73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: 84Silverado4x4 on April 03, 2020, 10:23:24 PM

Title: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 03, 2020, 10:23:24 PM
I have an 84 chevy k10 SCSB that could use better braking.  I'v been using it as a daily driver for the last 6 years or so and have made a lot of changes and a few have made things a little better but still not what I think they should be.
Here is what I have:

84 K10 Born a 305 with power disc in front.  I assume the booster and master are correct for what it came with factory.
Truck has a 4" lift and extended braided front brake lines have been added.
Front and rear axles are off an earlier truck.  73-76  I think.  Front is a Dana44 with stock disc and I have replaced the pads and rotors and bled them.
The rear is a 12 bolt with new drum hardware.  It seems adjusted good but I know I have to apply pretty good pedal to get the rears to do much.

Lastly  The truck is equipped with a 5.3 vortec I installed from a 2006 chevy pickup and it is all stock and should provide plenty of vacuum.  Wheels are MT Classic III's 16x10 with some cooper A/T 35" tires.

Do I have a bad combo in there or is there something a should change to improve things?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: VileZambonie on April 04, 2020, 04:59:17 AM
What needs to be better specifically? ASSuming you've checked everything thoroughly at each wheel, have you checked the brake booster? When the booster stops lending a hand the pedal will require much greater effort.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 04, 2020, 09:13:22 AM
It's a little hard to determine exactly.  There is decent power from the booster and the truck does have brakes but it just seems weak.  Like even when you press really hard they don't really want to lock up and the front just kinda groans.  They work ok for average stops but not good in a panic situation or if I have any additional weight on the truck like towing a trailer it just wants to push through.  The rear drums seem like they are adjusted properly and any tighter it would drag but I have to be using about 95 % of my pedal range to get them to do anything.  If I am on ice and I go from park to drive I have to really stand on the brakes to keep the rears from wanting to spin.  It seems like my fronts are weak and they are doing 95% while the drums are doing 5%.  I didn't know if maybe my 1984 booster, master, and proportioning valve are not properly matched for my 1973 axle brakes?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: VileZambonie on April 05, 2020, 08:32:14 PM
I would advise you go through the whole system with a fine toothed comb. Recheck everything and if you can't stop on ice, master/booster is in order.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on April 06, 2020, 03:20:05 PM
I don't think the proportioning valve is miss matched, but I would suspect it is NOT proportioning correctly. Is it connected to the indicator light?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 06, 2020, 09:52:35 PM
I have Dakota digital VHX gauges in the truck and I do not have any of those brake indicators hooked up.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: ehjorten on April 07, 2020, 09:08:51 AM
One of these makes diagnosing braking issues much easier!
https://leedbrakes.com/p-33765-leed-brakes-brake-pressure-gauge-kits.html (https://leedbrakes.com/p-33765-leed-brakes-brake-pressure-gauge-kits.html)
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 07, 2020, 10:24:33 PM
I think I have one at the shop.  what should front and rear pressure read?  Also if I decided to throw some new calipers on the front is there another option that would perform better? Like JB6/JD6 - 11" - 2-15/16" piston diameter caliper VS. JB7/JD7 - 13" - 3-5/32" piston diameter caliper?  I know I could always look towards an aftermarket company for brakes but I can't imagine I can't get decent brakes from OE parts but if I'm buying new anyway maybe there is something better to put on?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: ehjorten on April 08, 2020, 08:56:10 AM
You should be able to stomp on the pedal and get at least 800 psi.  Under severe braking you would want to have maybe as much as 1,200 psi.  But really, what you are looking for is an imbalance, that would point to a circuit that isn't building pressure.  Then you need to systematically troubleshoot to find what components or components are causing the issue.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on April 08, 2020, 10:23:18 PM
Test the proportioning valve's electrical state:

Use a volt omh meter and test continuity between that connection tang and the chassis. If there is continuity, the valve needs adjusting if you posses the knowledge and ability, replacement if you don't.

