3/4 disc brake swap

[plummen]

Fresh meat here with a fresh project.
Ive got a 56 chevy 3/4t pickup i would like to build a dually out of,newer rear axle is a no brainer but im having trouble finding any info about a disc brake swap for 8 lug rotors onto a stock straight axle.
I suppose i can figure out a bearing swap for the rotors,but need ideas for caliper brackets.
I leave myself in the hands of the experts here!

[lmdangerous]

I am not an expert but I am working on my 3800 1Ton JS code pickup truck. The backing plate bolt spacing is the same as the 1/2 ton , so the disc brake kit that speedway , classic etc ( basic kit- brakets,and hrdware- does mot have the hubs etc) sales should bolt on ( around 99$) . I measured the bolt spacing pretty close - even if its off a little -it will be a very close pattern.I plan on grinding the rivits off the brake drum - knock the drum off and that leaves the hub. Late model 3/4 ton 4wd brake rotors slide over the studs. THe basic kit also has the spacers for the backing plates- adjust as needed. Get the mastercylinder adapter bracket(99$) -that bolts to the stock set up - use the MC that is for disc brakes run the lines and you should have them .I have not done mine yet - doing all the work and measurements before I tear it apart. Also have a friend with a spare 8 lug axle ( may use it for a guinepig). I know your truck is a little newer than mine but the basic disc conversion kit that all the companies produce are for a 47-59 chevy -GMC. I would only get the basic kit for the caliper brackets. the rest will be of no use. As for the wheel bearings - there are no tapered rollers available for the 3/4 -1 ton spindle - have checked with every bearing manifacturer out there . As long as it s an American Made bearing -you should have no problems . I have spent about 6 months researching it - Oh yea the standard big GM caliper works with the caliper brackets-means you can find pads, rotors, and calipers , lines etc at any auto store - no special order stuff. Again - I am open to any in put from anyone, more eye, brains, and ideas can only be good - I like the I beam axle -and if the 1/2 ton crowd can have it - so can we. Blackbird also list a disc brake kit for the 14 bolt ,dana , and even the HO 52-72 3/4 ton -1 ton rear. This is all the info I have managed to find - Use at your discretion-I am no expert -
I did the same with a 39 chevy truck using the 1/2 ton 64 chevy van axle( cut to fit) , used 4wd s10 rotors -that slid up on the stock hub stds-after I ground the rivits and removed the drum - The universal caliper bracket at speedway was close - only had to weld and fab a little. The s 10 calipers bolted on,and after we changed the mastercylinder - lines propationing valves -the 39 got the crap run out of it at the drag strip -
LMD

[plummen]

cool,thanks!
i was thinking about trying precision bearing for bearing swap,ive had good luck with them as long as you give them the I.D and O.D your trying to match theyre pretty good at matching sizes

[lmdangerous]

Plummen,
Did you ever contact precision bearing supply? As soon as all this frozen crap is gone I will get a chance to workon it some . Been really cold, and a lot of frozen junk on the ground.
LMD

[plummen]

been waiting on snow to melt,no heat in my barn and im getting domesticated in my old age!

[lmdangerous]

I fully understand. Where are all the global warming people ????? My weather rock does not lie -its been rather cold .

[plummen]

yeah if al gore shows up ill hand him a snow shovel!

[yz465rider]

Just wondering if you guys have found any more info on the disc swap and roller bearing upgrade? -EJS

[lmdangerous]

I have found that tupelo bearing supply has stock replacements . No tapered rollers as of yet. All the info I have found points to the Fact that as long as its a Quality bearing - ( does not speak chinese_) it should be fine - check all the old bearing supplyers( old parts houses) - that are around that still have a lot of NOS stuff. The disc brake brackets from speedway will work - I have a 1/2 ton axle from a 56 , and the bolt( backing plate) spacing with my 3800 axle is identical - so those brackets will work, ordered mine yesterday. I am trying to make up my mind wether to go disc on all 4 corners, or drum back - disc front. Reguardless - I had to go outside of the normal suppliers for the MC bracket - a fellow hamb board member known as ghost rider in newyork built mine- all of the supliers , classic ,lmc, etc were on back order- he put on at my door for 50$- and I can use the corvett MC that I like/ as well as the stock pedals. Weather is getting better - so I should make a little progress.
LMD

[yz465rider]

Thanks! That's a relief to hear the caliper brackets will work, I had everything else figured out except the front brakes. Now I just have to get the factory brakes unseized so I can finally get it out of the field it's been sitting in the last twenty years!

[plummen]

sorry guys been tied up with one of my other expensive hobbys!
since retiring a few months ago ive been working on finding a new building to open a shop specializing in 1973-80 kawasaki z1s/kz 900s-1000s,i also want to work on old chevy trucks and cars and my collection of model A ford stuff.
what can i say im a sucker for anything old and cool!

