47-55.1 '52 3800 disc brakes

[milehighjimmy]

I recently started working on a '52 3800 pickup and would like to upgrade the brakes to 4 wheel discs. Along with disc brakes I'm changing over to 6 lugs with a 12 bolt C10 rear for better gearing and an easy disc brake conversion. As for the front I understand a 1/2 ton axle, spindles etc. is a bolt in? To save from changing the complete frontend I was wondering if anyone has ever machined the 1 ton spindles to 1/2 ton dimensions? I don't have any 1/2 ton spindles to compare so I'm shooting from the hip on this one. This truck will never be treated like a workhorse again but just a driver and an occasional trip to Home Depot. thanks

[mr48chev]

There is no percentage in keeping the 1 to axle and spindles if you are going to aftermarket disk brakes. I'd just swap axles and spindles and call it good and you can do the rebuilding before you ever install it.

The GM heritage center vehicle information kit for 52 Chevy trucks has the measurements for both.

This is a list of all the available information kits https://www.gm.com/heritage/archive/...formation-kits

This is the pfd for 52 trucks. https://www.gm.com/heritage/archive/...formation-kits

So far down the page that my scroll finger got a cramp is the info.

[dsraven]

if doing all that work why not just get a 1/2 ton axle that complete, redo the kingpin bushings etc, redo the spring pins and bushings, redo axle mount u bolts, upgrade to the disc brakes for the 1/2 ton spindles, redo the brake hoses and ensure the steel lines are all good front to rear, upgrade the master cylinder for dual circuits and also discs front and rear, install the appropriate brake valving to get the bias correct, upgrade the park brake cables and set up to work with the new rear end, grab a new set of wheels and tires to fit over it all, upgrade the pitman arm if/as requiredand then, when you get that done just after lunch, go for a ride and grab a brewski to show it all off.
i would stick with the stock parts instead of changing a 1 ton axle to accept the 1/2 ton spindles. thats just me though. actually, truth be told, I would upgrade to an IFS but, again, thats just me.

[milehighjimmy]

Looks like its going to take awhile to go thru the GM heritage info. but that should answer a few questions. I'm finding its a bit of a challenge to find 1/2 ton pieces in good usable condition. My original 1 ton frontend, although needing a rebuild, appears to be in better shape than all the 1/2 ton stuff I've seen. I checked on IFS setups but none would retain the stock ride height. I want this truck to look like a stock 1 ton. After reading posts on 8 lug disc conversions it sounds like the bolt spacing for the backing plates/caliper brackets are the same for 1/2 ton and the 1 ton? If this is indeed true machining the spindle diameter to 1/2 ton specs might be an option. Just a thought.

[dsraven]

before doing anything I recommend to check the parts you have to ensure they are free of defects and wear etc. sometimes the old trucks took a good whallop when a youngster was learning to drive or whatever, or you may need a complete rebuild on the kingpins and bushings, spring pins and bushings etc. then i would contact a machine shop with some pics of what you have and what you want to make from it. see if anybody will give you a price and time line. you may want to have the kingpins done at the same time since most guys don't have the tools to install the new bushings without damaging them and also don't have the reamer and guide set to finish the bushings to fit the new kingpins. ask for the all in price on an actual quote so they will include everything they think they will need, shop sundries etc. then do a feasability study on whether it's worth doing all the work and spending the cash on parts and machine work.
there was a fella on the forum who did disc brakes on his 8 lug truck. have you seen that thread?

[dsraven]

will you also swap to 1/2 ton springs for a 1/2 ton ride? that coild change the ride height as well.

[milehighjimmy]

No doubt the entire front suspension and steering will need a little help. I was researching the GM Heritage archive and it shows the spindle diameter at the inner and outer bearings for both 3100 and 3800 but no other dimensions. If. anyone has a 1/2 spindle either good or bad, they would like to sell I could physically compare them for the other dimensions. Thanks

[milehighjimmy]

Just an update on my mission to add 6 lug disc brakes to my 1 ton pickup. I located a 1/2 ton axle and spindles to compare to my 1 ton pieces. If my photos decide to upload it will be much easier to see. There is a lot of similarities between the spindles. The backing plate mounting bolt spacing is identical. Upper bolts are 7/16" and lower bolts are 1/2" on both. The spacing between upper and lower kingpin bosses on the spindles are the same. E ven though the 1 ton spindle uses a larger diameter kingpin the kingpin bore in the 1/2 ton spindle is slightly larger than the 1 ton spindle. Probably due to the thicker floating bushing. About the only thing needed to make a direct swap of the 1/2 ton spindle to the 1 ton axle would be a slightly larger OD bushing to accommodate the ! ton kingpin. Clear as mud?

[milehighjimmy]

more pics.

[dsraven]

custom steel bushing in the 1 ton axle to accept the 1/2 ton kingpin?

[mr48chev]

Looking at this again and pondering the machining thing. I'm going to say that depends 100% on if you have the equipment or access to and the skills to accomplish the task rather than pay someone in a job shop to do the work.