Throwing new parts on the ends of the circuits is the last thing to do.
Title: My 84 K10 could use better brakes..What should be done?
Post by: roundhouse on April 11, 2020, 10:20:14 PM
Have you replaced the drums with high quality not made in China drums ?
New high quality shoes ?
    Do the parking brakes work good ?

Replaced the calipers with high quality new, not rebuilt ones ?
New quality  pads ?

The master cylinder with a quality new not rebuilt one ?

Most of the pedal feel comes from the rear drums , while most of the actual stopping power comes from the front brakes.
If the rear brakes are not adjusted properly your pedal will drop a long way before it does anything

And lastly you may have to add in a aftermarket adjustable proportioning valve

We had to install one on ours
The factory prop valve just would not work right .

I adjust the rear brakes by turning the drum and using a brake spoon or screwdriver to click the star wheel two clicks  at a time until you can hear the shoes scrape the drum

Then if everything is working properly they will self adjust when you back up and apply the parking brake

You donít really need them to lock up on pavement


But you can test them on dirt to see which wheels are locking up first , showing you which wheels are not providing enough brakes.

Also bleed them using a vacuum bleeder or a power bleeder that forces the fluid through the lines

If you have a tiny air bubble anywhere in the system is will take away a lot of braking power
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 11, 2020, 11:32:39 PM
Test the proportioning valve's electrical state:

Use a volt omh meter and test continuity between that connection tang and the chassis. If there is continuity, the valve needs adjusting if you posses the knowledge and ability, replacement if you don't.

Throwing new parts on the ends of the circuits is the last thing to do.

I had time to test for continuity and there was none.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 11, 2020, 11:52:43 PM
Test the proportioning valve's electrical state:

Use a volt omh meter and test continuity between that connection tang and the chassis. If there is continuity, the valve needs adjusting if you posses the knowledge and ability, replacement if you don't.

Throwing new parts on the ends of the circuits is the last thing to do.


I had time to test for continuity and there was none.

Have you replaced the drums with high quality not made in China drums ?
New high quality shoes ?
    Do the parking brakes work good ?

Replaced the calipers with high quality new, not rebuilt ones ?
New quality  pads ?

The master cylinder with a quality new not rebuilt one ?

Most of the pedal feel comes from the rear drums , while most of the actual stopping power comes from the front brakes.
If the rear brakes are not adjusted properly your pedal will drop a long way before it does anything

And lastly you may have to add in a aftermarket adjustable proportioning valve

We had to install one on ours
The factory prop valve just would not work right .

I adjust the rear brakes by turning the drum and using a brake spoon or screwdriver to click the star wheel two clicks  at a time until you can hear the shoes scrape the drum

Then if everything is working properly they will self adjust when you back up and apply the parking brake

You donít really need them to lock up on pavement


But you can test them on dirt to see which wheels are locking up first , showing you which wheels are not providing enough brakes.

Also bleed them using a vacuum bleeder or a power bleeder that forces the fluid through the lines

If you have a tiny air bubble anywhere in the system is will take away a lot of braking power

The rear drums are set up with high quality parts and have been bled as well as adjusted.  The truck was missing the parking brake cables when I purchased it and with an auto I have never taken the time to install new.

I should also state that I restore classic cars for a living and install brakes on a lot of vehicles so I'm fairly familiar with most aspects. 

The pedal feel is actually pretty normal in my opinion.  The booster is working like it has good vacuum and with a stock modern 5.3 Vortec engine I have no reason to believe there is a problem there.

I have bled the fronts and replaced rotors and pads.  The truck is lifted and has extended braided brake lines.

