tall it sits now. Funny though, Resplining should go ok, I have access to an entire machine shop.
I will think some more. FInding the correct width axle is a trick. 67" seems pretty popular and plentiful If I thought the wheels wuld clear the fenders I'd just leave it alone. I think the tracking of a too wide rear with a stock front coild make the ruck handle even more odd.

Jeremy

It's more than 2" on the front, more like 4", (I-beam to tube axle swap) which will be very noticeable.

Finding the correct width rear axle is not a trick, go back and read the first post in this thread.

Grigg