1981 Rear Disc Brake Parking Brake

[nas t eh]

This instruction sheet is pretty good

Just wanted to say thanks for this thread and this post.
I have a 79 disc rear end in my car and needed help to get it working.

[TATurbo]

YW. I'm happy someone found it useful!

[737driver]

A few months back I had to replace the rear calipers and discs on my 79 TransAm. Stock rear disc brakes. The is a good video on CPP Brakes website that talks about the Eldorado style disc brakes which are similar to the rwd on the TransAm.
https://youtu.be/SktF3ERaMC8?si=EDxxkQVlzqpeUZNh
If I recall , I also bleed the brake with the parking brake engaged.
The parking brake works exceptionally now. I did try it out from about 30 mph and it did stop the car reasonably well and as expected.
The video link help a lot but like I said I do believe the parking brake should be engaged when bleeding the brakes.
Jim

[737driver]

Here is another video that may be helpful


https://youtu.be/opjdu8DdVeA?si=qkkkLNtTSjfBcnr9

[81Blackbird]

Found this video.  He has a little different approach for the adjustment of the e-brake.
At time 3:08 he mentions that the piston rotates and pushes out.  That may have been an error since the piston and pad are locked together with a tang.  Later he mentioned the helix screw which is what
I think he meant.

[81Blackbird]

Called CPP for clarification on the setup.  The OEM parts are not self adjusting calipers.  They must first be set to a max of 1/8 inch play off the stop.  THEN as the pad wears
down the gap will slightly increase until the next tooth can be reached and the process starts over again.  Only when the pads are replaced will the setup have to be done from scratch.
The PN# for the 12-point lever is 4138/39-lever.  They are working on the site so it may not show up yet.  I found the e-bay site were they are selling these:


https://www.ebay.com/itm/265307820634


These levers look shorter.  If so, then the arc length will be shorter, which will give you less travel on the e-brake pedal to achive the same brake force.  You would therefore have more e-brake travel. May even hold on a hill or in neutral at 1500 rpm.
Would someone please confim that these levers look shorter?

[glhx]

I just did this adjustment again.

It’s a Lot easier with the special tool. So much so that I bought the tool for very little on amazon.

You cannot use a c clamp to push these back in. They need to be turned clockwise to go back in. That’s what the tool is for. I’ve taken them apart. It’s a very large screw. Which is why it only turns clockwise.

I did this with the caliper off the car. The first time. Using a rotor to adjust it. You can do caliper on car still connected but not bolted in. The rotor should be off the car. You really want that rotor sitting loos on the ground to do this.
In my opinion. Doing this with the rotor on the car isn’t feasible. At least not to me.

Once you have the tool and know what to do. It’s a pretty quick procedure. Minutes

I will add that the caliper is adjusted to almost barely touch the rotor at all times. That e brake doesn’t move the piston out much. We’re talking 1/16” or less of movement. The piston stays that close to the rotor at all times when this is adjusted right.

What I do. If any of this makes sense. Is put the piston lock……..almost to the top position. 12 o clock.
Almost…….
I have it 1/8” counter clockwise because I found that pumping the adjustment lever would move it too far when I had it aligned to the top. Since it’s a screw. It likes to turn the piston clockwise when it pushes the piston out when setting it.

I don’t get on here much lately so it would be best to email me and I’ll give my phone number to whoever is having problems. Glhxturbo@hotmail.com

https://www.amazon.com/gp/product/B01FW3U26G/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
This tool makes this whole thing……much much easier. I wouldn’t mess with this procedure without it.
That bigger disc in the corner sits right on top of your caliper piston. That little bump allows you to turn the whole piston with the other pieces.

The piston won’t turn counter clockwise. It will turn clockwise.
I pump it up 3 times to get the piston out.
Then turn it back in with the tool. Until it bottoms out
Until the odd piston lock hole lines up where I want. Usually at the 11:50 position on a clock.

The learning curve on doing this wasn’t easy but I’ve been successful with the procedure a few times.
I had to do it again when my axle seals failed and soaked the pads with 90 weight.

I also went to in-line tube and bought a new stainless steel kit. Fits perfect. Having new parts also made it easier.