Being able to do such a project yourself or have your buddy with the machine shop in his garage who gets involved in your project do it is one thing. Going out and paying today's machine shop labor and setup charges to have it done is totally different. The last piece I had done in a machine shop was a pretty simple machined for bearing fit and broched for a key for sprockets on each end shaft but There was a couple of extra fees on top of the actual labor costs. The Machine work including setting things up took less than a half hour but by the time shop fees and minimum fees were added in it cost about an hour and a half's worth of time plus the price of the shaft.

[1project2many]

These are great pictures. Thank you.

1/2 ton trucks use a floating king pin bushing while the 3/4 ton trucks use a pressed in bushing. I haven't found bushing OD specs but it definitely appears the 1/2 ton spindle has a larger hole than the 3/4 ton spindle. Is that a 1/2 ton kingpin bushing I'm seeing in one of the photos? The one with the groove around the OD? Maybe you could measure the OD?

GM lists the 3/4 ton kingpin at .921" diameter while the 1/2 ton is .866." I definitely think a metal sleeve could be used to take up the space between the OD of a 3/4 ton bushing and the ID of the 1/2 ton spindle. Or maybe it will turn out that the spindles are closer in diameter than they appear?

Do you have a plan for the disc conversion once the spindles are installed? The 88-99 GMT400 trucks use a "hat" style rotor. The ID of the rotor pilot is approximately 3.1" while the pilot on the '57 3100 hub is approximately 3.5" OD. I would think a guy with a brake lathe could set up the hubs and turn down the pilot to fit the later rotors. If your master cylinder has the capacity you could match a '98 K1500 rotor up to a 98 K2500 caliper to get greatly improved disc braking. The big trick is making caliper brackets.

Good luck!

[dsraven]

if the plan is to use a 1/2 ton spindle then cleaning and reaming the axle kingpin hole, to ensure it is round etc, and having a new steel bushing/sleeve pressed into the 3/4 ton axle would be what I would do. you may end up swapping out a few other things as well, like the pitman arm, but that would be because it is worn out or because the length would be different than the 1/2 ton. if you lower the truck that also changes the pitman arm relationship to the steering spindle connection.

[milehighjimmy]

My preference doing this conversion would be machining the 1 ton spindle to accept any available disc brake setups offered for 1/2 tons. That would also allow all other front end parts to be stock 1 ton pieces without custom bushings, bearings or anything else. Today i found a local machine shop willing to machine the 1 ton spindles to 1/2 specs for a very reasonable fee. With the spindles having 1/2 ton dimensions for bearings and brakes I should be able to purchase a 6 lug disc brake conversion from any of the various vendors. The machinist said this should be very straightforward. We will see

[dsraven]

Without reading back through I assumed that you meant the 1/2 ton spindles were basically the same as the 3/4 ton except for the kingpin size and the spindle size. The backing plates are the same bolt pattern etc. It would make more sense to me to simply have a steel bushing pressed into the 3/4 axle that is already in the truck. Then install the rebushed 1/2 ton spindles. Any brake upgrade would be based on the 1/2 ton spindles then. To machine a length of steel bushing to fit the axle and roughly fit the 1/2 ton kingpin (it would need to be precision teamed as the new 1/2 ton spindle bushings would, so that could be done at the same time by yourself. Just gotta buy the reamer and guide) and then cut that bushing into 2 pieces, one for each side, has got to be cheaper and quicker than machining both 3/4 ton spindles.
Did I miss something?

[dsraven]

sorry, I meant 1 ton spindle. anywhere I said 3/4 ton I meant 1/2 ton.

[dsraven]

I bought an adjustable reamer and the guide that helps ensure the reamer stays parallell between the 2 bushings and it didn't break the bank. the old spindle bushings can be punched out of the spindle using a chisel if you don't have a driver or a socket that will do the job. I usually use a punch on an air chisel to remove a groove in the bushing and thereby weaken the bushing and then a socket to push it out. clean the bore and press in a new bushing in the vice if no press is available. I don't like to hammer a new bushing in because they get mushroomed easily. once thats done then the reamer comes out and a few passes are done until the new kingpin fits well. the same reamer could be used on the axle to fit the kingpin to the new bushing installed in the 1 ton axle.
gotta be cheaper and faster at the machine shop to simply punch out a bushing to fit the axle kingpin bore.
brothers has a youtube on rebuilding the kingpins
https://www.google.com/url?sa=t&sour...4SKbbX2dyyKE72

something like this for an adjustable reamer with the pilot set
https://www.amazon.com/2-Tool-Adjust...14&sr=8-4&th=1

[mr48chev]

The more I get into this the more confused I get. When you look at this the OK of the 3800 king pin bushing is smaller than the OD of the 3100 bushing even though the 3100 king pin is .055 smaller in diameter. I don't think that there is enough brass inside the 3100 bushings to hone out .055

To me it just makes more sense to swap the whole axle and spindle if he doesn't machine the spindles to the smaller diameter.