The brakes feel good enough to drive it as I do daily but I don't think the rears are doing their part even though they are adjusted properly and the front could be improved.  I changed to a lighter wheel and tire combo recently and shaved over 22 lbs per wheel and tire off and it definitely helped but not as much as I'd like.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on April 12, 2020, 08:22:56 PM
Ok, now you have my attention: What type of classics do you restore?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 13, 2020, 07:35:45 AM
The name of our shop is Muscle Car Creations and we specialize in 60's and 70' muscle but we will restore just about anything.  I try to stick to American Made stuff.  Almost every vehicle we do gets a brake job and we are starting with all new parts usually using one of the big name companies.  The bulk of them get 4 wheel disc and the high horsepower stuff will get Hydroboost and most systems use and adjustable proportioning valve.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: MIKE S on April 13, 2020, 10:48:17 AM
Is the brake booster a single of dual diaphragm? If its single and you have the original master cylinder then it was set up for 10x2 rear brakes. you say you have a 73-76 rear axle. That should have 11/5.32x2 3/4. shoes. Wheel cylinder could be a mismatch if thats the case. I would put a dual diaphragm booster and match the master cylinder to the rear brakes and see if that would help. Smaller diameter wheel cyl will give higher and stiffer pedal but less force. Larger diameter will give more force but lower and softer pedal. 
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 13, 2020, 12:42:26 PM
I'll check my booster and measure the rear brakes.  I know the front axle is a dana 44 and it has the smaller spindle with the smaller hub and bearings.  I also replaced the tie rod ends at one time and discovered that required a set meant for a 73.  I don't know the year of the rear axle but I know it's a 12 bolt half tone and I assumed it was somewhere in the 73-76 range like the front axle. 

I did a small test this morning and I could get the fronts to lock up at a 5mph roll on both gravel and asphalt.  The rears aren't doing a thing.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 14, 2020, 10:28:38 PM
I think I may have found the rear axle date code.   I came up with a J204 on the top passenger side of the center section on the housing on the front side.  Would that be October, 20, 1974? 

I should look for the front axle code also just so I know.  Where do I find it one a DANA 44?

Also are there obvious differences on the Boosters to know what I have?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: MIKE S on April 15, 2020, 08:11:11 AM
The obvious difference is the single is fairly flat while the dual is pretty thick. Check out some of the under hood pictures of members rides and you will see the difference.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: VileZambonie on April 15, 2020, 10:56:00 AM
http://forum.73-87chevytrucks.com/smforum/index.php?topic=16967.0
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 15, 2020, 12:23:54 PM
I would say my booster looks like the tandem or dual booster and my master cylinder is an aluminum one with a plastic reservoir tank with a black plastic lid.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: MIKE S on April 15, 2020, 03:40:03 PM
Then I would probably try a wheel cylinder with a bigger bore. Unfortunately you will probably have to take yours apart to determine the size. You could have been given the wrong size cylinders to begin with.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: bd on April 15, 2020, 05:56:14 PM
When a booster fails, all of the brakes are affected, not just front or rear.  I can't stress enough to reverify the basics.  84Silverado, your descriptions have consistently suggested the tiniest bit of air trapped in the hydraulic circuit pressurizing the rear brakes.  Have you performed a gravity bleed?  How, exactly, did you adjust the rears?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 15, 2020, 08:19:23 PM
When a booster fails, all of the brakes are affected, not just front or rear.  I can't stress enough to reverify the basics.  84Silverado, your descriptions have consistently suggested the tiniest bit of air trapped in the hydraulic circuit pressurizing the rear brakes.  Have you performed a gravity bleed?  How, exactly, did you adjust the rears?

I don't think that I have any failing parts per say.  I know I need to dig back into the rear and investigate.  I just didn't want to waste my time trying to fix something that may not be able to be repaired if I had a mismatch of parts on the truck.  In my years of restoring cars I know its very important to have everything working together and sized accordingly. 

All bleeding was done using a Phoenix bleeder and then done again with manual bleeding pumping the pedal.  Rear brakes were adjusted so there was the slightest amount of drag on the drums. 
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: bd on April 15, 2020, 09:06:27 PM
Really, my point is, and I think you'll agree, to discover the cause of the symptoms before dumping any money into it.  That way, you can upgrade however you wish without being disappointed in the end. 

I recommend, for chagrins, that you back off the parking brake on both sides until the shoes are visibly fully seated against the respective anchor pins.  Then try tightening the self-adjusters until the drums won't spin by hand.  Back the adjusters off 10-12 "clicks."  At the same time, perform a gravity bleed being careful to ensure that the master cylinder remains full of fresh DOT 3 fluid.  Finally, recheck brake system performance to see if there was any gain. 

