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GI.SS

Drum to Disc Conversion

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We seem to be seeing the same questions for converting 2005+ drum rear brakes to disc brakes. What works what doesnt.... this write up is to inform others on what a guy on PT.net did.

 

pdxmatt on performancetrucks.net:

 

So my understanding goes like this:

 

99-04 trucks were 12" fronts and 12" rears with single piston calipers.

 

05-07c trucks they changed back to drums in the back and to 13" rotors and two piston calipers up front.

 

I'm not sure what year it started but I know that 05 and later SUVs (Tahoe/Suburban/Yukon) had 13" rears and larger two piston calipers.

 

My truck is an 05 Sierra. I am stock up front and I changed from drums to the 13" Tahoe rears. Everything is basically bolt on. Only major difference is that the SUV axles flanges are clocked on the 45, so they look like a diamond when viewed from the end. The trucks flanges are clocked so they look like a square. So you have to rotate the whole setup 45 degrees one way or another from the stock SUV setup, but the bolt pattern is exactly the same.

 

Here is the whole list of parts you need, this assumes you have drums brakes and need everything.

 

1. Disc brake backing plate. I used these from Napa http://www.napaonline.com/Catalog/Ca...RecType%3aA%29

 

They are the same part for both sides so you need two. These are not 100% necessary, its basically a dust shield, but it helps seal the parking brake. If you live in an area prone to rust there is a newer two piece design that lets you change them without pulling the axles. Almost everybody is making these now, including Dorman that you can get almost anywhere. Just search for "tahoe rear brake backing plate".

 

2. The actual mounting bracket. These are the same between the older trucks with 12" discs and the SUVs with either 12" or 13" discs. GM used these on almost everything. They are the same for both sides. The parking brake assembly mounts to this. I have the older original design ones that only have two contacts points for the parking brake shoe. There is a newer design that has three. Not sure if it's a big upgrade. The GM part number for the back plates that I used is 88983912.

 

http://www.ebay.com/itm/ws/eBayISAPI...vip=true&rt=nc

 

3. Parking brake parts kit. I think the parking brake hardware is the same between the 99-04 trucks and the new SUVS. The whole parking brake is made up of the shoe and then a small hardware kit with clips and what not. You can get it all separately but I ran into a problem. There is a small piece called the "hand brake lever" that none of the aftermarket kits come with. This is the actual lever arm that the parking brake cable attaches to and applies the force to the brake mechanism. Nobody includes this in the kit because its quite thick so it apparently doesn't wear out. Also, GM does not sell this part separately. It only comes in a kit that has two shoes and two parts kits. It runs about 100 bucks at the dealer. It has all the parts you need for the parking brake minus cables. I ordered this from the dealer for an 05 Tahoe.

 

4. Parking brake cables. Unfortunately the cables ends for drum and disc brakes are different. There are a ton of different cables out there, but I got lucky and got the right ones on the first try. I bought them from Rockauto and they were for an 04 silverado because they still had disc brakes then. Now, my truck is a crew cab and I assume yours is extended, being and SS. So I can't say for sure they will be correct for you. I will get the numbers at home tonight. These ran about 80 total for both.

 

5. Rotors. I used power slot rotors for an 05 Tahoe.

126.66045SL and 126.66045SR are the part numbers and I think the cheapest I found them was on Amazon. But you could use any rotors for an 05 Tahoe.

 

6. Calipers. The SUV calipers are not the same as truck calipers. They are larger two piston. Also I believe the 13" rotor is thicker. You will need calipers, pads and caliper mounting brackets. I found the easiest thing to do was just to order loaded calipers from Napa. I used LE5315 and LE5316. These are complete with calipers, pads, brackets and hardware. If you wanted to run different pads they also have semi-loaded calipers.

 

7. Brake lines. If your SF 14 bolt is like a 10 bolt then you have a single flex line going from the frame down to a Y fitting near the pumpkin and then hardlines from there straight to the drum cylinders. Obviously this isn't going to work for disc brakes. What I did was buy a 5 line braided stainless kit from Russel that was for an 04 Silverado. This includes the two front flex lines, and three rear flex lines. Now this part required some creativity or fab. The flex line from the frame to the rear axle is a direct replacement. but somehow you need to either modify or replace your two hardlines from the T fitting to each side of the axle. What I ended up doing was getting some cheap replacement hardlines from Napa. The lines were 3/16" tubing with 3/16" fittings and they are double flared. Napa carries these is a few generic sizes. I ended up using a 30" and a 40". These were a little too long so instead of doing some creative bending to use up some length I bought a double flaring tool from Napa and I cut them to the length I needed and reflared them. This is the only part of the job that wasn't really bolt on. I didn't even look into ordering factory hardlines from GM. In your case I think you'd be screwed on that since I don't think they ever did a SF14bolt with disc brakes. The Russel kit I used was http://www.summitracing.com/parts/RUS-672430/ (i believe the brake lines off of a 2500 with disc brakes should work. Or 03-04 SS would work as well)

 

8. Banjo bolts. You will need banjo bolts to connect the rear left and right brake hoses to the calipers. I just picked some up from Napa, I believe they are 3/8-24 thread.

 

Obviously alot of this could be done alot cheaper. I used all new parts and I didn't use the cheapest stuff available.

 

As long as your axle uses the same square mounting flange then all of this should bolt right up. The only vehicle this stuff doesn't work on is the hybrid Dana 60 they used on the quadsteer trucks, as far as I know. They had a rectangular mounting flange.

 

Good luck!

Edited by GI.SS

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