Best brake mods.. Make your brakes actually work

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kylenautique

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Hi Everyone! This is my first post, but I have been wrenching on trucks since I was in my early teens. So, you have a GMT 400 truck, but the brakes are somewhat crummy... You have some options. This is what I did to make my 98 k1500 truck stop amazing.

First thing... Make sure all the little things are set up properly. Replace your pads with good pads. I use Powerstop z36 brake pads. Make sure your rear brakes are in good condition and adjusted properly. Its not a bad idea to adjust them every time you change your oil. Stainless Steel Brake lines make a difference! Replace the worn out stock rubber lines. These trucks are getting old, so its worth the money.

Second Step... The master cylinder. If you replace it, you MUST bench bleed it. Some of these trucks can be upgraded to the NBS master cylinder. Its very simple to do and requires one $6 adapter from autozone. Google the GMT400 NBS master cylinder upgrade. My truck however cannot use this. I have the JB6 brake code with the 14 bolt rear end. I was not able to get good pressure.. I think this mod only works with JB5 brake codes.

Third Step... The ABS unit. There is lot controversy on this. Trucks Prior to 95 have a rear only ABS unit. When they fail it can mimic a bad master cylinder. The simple way to resolve this is to remove it and just connect the lines together with a combination valve or adjustable proportion valve. 95 and up is a totally different beast. You have two parts to this system. The built in combination valve and the 4wheel ABS unit. You pretty much need a GM Tech2 scanner or Snapon scanner to bleed the system properly. If the ABS is failing, you can pull the fuse and it becomes a regular combination valve. In my case on my 98, the combination valve started sticking so my hydraulic brake side of the system was problem. No one really services these units and there are no parts available. The two options are, replace it with one from the junk yard, or delete it completely. I opted to delete it. Use this video for the fittings needed
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You simply T together the front lines and install a adjustable proportion valve for the Rears. You will be amazed at actually how awesome your truck stops. These trucks have amazing brakes, but I can almost guarantee if you did my Steps 1 and 2, if you still have issues, its going to be the ABS unit. They get gummed up from old Brake fluid. Remember these trucks are getting old, so some systems are going to fail. For me, I have driven many older vehicls without ABS, so I'm not a driver that needs it. If you are 17 years old and reading this, you may want to find a replacement ABS unit. All depends on drivers skill ABS is a good system, but I always find my self disabling it. If you rely on ABS and are not used to driving a truck without it, I don't recommend it

4th Step... You can install a hydrobost unit. Google this as well. To sum it up, 94 and older use a different pedal and hydroboost compared to 95 and up. Make sure you match this up, or you will be drilling your pedal. Hydroboost provides over twice the clamping force of a vacuum booster. For my 98, I don't feel I need this. Keep in mind hydroboost is amazing, but if your power steering pump fails or you get a leak while driving... you have 3 brake presses before you loose all braking ability.

So that's the trick everyone. These trucks can stop great. I have a 6" lift and 33" tires. I stop on a dime now. My next modification is to replace the rear drums with disc brakes.
 

rojas84

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I too have pulled fuses on my 2000 3/4 ton crew cab I have a hydrobooster/master cylinder from an 04 yukon that will be going in mine in the spring ,along with braided hoses and willwood proprtioning valve that has the adjustable valving for the rear after I remove the abs unit .. pic of said truck that I 5 lug swapped
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Schurkey

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Some of these trucks can be upgraded to the NBS master cylinder. Its very simple to do and requires one $6 adapter from autozone.
I have no idea what could be different about the "NBS" master cylinder compared to the stock one.

It's a cylinder. There's a couple of pistons, some seals and springs. The reservoir is a different shape.

If the old one works PROPERLY, I don't see how the newer design could be better assuming they're the same cylinder bore diameter.
 

delta_p

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I have no idea what could be different about the "NBS" master cylinder compared to the stock one.

It's a cylinder. There's a couple of pistons, some seals and springs. The reservoir is a different shape.

If the old one works PROPERLY, I don't see how the newer design could be better assuming they're the same cylinder bore diameter.

I've wondered about this too.

I was researching recently and that I can tell my '96 original MC has a bore dia. 1.574in. NBS MC up to '05 bore dia. 1.338in. NBS MC after '05 for rear drums bore dia. 1.125in.

My rear wheel cylinders are 1.18 in, and the NBS's up to '05 look to be 1.18 in. also. On the 05 up for rear drums there were two wheel cylinder sizes, .9375in for a reg. type cab, and a 1.0625in for ext. cab/crew cab.