Does the vehicle have a load proportioning valve?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: MIKE S on April 16, 2020, 10:43:10 AM
Another thing to consider is the brake shoe material. I put a couple of different generic part store rear shoes on my 87. Could not get them adjusted right and just didn't have the right feel. Found some A/C Delco shoes and it made a substantial difference. You could see the difference in the brake shoe material. Also way back these trucks used asbestos in friction material. Now you have metallic which needs to be hot to work properly and ceramic along with various other materials. If the frictions are not balanced like it was when new then that could be part of the problem.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on April 25, 2020, 04:11:35 PM
I finally had time to dive into the rear brakes and investigate.  I started by bleeding the brakes again and I had zero air in the system and still no rear brakes.  I took things apart and the rear axle is date coded 74.  The brakes measure correctly for that with the 11 5/32" drum and 2 3/4" shoes.  I want to completely replace the rear brakes and have everything new either with the correct wheel cylinders and the rest of the drum assembly or go to a disc brake conversion. 

Anyone have any suggestions for me?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 03, 2020, 10:16:59 AM
As I took the rear brakes apart The shoes and hardware still looked like new but the drums had a ridge in them and couldn't be turned.  I decided to just start over with everything new.  I bought new drums, shoes, wheel cylinders, and a hardware kit.  I swapped all the parts out and adjusted and bled the drums with the brakes performing exactly the same.  If I have the rear up on jack stand and running in gear and stomp on the pedal as hard as possible it will just slow the rear wheels down.  I'm just not getting enough fluid/pressure to the rear wheel cylinders.  My thoughts are the proportioning valve must be the culprit but I don't know if I should replace it with a factory one or just swap in an adjustable style.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: ehjorten on May 03, 2020, 01:19:19 PM
I don't remember all the details in this thread, but did you replace the flexible line from the frame to the axle at the rear?  I know you said you replaced drums, hardware, shoes, slave cylinders, but you didn't mention the flexible line in your last post.  Could be a flap in it that is restricting pressure.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on May 03, 2020, 05:07:39 PM
Yes the flex line could be the prob!

I learned the hard way: changed out the caliper, same prob.

It happened after I did a seriously hard break with full toy house 5th wheel.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 03, 2020, 09:22:50 PM
The flex line in the rear looks like it had been changed out recently before I bought the truck but it is just a factory style line.  What happens to these lines to cause issues?  I looked up some stuff regarding the proportioning valve and the symptoms listed sounded exactly like what I have going on.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: ehjorten on May 04, 2020, 09:14:57 AM
You can sometimes get a flap of material that comes loose inside the flex line that will "flap" over the opening and restrict fluid flow.  Your proportioning valve could be the culprit though.  Have you tried pushing the reset button at the front of the valve?  There should be a rubber bulb at one end of the proportioning valve.  If the system becomes unbalanced and the valve travels to one side, that button lets you push the valve back into position.  Sometimes the valve can be difficult to get reset and you will need a tool to help you move it.

Here is a decent troubleshooting guide: https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop (https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop)
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 04, 2020, 09:43:43 PM
You can sometimes get a flap of material that comes loose inside the flex line that will "flap" over the opening and restrict fluid flow.  Your proportioning valve could be the culprit though.  Have you tried pushing the reset button at the front of the valve?  There should be a rubber bulb at one end of the proportioning valve.  If the system becomes unbalanced and the valve travels to one side, that button lets you push the valve back into position.  Sometimes the valve can be difficult to get reset and you will need a tool to help you move it.

Here is a decent troubleshooting guide: https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop (https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop)

Thanks!  Maybe I should try replacing the rear flex line before I go farther?  I have checked the proportioning valve reset but it seems that it is already in the correct position and I was thinking that the end where that is deals with the front brakes.  I have tested for continuity and also with a test light like the trouble shooting article showed with no luck there so maybe there isn't a problem with the proportioning valve?  I have also tried stomping on the brakes very hard multiple times as I read that could reset the valve but haven't had any luck at all.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on May 04, 2020, 09:58:53 PM
Getting closer...
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 05, 2020, 07:34:19 AM
Getting closer...