[jbanna]

I'm sorry I didn't see your post earlier, but when I converted my 78 about 15 years ago, I used the housing and axles from an '81, and only had to buy a new proportioning valve and vacuum booster, as they are different; I also bought new rotors and calipers from NAPA, which are self-adjusting - you just have to use the parking brake often...I have had no problems in the 30k+ miles since whatsoever, and the braking improvement was tremendous!  ...I do seem to remember having to have longer studs installed on the rotors though...

[roadking77]

Ok.  This is stupid. I spent about 6 weeks fiddling with the stupid parking brake.  Spoiler Alert...It still aint right.
But all the parts are together and they should pass the PA State inspection.

Anyway, I figured I'd close the loop on this thread.

I finally found a picture of an actual marked, LH Caliper:

GM Left Rear caliper by Tom Sherer, on Flickr

I am having a hard time figureing out my rear brakes!! I have hard lines on the axle to the caliper, BUT in the pics shown it looks like instead of a banjo bolt there is some kind of banjo bolt with a square block with threads to accept the hard brake line? Is this a special part/fitting and where can I find one.

  As I suspected, the unmarked caliper on my left rear is wrong. You can see in the pic above how the park brake lever is up around 1 O'clock vs. 7 O'clock on the unmarked caliper I got when I ordered Ames PN FR218EB (now discontinued). 
Untitled by Tom Sherer, on Flickr

The orientation of the lever is determined by a metal 'stop' on the back side of the caliper + the hole that mounts the spring retainer.

Reviewing old GM Parts catalog info, combined with some notes I think came from a pre-crash TAC post from someone more familiar with these parts, I found the GM PN's for these calipers are:
18006748 Caliper Rear(LH)
18006749 Caliper Rear(RH)
And, These calipers were also used on Cadillac Seville's and El Dorado's of the era.

So, to have a properly installed and fully functional e-brake, I need to replace my LH caliper with the correct one.

Finally, I wanted to try to write something about adjusting the parking brake.  'Cause the instructions and video's I found seemed contradictory in some places.  Maybe its just how my brain works.  Here's how I'd describe the adjustment process:

Caliper is on the car.  Pads installed. 
When turning the post/actuator via the inner hex shape, the post will move in and out. There is some sort of ratcheting/clutch voodoo going on inside there.  While the post can push on the piston, it is not directly connected to it.

Because of the way the post moves in and out, you need to install the lever retaining nut onto the post while turning it with an open-end wrench.  The nut prevents the post from pulling too far in so you can't reach the inner hex shape...Like my first problem in this post.

Untitled by Tom Sherer, on Flickr

Turning the post clock-wise pushes the piston outward, clamping the pads to the rotor / actuating the brake.  Keep turning Clock-wise and eventually, the piston will clamp the pads on the rotor.  It'll get tight and wont turn Clockwise anymore.

Turning the post counter Clockwise backs the post off the piston. but, remember it's not connected.  So...it doesn't actually pull the piston back in.  Turning Counter clock-wise works the adjustment mechanism. Because of magical, self-adjusting clutch/ratchet in there, a person could spin and spin and spin Clockwise and not notice any change.  But, there's some sort of ratchet that is the key to adjusting the park brake actuator/lever. 

OK, so...With the nut installed on the post, put a wrench on the inner 9/16 Hex and turn clock-wise until it wont turn anymore. 
Here comes the 'trick'.  The lever needs to fit onto that inner hex shape in a position that leaves no more than 1/8" gap between the lever and the stop on the caliper.   Tighten down clock wise, then turn the post counter clock-wise.  Just a 1/4 turn or so.  You will feel the post try to pull in (but it can't 'cause you have the nut on there) you'll feel some resistance..push past it. That's the magical adjuster doing its job.  Now...turn back CLOCKWISE.  You should notice that your wrench doesn't return quite as far as where you started at before you feel it back to that tight position. 
Repeat this...Turn to tight...Turn 1/4 counter clock-wise...then back to tight. 
This ratcheting action moves the inner hex around. Repeat until is it clocked at the EXACT point where the lever will fit on with no more than 1/8" movement off the stop before it feels tight.

Good Luck!

-Tom

[roadking77]

Not sure why my writing did not show up, But I am having a hard time getting my rear calipers hooked up. I have hard lines on the axle and the connection to the caliper is with a banjo bolt. The hard lines DO NOT connect directly to the caliper. In the top pic above you can see the new banjo bolt. In the second pic with the red caliper you can see a 'block' screwed in where the banjo bolt is that accepts the hard line. What is this special fitting called and where can I get a couple?