1963 GMC K10 stock BRAKE question-problem wont stop

[60-66]

1963 GMC K10 Brake question. All stock, no mods. I replaced every part except the metal lines. I don't or didn't see any reason to , was a very clean Montanna truck. This thing WILL NOT stop ! Rears will lock up if pressed very hard , fronts barely slow the truck down. All wheel cylinders brake hoses shoes are new, drums turned. I replaced it with three different, double, hydraulic clutch type master cylinders all NOS GM and one from a truck that works perfect , no change or difference. Pedal is at the top, no air in the lines and vacuum bled. I removed all the front metal lines after this, cleaned, ran a wire through them , cant find a restriction, rechecked wheel cylinders. The idea that the shoes needed to be arched to match the drum was also done. Still will not stop. All my other K10s stop fine and were easy. What am I missing ? Truck sat the last 10 years so the wheel cylinders froze , it all worked when parked but?

[blacknwhitedog]

Have you checked to see if the shoes are installed correctly on the front... its easy enough to put the long shoe on the wrong side, which would negate the self-energizing brake principle. I would re-check your brake shoe installation, making sure your primary and secondary shoes are installed correctly.

Also, have a buddy watch the shoes with the drum off, as you SLOWLY press the pedal to see if your wheel cylinders are working.

Worn backing plates with big grooves can cause this as well...not allowing the shoes to move as they should.



Should look like this....longer shoe towards the rear of the vehicle

[60-66]

Thank you for the response. I had to go check that again just to make sure. The long shoe was/is on the rear. I've been thinking of testing it like you said. Slow pressure to see if they,re moving , will do that when the wife gets home. Im curious now also if the shoe isn't hitting the radius or inner edge of the drum and not making full contact or being restricted. Will remove shoes and recheck backing plates. Thanks !

[blacknwhitedog]

It looks like your wheel cylinders also act as the upper pivot point for the brake shoes. I'm not a K-10 guy, but your front brakes look like non self energizing backing plates and shoes. Usually, there is a pivot point above the wheel cylinders that the shoes rotate (self energize) around, but in your pick it looks like the shoes go directly into the wheel cylinders. Has the rear axle been changed out? You may have self-energizing brakes in the rear, but not in front. That would explain the poor braking performance, with rears locking up.

I have a shop manual at home...I'll give it look to see if there's an exploded diagram of K-10 brakes.

[60-66]

I cant say for sure but theres no signs of anything being changed. Its a Dana 44 rear and all the parts I ordered were the same as the originals. This style brake setup was used 1960-1963 , 64-66 is different. These wheel cylinders have pucks that stick out past the boot and the shoes are longer at the top and contact the puck. Theres clips that hold the shoe to the backing plate and no adjuster on the bottom like most vehicles. The adjustment for the shoe is a cam and lock nut.

[blacknwhitedog]

OK....I think I found your problem. From the pics, these are not self energizing brakes. they are more like the old Lockheed version used early Fords. Your shoes are anchored to the backing plate at the bottom, just like an early Ford.

This from an older Ford site. Check the note on the location of the brake shoes, they are backwards from self energizing units...longer shoe goes on front. Shorter shoe on back. maybe this will help

LOCKHEED ‘39 THROUGH ’48 FORDS AND MERCS: These brakes were designed and
manufactured by Lockheed. Hydraulic pressure expands the wheel cylinder cups,
which push the shoes against the drum. The shoes are NOT self-energizing. The
Lockheed system is a front/rear shoe design with the bottom pivot for each shoe
anchored to the backing plate. This design requires more pedal pressure to stop
than self-energizing brakes since they rely solely on hydraulic pressure. The
front shoes (primary) do most of the stopping and normally use a longer friction
band. The rear shoes (secondary) normally use a shorter friction band.

[blacknwhitedog]

Meant to add...I'll check my service manual tonight to see if there is any reference on the K-10 brakes that confirm this.

[66Gilbert]

I think blacknwhitedog may be on to something? See the attached.

[60-66]

Originally Posted by blacknwhitedog

Meant to add...I'll check my service manual tonight to see if there is any reference on the K-10 brakes that confirm this.

Originally Posted by 66Gilbert

I think blacknwhitedog may be on to something? See the attached.

Fantastic work blacknwhitedog Thanks to both of you guys !!! Checked wheel cylinders, they are working fine , checked backing plate wear by polishing the pads a bit , they are fine. Will reverse shoes tomorrow and update. I hope this works !

[Classic v6 GMC's]

I would measure the distance of the pads and drum.

