Finally did this swap, just coulden't stand the sight of the huge drums behind the wheels.

It was well documented, many thanks to these guys:
http://www.andyz28.com/3rdGen/1leupdate.html
https://www.thirdgen.org/forums/faq-...iscs-89-a.html
http://www.ws6transam.org/1LEbrake.html
https://www.thirdgen.org/forums/brak...drum-rear.html
https://www.thirdgen.org/ls1reardisc
http://home.comcast.net/~afgun/cars/1LE_retrofit.html

Important factor was to use O.E. parts, otherwise it would not be street legal, or insane amounts of money would need to be spent to have everything tested and approved.

Once the drums and accessories removed, I decided to grind away around 2 mm off the axle flange to be sure the O.E. disc will fit over it.





Traced a line with a marker as reference, to help take off an equal amount all around it.

 

A clean axle flange and loctite to glue the axle spacer ring in place.
Got the "Rear Axle Spacers (pair)" from andyZ28 http://www.andyz28.com/catalog.htm



The Latex glow is practical to keep the dirt out of the axle



Pressed in new wheel studs, a little longer then the stock ones, for the case I would need that little bit longer, sometime in the future.
Part# Dorman 610-323 (M12/1.5 x 54 mm)

 

Backing plate shimms are used to center the caliper bracket over the disc, requires to install the axle and caliper bracket a couple times.

Wery little grinding is required to the drum axle flange, to clear the shim.

Shim is also used as template to drill the holes for the disc backing plate bolts.
"Shim Kit (2 ea. .032" shim templates & 2 ea. .060" shims)" from andyZ28 http://www.andyz28.com/catalog.htm





Not sure why the bolt on the E-brake bracket needs to be that long.

 

I could not find any O.E. disc backing plates, so I ended up with new replacements from Ebmiller http://www.flynbye.com/catalog/i29.html

I left the rear axle flange as is for now, for the case I stumble across an uncool inspector.





The e-brake cable seems too long, at least thats what I thought at first, though after installing, then hanging them up correctly and pulling the e-brake once, they fit perfect.
O.E. part# from Dorman is C94264 (for 89-92 models)

 

Instalation of the Rear axle lines for disc brakes is easy and they are available from http://www.finelinesinc.com/catalog/...oducts_id=1153

Luckily, reproductions of the O.E. "Brake Line Brackets (set)" are still available from http://www.andyz28.com/catalog.htm
The mounting holes are already drilled in the drum axle.



Here are two pics of the L and R PBR calipers, these are from early 4th gens but are basically identical to 3th gens PBR calipers.
Notice the different design at the back were the banjo bolt holds the rubber brake line in place, I hat to buy 3 R calipers to get one that would match the L side one :go crazy:



PBR rear caliper hardware were also in all different colors, so I ended up with a matching set from Ebmiller http://www.flynbye.com/catalog/i233.html

 

Drove around with the disc drum combination valve for a little while because Bruce from Hawksthirdgenparts, sent me a dirty and clogged 1LE valve, but I recived and installed the clean replacement that I have ben told comes from Ebmiller.
I am courious to test the difference.



Replacing the combination valve/ proportioning valve, requires to empty the whole master cylinder and reservoir.

The 89-92 O.E. rear disc specs:

Outer working diameter 11.65 in
Inner working diameter 8.31 in
Thickness 0.79 in
Matl & type, Cast iron Vented

The disc brakes sure do look much better behind the wheels



I upgraded the front with 1LE brakes already a couple years ago, got the complete kit from Ebmiller http://www.flynbye.com/catalog/i55.html, still working great.



Front 1LE O.E. specs:

Outer working diameter 11.86 in
Inner working diameter 7.77 in
Thickness 1.03 in
Matl & type, Cast iron Vented

 

What exactly does that big bolt on the emergency brake bracket do anyway?

 

If its what Im thinking of, it holds a steel and rubber dampener. they started putting them on in late 91 or early 92.
edit: just looked at the pix and yup thats what its for.

 

JamesC

 

Ah, I see. I wondered as mine don't have those.

I'm curious as to why people bother with the shims, which require pulling the axles out a couple of times, when you can just sandwich washers in between the backing plate and carrier to get the same effect and not remove the axles multiple times.

 

I can only speak for myself, but I used shims because that's the way GM assembled and because shims simply seem tidier in application than washers.

Here's a pic of the dampener, should anyone be interested:

http://www.ls1tech.com/forums/conver...-calipers.html

JamesC

 

Ok, thanks, I knew about the damper, but none of the 3 91-92 J65 equipped camaro/firebirds, I worked on the brakes, had the dampers.
Probably going to replace that long bolt with a short one someday, if no noise awakens.

I really prefer the shims behind the backing plates, with this swap the axles have to come out. Installing the correct shims, results in 30 minutes more of happy wrenching, well worth a nice job

 

I've never seen the dampeners on those years either. I always thought they were part of the fourthgen change. Here's what Ed Miller says about them:

"There's a slight difference in 3rd and 4th gen calipers and you got a 4th gen caliper. They aren't finned all the way (LS1s mainly), the e-brake bracket is stronger to account for the steel dampener, hence the extra plate, and that big bolt thing is for holding the big steel vibration dampener that the '93-97 LT1 calipers come with. No big deal really as they will work the same, it's just that they look different. The 4th gen parts are becoming easier to find so that's what you got."

That said, IIRC, TTOP350 once mentioned that the dampener was original to his 92.

JamesC

 

Did you use a shorter bolt, or just leave as is?

Another thing I was wondering about, are the e-brake cable guides on the differential cover from your wery helpful tread https://www.thirdgen.org/forums/post...606-post5.html
I do not remember seeing them on 3rd gens either, were they part of the O.E. ?

 

There was no bolt on mine. If you're not intending on using a dampener, I'd simply remove it.

IIRC, those were fourthgen guides.

JamesC

 

Build date of 09/91 and it has the factory dampeners

 

Thanks, TTOP.

Be interesting to know when the introduction date of the dampener truly was.

JamesC

 

Okay, got it. 4th gen and 3rd gen e-brake brackets are different.
3rd gen https://www.thirdgen.org/forums/atta...s-89-lline.jpg
3rd gen https://www.thirdgen.org/forums/atta...s-89-rline.jpg
The bolt also appears to have a structural function, on the 4th gen bracket.



Thank you alot for the good pic, it shows clear how the dampener is bolted on the rear and higher up vs the 4th gen dampener bolt.

 

Little road test report, the difference in braking is wery noticeable between the 1LE prop. valve and the J41/J42 (disc + drum) prop. valve.
Diden't do any crazy braking yet, but overal it feels like it brakes more.

 

@thomas1976. Did you notice if the 1LE rear or front brakes pushed your wheels out any farther? I have drums in the rear too.

 

The fronts are approximately 1/4" wider per side. Never noted any difference in the rears.

JamesC

 

The fronts came out around 7 mm (0.2756 in), the rears do not change*.

The drum is 4 mm (0.1575 in) thick, were it contacts the axle flange, and comes with a 3 mm extra spacer.

The rear disc is 7 mm thick, were it contacts the axle flange.

*If you add the (drum) spacer to the disc, it sticks out 3 mm (0.1181 in) more.

In this circumstance, the wheel doesen't center it self anymore and requires to evenly hand tighten the Lug nuts for precise alignment, before final torque.

The stock studs also appear a little short for discs with that extra spacer, I used Part# Dorman 610-323 (M12/1.5 x 54 mm), for this and the following reason.

The total of the front (outside wheel to outside wheel) with 1LE brackes, mesures around 14 mm (0.5512 in) larger then the total of the stock rear (outside wheel to outside wheel).

I wanted to be able to even out this difference, by adding a 7 mm spacer on each rear side.