Installing NBS Truck Rear Disc Brakes on your OBS Truck/SUV...
In this writeup I am going to show you how to adapt the rear disc brakes from a 99-06 GM pickup or SUV (NBS) onto your 88-99 (OBS) truck or SUV. In this case, we will be installing these on to my 95 Chevy Tahoe 4X4.
Also, doing this swap onto a 10 bolt requires spacers if you have a 4wd.. I wound up having the need for a 20mm spacer. Then everything just bolts right up! (Thank you Generous Motors) but if you have a 14 bolt, it can be done just as easy, except you will be needing two 60MM spacers, and it will then bolt right up too!
10 bolt 4wd = 20mm spacers
14 bolt 4wd = 60mm spacers
I am aware there are many fine kits out there for adding rear disc brakes, but in the state in which I live, a parking brake is required for inspections, and a line lock will not be acceptable as one. Those kits would require a caliper from a older Cadillac, and those were less than reliable.
The first thing you will need are the parts. You can buy it all new (expensive) or go to the Men's Mall (junkyard). Here is a list of what all you need.
The e-brake cables to make the e-brake work when using the NBS rear discs came from a 2001 Regular Cab Short Box (RCSB) 1500 truck. Basically, just unhook the OBS rear cables at the connector (see diagram) and then connect the intermediate cable to the OBS front cable. then route the two rear cables from the NBS, use a bracket for the cable sleeves, and connect it all.
Grab all the rear brake parts, and the e-brake cables. if you want dual piston calipers, look for a tahoe, yukon, or suburban, as those had the dual pistons. One thing to know - you need to get the clipers and caliper brackets from the same truck. Reason - they changed the rear brakes in 06 as well as the fronts, and they went to a beefier rotor and different pad design. Those parts will work with the e-brake setup from an earlier truck, they bolt right on - but the caliper brackets are different, which is why I did my swap with parts from a 03. Also, the e-brake cables on the SUV's have different cable ends than the trucks do, so if you get backing plates/e-brake assemblies from a 'burb or a 'hoe, get the brake cables from it as well. The intermediate cable from the chevy truck I mentioned is universal, so you can just get it from the parts store.
Here's some of my newly aquired parts...
As you can see, they clearly came from the junkyard! but a little cleaning and they will be fine! I will have to pick up new backing plates, because as is the norm here up north, they rotted away...
So get the calipers, caliper brackets, backing plate/e-brake assembly, hoses, and rear e-brake cables from the truck, and then go find an intermediate cable from a 99-01 chevy RCSB truck. Bolt it all together, and BOOM. Rear discs. I got everything I needed for $40 bucks!
Let's do this!
The first step of course is to remove the rear diff cover and pull the axles. You will need to also then pull the lock pin out of the carrier by removing the 8mm retaining bolt as seen below..
Then, using a tool like I found here, remove the C-clips and then the axles.
Use the old drums to hold your axles up off the floor that way keeping the studs from getting messed up.
This is all the junk we are replacing...see ya!
Remove the 4 bolts surrounding the axle tube and remove the backing plate.
Before we continue, I must advise... 14 bolt rear ends require a 60mm spacer, on the 4x4 10 bolt tahoe I needed a 20mm spacer. Guess what I didnt have? Yep...a 20mm spacer.
I decided after talking to a few people that I can use washers as spacers, so thats what I did. But not just any washer. They have to be small enough to fit. I used the following...
I also picked up these bolts to be sure I had some sticking out of the axle flange. I wanted grade 8 bolts, but was unable to locate them locally in this size. The hardware man thought these will be fine since there are 4 of them on each one. I plan to have spacers made and then I will have the grade 8 (or higher) bolts when they are changed out.
I needed to grind a flat spot on 8 wshers because of a lip around the axle flange. I wanted everything to be just right.
I used a little superglue to hold these in place. Line it up, glue it on, insert a bolt to make sure you are lined up, let it sit a few minutes, then take the bolts back out. This washer counts as 1 of 8. You will install 7 more. The total of washers I used was 32 per side, or 8 per bolt.
Here's my stack. This is 8 including the grinded one. (greasy ones)
New backing plates, bolts with the 8 washers installed on the flange. Don't forget lock washers on the bolt head. I used a impact gun to install the bolts, but don't get carried away cranking on it.
Re-install the axles, c-clips, retaining pin and lock bolt, and this is what you should have at this point. It took me 4 attempts to get the measurements right, and they are perfect with the 8 washer stack.
Bolt on the caliper bracket and insert the pads.
The drivers side is on.... I clocked this one at 10 o clock, facing the front.
Passenger side is the same, 10 o clock looking at it, however it faces the rear of the truck. I chose these for ease of hooking up my brake lines, and for the later running of the e-brake cables. You will need to bleed from the banjo bolt on the hose top, as the bleeder screw is on the bottom.
Now the fun...
While I had the lines all apart, I decided that there was no better time than now to install the newer 02 master cylinder. The reason I chose to do this is I read it has a firmer pedal feel and is a easy install. Plus, it is already desinged for disc/disc brakes, unlike the old disc/drum one.
Bye, old friend!
In with the new! Oh, the front line, you will need to get a adapter, AGS #BLF 26C, available at Autozone. Make sure you bench bleed the master first, then it will be good to go!
All on... At first she groaned a little, which lasted long enough for everything to get seated where it needs... I am VERY pleased with the results. Before this swap, the brake pedal would go 3/4 of the way to the floor before whe would begin stopping. I unplugged the ABS, which helped the feel a little bit. After this swap, the pedal is just pushed less than 1/4 down, and she is stopping! I plugged in the ABS fuse again, and working great!
Now, also, having run this setup for a few weeks now, I am going to be making one more change. I neglected to change out the porportioning valve from the original disc/drum to a disc/disc one. This will be easily solved by pulling one from either a S-series blazer with rear disc, or off a newer truck. I am leaning to the S-series as the fittings should be the same.
Another thing...Don't do what I did...I was so busy test fitting the stuff on the passenger side that I neglected to make sure the bolts that held the caliper bracket to the mounting bracket were totally tight. I found out about that 2 weeks after the install when one came out and the truck came to a screeching halt when I hit the brakes. No damage done. New bolts, blue locktite, and crank em in. Fixed! Embarrassing, but fixed...
I have read where guys have swapped out the bigger 3500 series OBS front calipers and got a much better pedal feel with the old drums on the rear. This doesn't work apparently with the change to the rear disc and NBS master cylinder. In fact, adding the bigger front calipers actually brings back the mushy pedal feel, so I have read. I am going to leave the fronts alone for now.
E-Brake cables coming in soon, needed to order them in new...stay tuned!