Mechanics

SEE PHOTO: ARE THE REAR DRUM BRAKE SPRINGS IN THE CORRECT POSITIONS?

1985 Toyota Pickup • 75,000 miles

This is from a 1985 Toyota Motorhome. My rear brake shoes went down to metal after less than 5000 miles. I am wonderning if they were put on incorrectly. I am doing this myself. In the picture I included you can see the lower spring is touching the self adjuster wheel. This doesn't seem right. Can you please send me a diagram or picture of a correctly done job? With the springs and parts in the right place? The Haynes and Chilton only show for half-ton and these are a 1 ton full floating axle which replaced the original axle on this motorhome. These axles were sent by Toyota to National RV who made this motorhome. Thanks


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PCMentor29
May 7, 2013.



This is a common Chrysler brake and I see two things that are noteworthy. First of all, you're right about that lower spring. It is supposed to be in the largest hole on the right side; one hole higher. Chrysler is famous for making parts that interchange and / or have multiple uses. In this case that hole the spring is in now would be used to pound in the pin for the adjuster lever when new linings are bonded on and that frame is used for a rear shoe.

This should be the right rear brake. The lining on the right which should be the front of the vehicle should be the shorter lining, and the left one, what's left of it, should be longer.

The second thing is the parking brake lever hanging down behind and from the left shoe. That lever is supposed to be all the way back. That lever is held forward like it is in your photo when the cable gets rusted tight in the applied position. There's two things to verify that is what caused the linings to wear so quickly. First look at where the two shoes contact the large anchor pin on top. If either one is being held away from that pin the front shoe will grab too easily and commonly cause easy rear wheel lockup under light braking.

The next thing to look at is the parking brake strut bar running right under the wheel cylinder. With your thumb you should be able to push that bar forward a good 1/8" against the pressure of the anti-rattle spring on the right. You'll find your bar is tight between the two shoes because the parking brake lever is being held forward. That lever should be pried rearward to create the 1/8" play in the strut bar.

It's a little hard to see for sure but it looks like the front shoe is being held away from that top anchor pin. Also, look at that Chevy bow tie-looking metal bar on the anchor between the two shoes and the two return springs. It looks like the hole is not centered on the anchor and it's too far away from the shoes. That needs to be lifted up so it snaps closer to the shoes. That will let the return springs seat fully and it will prevent the shoes from moving 1/8" away from the backing plate and chattering when they don't hit the drum squarely.


Caradiodoc
May 7, 2013.
Thanks for your expert reply. I am going to work on it in a couple days. I will post what I find. I printed out your reply and will check each thing you suggested. You are right, it's the passenger side rear wheel in the picture. Thanks


Tiny
PCMentor29
May 8, 2013.
Hi, I am waiting for the new brake drums to get here. I had more questions though about the springs. Please see the attached photo. Can you tell me what the small, long spring is that anchors to the backing plate and the rear shoe? Should it be in another place? What is it for? Thanks


Tiny
PCMentor29
May 8, 2013.
Here's a closeup crop of the two spring hooks.


Tiny
PCMentor29
May 8, 2013.
What I have learned is this is a duoservo type brake and has a backup adjuster vs the parking brake activated. Am I right here? From the Toyota EPC diagram(Village Toyo site) that extra spring seems to be just an extra secondary shoe tightener attached to the backing plate. It may work with the movement to allow the adjuster to function. Can you input on this? Thanks


Tiny
PCMentor29
May 8, 2013.
Sorry for taking so long. Went to a friend's body shop to help with two smashed vehicles. He specializes in rebuilding one and two-year-old Chrysler products.

That spring of which you speak is not standard Chrysler issue and I don't have an answer. That tab is spot welded to the backing plate which suggests it was a Toyota modification with a specific purpose, but my only guess is it was to prevent a moan or chatter. It's going to pull both shoes forward. Logic would say that is going to make the front shoe rub on the drum, but I'm sure the engineers had something in mind.

I'll keep looking for a better answer.


Caradiodoc
May 8, 2013.
Yup, it's a duo servo brake. The front piston pushes the top of the front shoe into the drum which rotates and pushes the bottom of the rear shoe into the drum through the adjuster. The rear piston pushes the top of the rear shoe into the drum. Those two forces acting on the rear shoe makes it a duo servo brake. That's also why the rear lining is longer. It does the stopping.

The shoes do adjust when backing up. Very few designs use the parking brake to adjust drum brakes. When backing up the two shoes switch jobs. The rear shoe gets pushed out on top and the cable guide pulls on the adjuster cable to raise the lever. I can't see any way for that extra spring to affect the adjuster mechanism.


Caradiodoc
May 8, 2013.
I have looked through my 6 general autoshop texts, 3-4 brake manuals, and an old(90-96) Chilton general truck manual. I have searched hundreds of images on Google, I have the Factory manual(paper and online, also the 1993 edition which should have the 1 ton axle brake in but doesn't) for this truck and 2 haynes and one Chilton specific for this truck. I searched through Autoshop 101 site too. No where have I seen the spot welded spring holder and spring we are wondering is used for. I will put it where it is when I do the job unless I get the needed info. Thanks for your help.


Tiny
PCMentor29
May 9, 2013.
Caradiodoc, I have the brakes off and am trying to see if there's a problem with the Emergency brake sticking. I measured the cable that goes into the drum brake housing. When emergency brake handle fully pulled up the cable/spring measures 70 mm. Fully let out it measures 94 mm. Which is about 1 inch travel. Is this enough travel? Or should I adjust the splitter under the truck? I was worried the shoes wore out because the emergency brake was not releasing. Could it have been caused by something else? Do wheel cylinders stick when they go bad? Thanks for your help.


Tiny
PCMentor29
May 17, 2013.
I never measured how far the cables move so I can't tell you what's normal. There's normally two things to look at. First of all those two levers hanging down behind the rear shoes must go all the way back into the shoes. The tops of the shoes must rest against the top anchor pin and there must be free play in the strut bar between the shoes. Apply and release the parking brake, then verify those three things to tell if they both fully released.

Next, with the drums on, the parking brake should get tight when you move the pedal or lever no more than half way. That will allow for some cable stretch to take place.

If those two things are correct the cables are not sticking and they're fully releasing.


Caradiodoc
May 17, 2013.
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