[philapino18]

I'm also building a disc brake setup for my 3/4 ton truck.
I was looking at 1/2 disc brake conversions, and noticed that they have you split the hub,and sandwich the rotor in it. Is this necessary, or can you just slide the rotor over the hub like they do in modern trucks?

[mr48chev]

Originally Posted by philapino18

I'm also building a disc brake setup for my 3/4 ton truck.
I was looking at 1/2 disc brake conversions, and noticed that they have you split the hub,and sandwich the rotor in it. Is this necessary, or can you just slide the rotor over the hub like they do in modern trucks?

I'm not sure what you mean by "split the hub". On some 3/4 ton rear axle disk swaps the rotor is put on the back side of the rotor with the studs holding it on

I'd do this first, see if you can scrounge up a used mid 70's early 80's Chevy/ GMC 3/4 ton 4x4 front rotor. Borrow one from a buddy or see if the local brake shop might have a bad one in the junk bin. At this time you don't care if it is good or bad as you are just using it for figuring out if the idea will work. Pull the drum off the hub on the truck and slip the rotor over the hub to see how it fits up. Would you be able to make a bracket to hold the rotor to the spindle? A half ton bracket might work if the rotor diameter is the same. Or someone like the guy who made my rear caliper brackets might be able to make you a set if you made and accurate pattern. First you need to figure out how to get the rotor to fit though.

I'd also look at 3/4 ton disk brake hubs for 71/72 and up through the 70/s trucks to see if they can be adapted to your spindle. it might be that finding the right bearings and seal would allow you to make the swap.

[tmoble]

That guy on the HAMB is ghostrider, no space in the middle. He does indeed have a pretty nice looking bracket for the earlier AD trucks. I've asked him about a 55-59 bracket. the earlier style doesn't have the pivot pin mount built in, it's separate. It's easier to build.

[lmdangerous]

I intend on just sliding the late model 3/4 ton FWD rotors , and just sliping them over the studs, use the little clip things that the factory uses and when wheel and all are tightened it can not possibly go any where.This is the plan- I intend on doing this and a engine swap ( 250 late six using the early v8 truck bell housing i machined in my mill rto fit the factory cross member) at the same time . need it back on the road asap -its my only shop truck and this time of year is busy( summer time i get to work on my stuff.) - plus the late model crap i have to drive looks like the guy next doors ride. If any body has any input let it fly you wont hurt my feelings - I just got back from the HOT ROD reunion in bowling green about 2 hrs ago - learned a new definition of the word swim and race at the same time - but it was fun!!!!!!!!!!!!!!!!!!!!!!!

[lmdangerous]

The late model 4wd 1/2 and 3/4 ton rotors are the same diameter according to my parts man. There are different depths according to one old book . (late 88 and up.) The calipers are the same according to my napa guy - remember the late 4wd rotors just slip over the studs like a lot of front wheel drive stuff.Again - i got off my schedule scine the early spring so anyone that has info( corrections / suggestions, etc-more heads means less mistakes , etc- i am open.
MR48chevy - who made your back caliper brackets ??? i heard blackbird interprises did some , but have not had a chance to look \
LMD

[philapino18]

[QUOTE=mr48chev;4743151]I'm not sure what you mean by "split the hub". On some 3/4 ton rear axle disk swaps the rotor is put on the back side of the rotor with the studs holding it on



I went back and reviewed the pics again, and you are right the the rotor goes on the back of the hub. the hub is sandwiched between the rotor and an adapter plate.

Also thanks for your suggestion about using using used parts for mock up, that will save me a bunch of heartache.

I plan to just slide the rotor over the studs. May have to get longer studs, or adjust shims for the caliber, but that is part of the fun, right?

[mr48chev]

This is the same bracket that I bought for the rear axle on my 71 3/4 ton. CNC machined rather than cut and then powder coated. I haven't set the axle up yet but his work is some of the best I have seen. http://cgi.ebay.com/ebaymotors/Chevy...Q5fAccessories

Here is the link to their website http://www.wisnermachineworks.com/
As you would be using the same size rotor you might ask if you could send him an accurate pattern for the hole for the spindle and the bolt holes to mount the bracket to the spindle. you could use one of your backing plates to trace the pattern and get measurements off. The other way would be to have them make the bracket and leave enough material on the spindle end for you to drill the holes but leave you a pilot hole to center the spindle on.

Vusualize this
set up to match your spindle rather than my rear axle.
I'll see if I can get an exact size scan of it in the morning that you might be able to play with.

