Author Topic: My 84 K10 could use better brakes..What should be done?  (Read 3086 times)

Offline MIKE S

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #15 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. 

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #16 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.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #17 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?
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline MIKE S

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #18 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.

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Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #20 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.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline MIKE S

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #21 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.
« Last Edit: April 15, 2020, 03:45:20 PM by MIKE S »

Online bd

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #22 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?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #23 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. 
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Online bd

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #24 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?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline MIKE S

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #25 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.

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #26 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?
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #27 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.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline ehjorten

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #28 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.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline JohnnyPopper

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #29 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.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction