Build up part 3 Rear Disc brakes

[Bill usn-1]

Well the project creep is getting to me but here is part 3.
I'll start with the parts I have selected so far.

The rotors.
Standard brake PN 81-61809
For a 1991 GMC K1500 4wd truck front rotor.
Price $27
These are 6 lug rotors.
Well get to that later.

The alternative was the 79 ford F150 front rotor. PN 141214
It's a 5 on 5.5 pattern but the center hole was very large and the rotor was ticker. I felt it may be a problem with the calipers. Others have said they have used them?

Other build ups.
Rear Disc Jeep D300 OBA OBW Interior PS pump reseal Hydro-boost Mirrors Headliner
SOA Bushing replacement Roll cage And of course..FI

[Bill usn-1]

Rear flex lines so you can remove the caliper without disconnecting the line.
1985 Cadillac eldorado or Oldmobile Toronado rear.
Hose. BH98915 price $8.99

[Bill usn-1]

Calipers.
1985 cadillac eldorado or oldmobile toronado rear.

A1 Cardone PN 18-4138 and 18-4139
Price $60.99 ea.

[Bill usn-1]

As I stated the rotors I choose were 6 lug so they require drilling them to a 5 on 5.5 pattern.
At first I was really concerned but it turned out to be pretty easy and straight forward.

I used the drum as the pattern.
If you set the rotor on top of the drum you will see that 1 of the holes lines right up.
The center hole has a raised flange that keeps the rotor centered. So I just used an old wheel stud and lug nut to lock the 2 in place.

[Bill usn-1]

With the 2 locked together I stuck a 1/2" bit in my HF drill press and drilled the remaining 4 holes.
Once they were at 1/2" I pulled out my .600" bit and drilled them again. (my .600 is not good enough to do it alone)

When done I unbolted them and cleaned up the holes.
Notice how nice the center hole fits!!

[Bill usn-1]

Here is a caliper loaded and test fit on the rotor.

[Bill usn-1]

one more.

[Bill usn-1]

OK day 2.
I gutted the diff since I had to do the gear swap and posi install.
Here is the end of the tube with everything removed.

[Bill usn-1]

Next I trial fit the brakes on the axle to see where it all shook out.
Here it is setting in place.
I used a zip tie on the parking brake lever to hold it in place and centered.

[Bill usn-1]

First thing I found was where the bracket needs to set, the axle tube flanged out. If I left it like that I would loose about 1/4-3/8" of brake pad contact with the rotor.

So I had to mark how much I needed to go and ground it out with the angle grinder. Then I layed the second one on top of the first and marked it.

EDIT: I'll move this info from the back of the thread to the front.

I used the 3 in but I had to grind it out to fit the raised part on the axle flange. PN 40121

If you are looking to use the large GM calipers then here are the brackets for them.
Caliper Bracket Rear - GM - 3 1/2in. Radius
PN 40120-1
Part: 40120-1 Price: $11.99


AFCO

[Bill usn-1]

Here is the bracket now tacked in place.
Note the gap between the retaining plate and the diff flange.
The original backing plate is .125" or 1/8". So when you remove it you need to take up the difference.
I could not bring myself to cutting up the backing plates so I grabbed a couple of .060 washers for each bolt and out them in.

Speaking of the retaining bolts.....
You need to make sure you have the bolts in and thru the flange before welding the bracket on.:eek:

[Bill usn-1]

Here is the bracket all welded in.

[Bill usn-1]

Once the brackets are welded on, then it's just putting everything together, plumbing the lines and making a spacer for the brake cable.

[Bill usn-1]

And here is the install.
I used steel line to connect to the flex line.
I used 3/16 X 6".

After getting it all plumbed I think I would have changed my installation a little.

I set the calipers straight back. After looking at the lines I think I would have gone a little hight just to give a little more protection on the lines from rocks.

[CIAScoutman]

Sweet set Bill

[Eagle-Mark]

If you set them higher would the bleeder be in the correct location?

BYW cool thread as always.

By the dates on your pictures you've been working on this for years! :confused:

[Bill usn-1]

Update coming.
I woke up this morning not liking the position so I cut them all off and rewelding them at 75*. The bleeder is fine.
I am also completing the parking brake.


I lost the batteries in the camera!

[Bill usn-1]

Ok with the brackets rewelded on at 75*, I feel better about my hoses and the parking brake cable has more droop.

Speaking of which.
This is how I fixed it.

First I removed about 1-1.5 inches of the spring from around the cable.

[Bill usn-1]

Here is the springs now.

[Bill usn-1]

Then to take up the slack in the cable I removed the mounts from the frame and rewelded them further back. This basically makes the end of the cable shorter so it will work.
Here is the stock location.

[Bill usn-1]

And here is how far I moved it back.
Laying on my back!!

[Bill usn-1]

So if anyone is actually thinking about this, there is still one obticle to overcome!

The rotor thickness makes the studs too short!

So...since I am also running alum wheels I need some more studs.

Dorman to the recue.
I am using the 290 for the rear and the 277 for the front.
One note...the front studs will stick out past a steel wheel so you can not use them if you have thin steel wheels without a spacer.

The rears are in and done but I have to pull the front back apart to replace them!

Here are a couple of pics.

[Bill usn-1]

Pic two.

[Bill usn-1]

and do you want to know how close the brakes are to the wheel?

[Bill usn-1]

One final note.
After I started using the E-brake, the cable started to stretch back out so now I don't have a lot of adjustment left in the cable.
I even loosened the adjustment before welding the brackets back on..
And the E-brake is kind of weak.
It works but that's about all I can say about it.

Ok so it's done Now I have to take it around the block.
It all works with the scout on stands and running in gear but now to check out my 3.73's and the new brakes!