Hopefully!  With my luck the last piece I try to replace or repair will be the culprit and I will have made the entire system new in the process lol!
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: JohnnyPopper on May 05, 2020, 04:24:54 PM
Yeah, like finding a lost item "the last place you look"!

Hope this is over for you soon... :o ;)
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: roundhouse on May 16, 2020, 09:01:16 AM
I like the adjustable proportion valves
They are nice if you have larger tires etc
Iíve even used two of them on the back axle to be able to balance each wheel
I once had a truck with 35 inch tires and a 14 bolt 3/4 ton axle and we replaced everything, lines, wheel cylinders, shoes, drums , hardware etc and the right rear always locked up first
We finally installed an adjustable prop valve on the axle for each wheel to solve it


Iíd also replace the flex line

If a new flex line doesnít solve it Iíd get a pressure gauge made for brake systems

And start by hooking it to line at the wheel cylinder, then hook it to the end of the flex line
Then hook it to The front of the flex line and So on at every junction till you isolate the problem
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 17, 2020, 04:16:26 PM
Well I spent some more money and didn't get anywhere.  I replaced the rear axle flex hose with a skyjacker braided hose and I also replaced the rear axle hard lines since that was pretty cheap and easy.  After some very thorough bleeding they work the same and will barely slow the rear wheels down when I have it up on jack stands and have the truck in gear idling.  I can put a pressure gauge on to test but I know I'm low on pressure to the rear.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 22, 2020, 08:56:26 PM
Bought some more parts and went in the upgrade on the cheap direction but still no real progress.  I changed out the front calipers and pads and went to the 3/4 ton hd brake caliper and a quality pad and even though the truck already had aftermarket braided lines the new calipers required a different style banjo end so I got a new set of sky jackers braided hoses.  I also swapped out the master cylinder with a new one for a 2001 chevy Tahoe with vacuum booster application over the hydroboost.  I read many forums stating this was a good improvement over the stock 1984 setup.   I gravity bled everything and that went really well and I will follow up with some manual bleeding at some point but all in all the brakes are the same.  I'm thinking the last piece of the puzzle has to be the combination valve even though all testing showed it was fine. 

Should I simply install a new combination valve or remove it , and T the front lines along with adding an adjustable valve for the rear?
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: VileZambonie on May 23, 2020, 07:49:27 PM
Stock combination valves are fine. The more you deviate from the factory setup the more Frankenstein the truck becomes. The factory braking system will lock the rear brakes easily in a hard stop. You've definitely missed something!
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 23, 2020, 10:38:04 PM
Stock combination valves are fine. The more you deviate from the factory setup the more Frankenstein the truck becomes. The factory braking system will lock the rear brakes easily in a hard stop. You've definitely missed something!

Wish I could figure out what that is.  This truck has never had good brakes since the day I bought it and everything I try makes no change.  I'm down to the combination valve that passes all the tests I've been told to try and the last remaining item would be  the booster and that seems fine and passes the simple tests also.  I'm not a stranger to brake work and install complete new systems on a hand full of vintage vehicles yearly with great success with both aftermarket and oem parts so I'm scratching my head on this one.  About the only issue we ever run into is when the camshafts are borderline for vacuum brakes and we have to go a different route like hydro or electro boost systems.

I'm about ready to say thats as good as it gets and just drive it.
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: roundhouse on May 23, 2020, 11:08:54 PM
Bypass the combination valve and see what happens

You could also have a pinched line between there and the back axle

If you want to find out where the problem is
You need to get a gauge and start testing it at every junction starting at the wheel cylinders
Title: Re: My 84 K10 could use better brakes..What should be done?
Post by: 84Silverado4x4 on May 23, 2020, 11:24:11 PM
Bypass the combination valve and see what happens

You could also have a pinched line between there and the back axle

If you want to find out where the problem is
You need to get a gauge and start testing it at every junction starting at the wheel cylinders

I'll snag the gauge from work and check it out.  Can the rear lines on the frame be replaced and fished through easily enough if need be or do the bends and tight places make it nearly impossible?