[jtrichard]

OK guys lets get out of the modern world these are Lockheed style brakes....... NOT Bendix ......Not self energizing ...... LONG shoe goes in front ... May have even had long on both front and rear originally ..... Best i found so far.... look here at posts 8 17 18 19 http://www.oldwillysforum.com/forum/...-install/page2

[blacknwhitedog]

60-66,

I checked the service manual last night, and yes, you do want the long shoe in front. Curious, are your rear brakes the same as your fronts, or are they more like a Bendix style of brake. Pivot point on top of wheel cylinder. If you still have a lock up problem on the rears after switching the front shoes, back off your adjustment on the rear slightly so they engage the drum a little later than the fronts.

[61K10]

It's in the manual as how the shoes go. jeep used this set-up for years. both shoes have to be adj. cam for each one. I put everything new in my 61 and a org power booster and they worked just ok. Back locked up on mine when in a real hard stop also.(backs are like regular adj brakes) i wasn't happy with the way it stopped. (not in today's speeds) put discs on my closed knuckle. I know you have a nice collection of k tks.

[60-66]

Originally Posted by jtrichard

OK guys lets get out of the modern world these are Lockheed style brakes....... NOT Bendix ......Not self energizing ...... LONG shoe goes in front ... May have even had long on both front and rear originally ..... Best i found so far.... look here at posts 8 17 18 19 http://www.oldwillysforum.com/forum/...-install/page2

Thanks jtrichard ! More great info , I learn something new in each reading. Did you also see the old Garage that guy restored ?

Originally Posted by blacknwhitedog

60-66,

I checked the service manual last night, and yes, you do want the long shoe in front. Curious, are your rear brakes the same as your fronts, or are they more like a Bendix style of brake. Pivot point on top of wheel cylinder. If you still have a lock up problem on the rears after switching the front shoes, back off your adjustment on the rear slightly so they engage the drum a little later than the fronts.

Rears are Bendix style. Hope to update later today. Thanks again, Jon

[jtrichard]

Yes great shop very nice

[60-66]

Well , moved shoes around, primary in the front , little to no difference. Im stumped.

[padresag]

it can only be so many things. mc giving the volume or pressure. w/c are they giving the push> you say you replaced everything; are they the correct ones. there is a restriction somewhere?
ron
did that 4 x 4 GMC rescue panel look inviting?

[aerotruk63]

Is the master cyl the right one? Two sizes were made. One for the Light Duty and another for the Medium/ Heavy duty.
When you go for a drive do all the drums heat up?
Wasn't there something about a pinched rubber line not allowing pressure to get through?

[jayoldschool]

The rear hose on my 65 failed internally while bleeding, giving me no brakes at all. Hard pedal.

[aerotruk63]

Link to album.
https://goo.gl/photos/mPShasG5whEnbB6T9

[60-66]

New wheel cylinders front and rear , fronts 1 1/8 bore rear 1 inch . Why if the fronts require more pressure aren't they 1" inch ? Parts book I believe confirms 1 1/8 size as correct.

I eliminated the possibility of restriction by running a wire through metal lines , cleaning and reinstalling front lines only, rears lock up but only when pressed hard. New hoses all the way around.

Drums are 11 inch size when new, left is now 11.040 and right is 11.030 after turning. I "lapped in" the new brake shoes by putting self adhesive sand paper in an 11.060 drum and turning drum by hand over new shoes. I have 3/4 contact so far on front shoe and 2/3 contact on rear shoe , this was only done to the front brakes. Shoes at first were wearing on the inner side only, and after lapping make contact all the way across but not complete dia.

Master cylinder I also looked up in the parts book , calls for 1 1/8 th bore,thats what I took off, tried three different masters, two NOS GMs and one off another truck that brakes work perfect on.

Im not ruling out that there still isn't a problem with the NEW USA made wheel cylinders but I've had them apart and checked operation and they do work, just not hard enough.

New hoses , I wouldn't "think" anyway, that they are the issue?

[60-66]

Originally Posted by aerotruk63

Link to album.
https://goo.gl/photos/mPShasG5whEnbB6T9

Thanks for posting that Aero , can you post the adjustment page please ? Its not covered in those two pages for K-1000.

[aerotruk63]

No separate power brake booster on the truck?

[60-66]

Originally Posted by padresag

did that 4 x 4 GMC rescue panel look inviting?

It did till I got detail pictures and talked to them. Front fenders were amateur patched, complete fresh paint job , I just feel after seeing the fenders they covered up other issues. I bought the same exact truck earlier this year with 6000 original miles and zero rust original paint.

[60-66]

Originally Posted by padresag

it can only be so many things. mc giving the volume or pressure. w/c are they giving the push> you say you replaced everything; are they the correct ones. there is a restriction somewhere?
ron
did that 4 x 4 GMC rescue panel look inviting?

Originally Posted by aerotruk63

No separate power brake booster on the truck?

Nothing