I'd still find a rotor and then make a pattern out of something that I could work easily. The main thing is that you want to see how the bracket would set on the spindle in relation to the rotor and if the caliper will sit in the right spot.

[lmdangerous]

Nice bracket, You are correct about the caliper spacing . The speedway bracket that they show in there universal kit ( 47 -59 ) shows a set of spacers I figure that different spacers can be used to space the caliper so it sits as it should over the rotor. ( or that is the plan . Again mr48chevy - nice brackets - look sharp compared to the speedway bracket.

[olBlue]

Try these guys for 3/4 & 1 ton roller bearings.

Classic Truck

[lmdangerous]

I got my brackets from speedway bolted on today . It did bolt up as I suspected, and it is not tall enough to clear , or at least let the caliper have 1/4 space on the mounting bolts/ between the rotor .solution - made a copy of the bracket - kind of a blank. - let it overlap - toss the spacers and let the caliper tell me where to weld . I will then drill some extra holes for rosset welds, etc. I had to do this when I put disc on my 39 . I figure that I will mount the rotor and then I will let it tell me where the caliper will need to be . I know that different year rotors have different depths I figure ill start with 1985 or so - unless someone know the depth that will work out - I am all ears.
until next time kids - when I might have the last part of the puzzle soved.
LMD

[lmdangerous]

EUREKA!!!! I have finished it.I even can send a photo album to the editor to post (Hint hint - I cant figure out how to attach them here).
The rotor will actually slide on with no machine work- here is the deal -please don't get shoot me - the rotor that works comes from a FORD E250-350 99-07 van. You will need to make stud spacers ( the factory stud is 1/2 and the rotor holes are 11/16- the studs for the ford actually measured a little over 9/16 .)( machine threaded spacers for each stud or - just drill your hub and install the ford studs( your call) . You could machine a spacer ring for the center of the hub, but I think the spacers( for the studs) will be easier- A and A and Strange offer spacers for that very thing.I can also machine them if I have two - I used the stock lug nuts( tightened ) to center and locate them and it was perfect and true.
The NAPA number on that rotor is 4886799 ( 70$ each ).
The caliper is the standard 85 4whl drive , 3/4 ton front caliper, and pads. All stock stuff no problems -you will be able to use the standard front lines for that truck also.
The bracket set me back 2 weeks of labor / and vacation. It had to be done in a two piece form. I could not come up with a one piece due to the fact that the caliper needed to be spaced to the rotor etc. ( i didnt want a stack of spacers ) - only had to use a 3/8 spacer .
The cross steering rod will have to be narrowed up about 3/4 in, due 2 the thickness of the brackets . Mine will be able to adujust and not be cut -I have about 3/4 of an inch of threads on each end of the tie rod ends.
I have a photo album, but DK what to do to get it here - I have not run the lines or mounted my new master cylinder , but this was the hardest part. The disc brakes for the rearend is literally a bolt on (99$) kit form Virginia 4X4.Uses all 3/4- 4whdrive chevy front calipers , rotors, and lines. I am getting there -
Would be glad to send my photos to the editor , or any one if you get me a email address.
Help me here guys I am close to finishing this , and a lot of you like me like the stock look of the I beam front axle - with brakes that really work!
LMD

[plummen]

Sorry its been a while,this heat wave weve been going through has limited my time outside to turn wrenches.
I did get the truck hauled to omaha so i dont have to make the long cruise down south every time i want to work on it though.
I decided to go the 4x4 route with this project since i came across a mid-80s chevy k20 chassis for a reasonable price,the width on the 2 frames is pretty close so i decided to just mount the 69 cab mounts on the newer frame which i figure will make things easier down the road to find parts if im broke down in middle of nowhere!
the only major differance ive found so far is wheel base from rear of cab to rear axle is longer on newer truck ,but i plan on either installing a shortbox or posslbly a flatbed since i have access to a chevy 1 ton 4x4 dually chassis that was cut up and all the parts were stuck in a barn.
Its got a 14 bolt rearend with a locker,dana 60 frontend with limited slip rebuilt transfer case and t400 trans .eagle aluminum duallies and a fairly low mileage 427 car motor that needs to be checked out,so i think a 69 chevy 1t 4x4 flatbed with 3-4" of lift would be a cool little hauler for pulling home future projects!
I need to finish bolting front cab mounts to frame so i can bolt the body on and start replacing front floor pans and rockers,body was a little rougher once cab was stripped down!

[philapino18]

Imdangerous, Congrats on figuring this out. Are you using a parking brake setup on the rear?

[lmdangerous]

I am using standard 3/4 ton calipers , however the same people that i got the back brake caliper brakets , Virgina 4X4 , and blackbird , both show to use the eldorado caddy calipers if you want a parking brake look -em up.
LMD