Trans Am disc axles

[Bonnewagon]

The levers, brackets and springs don't come with the rebuilt calipers. I would imagine they are hard to find separately.

What about the calipers? Do they use right and left or two rights/lefts because of the non-staggered shocks. I ask because I see kits that say "two rights" for (fill in the blank) models. Those would be otherwise the same? F-body rotors can be had brand new easy enough.

 

[Texas82GP]

What about the calipers? Do they use right and left or two rights/lefts because of the non-staggered shocks. I ask because I see kits that say "two rights" for (fill in the blank) models. Those would be otherwise the same? F-body rotors can be had brand new easy enough.

The calipers are left and right, due to the e-brake cables pulling the levers on both sides to the front. I think the casting is the same but the worm screw for the piston is the difference to accommodate the different direction the lever needs to swing from left to right. I believe the E-brake cable brackets at the caliper and the levers are left and right as well. I found a few pics from my brother's build thread....

The real trick with this system is adjusting the calipers once they are mounted on the axle with the rotor and pads. You have to turn the piston to take up the slack between it, the pads and the rotor and then install the lever arm and let it rotate back to the stop. Otherwise, you have little to no emergency brake, no matter how much you tighten the adjuster and you basically have no back brakes. We have the Pontiac factory service manual but the write up on the procedure for adjusting these was difficult for me to understand. I ended up buying another reman caliper to work with on the bench. When you are turning that piston or worm screw (that the lever fastens to) it wants to pull down into the casting so you have to put the nut on the stud and turn the worm screw with a wrench on the boss that the lever mounts to. That way the wrench is sandwiched between the casting and the nut, the way the lever would be. This might not make sense. If you get to a point you are doing this, PM me and I'll talk you through it. We used all the parts for the Pontiac with the WS6 rear brakes including the booster, master cylinder and proportioning valve. Also, the pedal is different. The point where the push rod mounts to the pedal, in relation to the pivot point is different between the drum brake and rear disc cars.

My brother loves the feel of the rear disc system. I don't really care for it. I prefer rear drums. I like a high, firm pedal from drums that are adjusted pretty tight. The rear discs stop great. They just don't feel how I want them to. My brother's truck is rear disc so he's used to it. It's just a different animal.

 

[Texas82GP]

One more pic I found that might or might not be helpful.....

 

[Bonnewagon]

I meant the calipers on the other models, not the F-bodies, which we know have staggered shocks and require left/right units. When I got my first disc rear it was intact. So all I did was R&R into my '77 TA. No problems with the parking brake and it held really good. Some have reported the parking brake being useless as an emergency brake but I think they just had not figured out how to get it adjusted right. I knew right away that 4 wheel discs are the ONLY way to go for stopping power. Why do drum brakes even exist anymore? I also used the 4 disc MS and combo-valve. I wanted no issues. I did not know about the different brake pedal. Compared to the drum rear, where is the push-rod hole? Higher or lower?

 

[Texas82GP]

Compared to the drum rear, where is the push-rod hole? Higher or lower?

That will take some digging. It's been too long. I don't remember. Let me do some looking.

I'll agree to disagree on "why do drum brakes even exist."

 

[Texas82GP]

Found it quicker than I thought. Scroll down a bit to see the measurements....

4 wheel disc cars have different brake pedal pushrod pin position?

Hi guys, I read on an ebay auction for a "4 wheel disc" brake pedal for a 2nd gen that the booster pushrod pin location is different on a disc/drum pedal than it is on a 4 wheel disc pedal. Has anyone ever verified this? Is this one of those, it will work either way but the 4 wheel disc pushrod...

nastyz28.com

 

[Bonnewagon]

Thanks for that Jared. So the 4WD had the hole .4" lower on the pedal shaft. That would give a smidge more leverage. I won't sweat looking for one. I also have the dual diaphragm booster but I used the disc/drum pedals. At least I think I did. The pedal cluster was a swap meet item so it may have even been the right one. I never felt the 4WD brakes were anything but terrific. As for drums, try doing the rears on a Cobalt.
They use a gigantic single spring that is impossible to do without the special tool. I figured out a work-around but much cursing as involved.

 

[Texas82GP]

Thanks for that Jared. So the 4WD had the hole .4" lower on the pedal shaft. That would give a smidge more leverage. I won't sweat looking for one. I also have the dual diaphragm booster but I used the disc/drum pedals. At least I think I did. The pedal cluster was a swap meet item so it may have even been the right one. I never felt the 4WD brakes were anything but terrific. As for drums, try doing the rears on a Cobalt.
They use a gigantic single spring that is impossible to do without the special tool. I figured out a work-around but much cursing as involved.

You're welcome. I hope the information is helpful. My brother's car was an automatic so our brake and clutch pedals were reproductions and the brake pedal was for a rear drum car. We just modified that pedal. We didn't do so initially, as we were unaware of the difference and I think the pedal was even incorrectly listed for either rear disc or drum. We modified the pedal because we were unhappy with the performance of the system, and came to understand the pedals were different when looking for a remedy. The real problem at that time was that the rear calipers and emergency brake were not correctly adjusted. We had to learn how to work on that system. Now that it is right, it stops very well.

I hear you on that moronic "W" spring on the modern drum brake systems. My 2008 Sierra has that. I did a rear brake job that it didn't need back in 2012 and I had a hell of a time with that thing. Next time, I'll have the tool. I just don't get the high firm pedal feel that I like out of rear discs. I'm also of the opinion that if you aren't going to autocross and build up that kind of heat, rear discs are really unneeded. Just my opinion, and you know what those are like. 😉

 

[Bonnewagon]

I just don't get the high firm pedal feel that I like out of rear discs.

Funny you should say that. The very first set of front disc brakes I had on my '68 Firebird- was from a guy that "hated the low pedal" that he got from the disc brakes. He wanted to swap for a set of front drums- so I did. I never looked back. Then we figured out how to make a '79 TA rear fit in a '68 and once I felt 4WD I was hooked.

 

[Texas82GP]

Funny you should say that. The very first set of front disc brakes I had on my '68 Firebird- was from a guy that "hated the low pedal" that he got from the disc brakes. He wanted to swap for a set of front drums- so I did. I never looked back. Then we figured out how to make a '79 TA rear fit in a '68 and once I felt 4WD I was hooked.

I'm a stodgy guy. Why else would a 45 year old own a 96 Roadmaster?