Even though the pressure with NBS would be higher the MC travel should have to be more with smaller pistons. Since the volume of the caliper/wheel pistons are the same with an NBS MC change alone, it seems like the smaller MC would need to move more to maintain the volume with the smaller areas of the MC pistons in the NBS. I couldn't figure out why the pedal would feel tight. Unless it's really moving more but then feels tight because of the extra pressure? I wonder if a significant improvement wouldn't be noticed from replacing a wore out MC with a new one of the original OBS type.
 

Schurkey

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I was researching recently and that I can tell my '96 original MC has a bore dia. 1.574in. NBS MC up to '05 bore dia. 1.338in. NBS MC after '05 for rear drums bore dia. 1.125in.
"1.574 inches" would be 40 mm. 40 mm is the diameter of the quick-take-up part of the master, but it's not that diameter all the way through. The low-pressure section is 40 mm, the high pressure section would be 1 1/8.

They also had a QTU master that had a 36mm low pressure section, with a 1" main bore for high pressure.

This is the 40mm bore unit.
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Outlaw9890

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Hi Everyone! This is my first post, but I have been wrenching on trucks since I was in my early teens. So, you have a GMT 400 truck, but the brakes are somewhat crummy... You have some options. This is what I did to make my 98 k1500 truck stop amazing.

First thing... Make sure all the little things are set up properly. Replace your pads with good pads. I use Powerstop z36 brake pads. Make sure your rear brakes are in good condition and adjusted properly. Its not a bad idea to adjust them every time you change your oil. Stainless Steel Brake lines make a difference! Replace the worn out stock rubber lines. These trucks are getting old, so its worth the money.

Second Step... The master cylinder. If you replace it, you MUST bench bleed it. Some of these trucks can be upgraded to the NBS master cylinder. Its very simple to do and requires one $6 adapter from autozone. Google the GMT400 NBS master cylinder upgrade. My truck however cannot use this. I have the JB6 brake code with the 14 bolt rear end. I was not able to get good pressure.. I think this mod only works with JB5 brake codes.

Third Step... The ABS unit. There is lot controversy on this. Trucks Prior to 95 have a rear only ABS unit. When they fail it can mimic a bad master cylinder. The simple way to resolve this is to remove it and just connect the lines together with a combination valve or adjustable proportion valve. 95 and up is a totally different beast. You have two parts to this system. The built in combination valve and the 4wheel ABS unit. You pretty much need a GM Tech2 scanner or Snapon scanner to bleed the system properly. If the ABS is failing, you can pull the fuse and it becomes a regular combination valve. In my case on my 98, the combination valve started sticking so my hydraulic brake side of the system was problem. No one really services these units and there are no parts available. The two options are, replace it with one from the junk yard, or delete it completely. I opted to delete it. Use this video for the fittings needed
xc_hide_links_from_guests_guests_error_hide_media

You simply T together the front lines and install a adjustable proportion valve for the Rears. You will be amazed at actually how awesome your truck stops. These trucks have amazing brakes, but I can almost guarantee if you did my Steps 1 and 2, if you still have issues, its going to be the ABS unit. They get gummed up from old Brake fluid. Remember these trucks are getting old, so some systems are going to fail. For me, I have driven many older vehicls without ABS, so I'm not a driver that needs it. If you are 17 years old and reading this, you may want to find a replacement ABS unit. All depends on drivers skill ABS is a good system, but I always find my self disabling it. If you rely on ABS and are not used to driving a truck without it, I don't recommend it

4th Step... You can install a hydrobost unit. Google this as well. To sum it up, 94 and older use a different pedal and hydroboost compared to 95 and up. Make sure you match this up, or you will be drilling your pedal. Hydroboost provides over twice the clamping force of a vacuum booster. For my 98, I don't feel I need this. Keep in mind hydroboost is amazing, but if your power steering pump fails or you get a leak while driving... you have 3 brake presses before you loose all braking ability.

So that's the trick everyone. These trucks can stop great. I have a 6" lift and 33" tires. I stop on a dime now. My next modification is to replace the rear drums with disc brakes.
Do you have a diagram for where you have to drill the brake pedal for the hydroboost???
 

kylenautique

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Do you have a diagram for where you have to drill the brake pedal for the hydroboost???
I removed the stock pedal mount that attaches to the hydroboost rod, installed the pedal, moved it where I wanted it to sit, marked it, drilled it, reinstalled the hydroboost pedal mount in the new location, called it a day!
 
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