SubWarrior
Newbie
Trying to stop a fully loaded k1500 suburban in an emergency situation feels something like throwing out an anchor on the exxon valdez and praying for the best. In my opinion, the greatest flaw of the GMT400(OBS) half tons is the brakes. The most effective modification to remedy this starts with the brake boosting system. Hydroboost systems can provide almost double the pressure provided by vacuum boost. Many have seen 30-40 foot reduction in stopping distance from 60mph out of a hydroboost conversion, which is a tremendous improvement. My 2003 2500HD crewcab Duramax weighs in at ~4 tons and thanks to hydroboost (and much better rotors and calipers) , it will stop on a dime. My goal with this project was to upgrade the brakes on a 1999 k1500 suburban to roughly 70-80% of the GMT800 (NBS) duramax. Without 4 wheel discs, big rotors, and 2 piston calipers, I believe this is doable. In this thread ill share what knowledge i've gained about hydroboost conversions on these trucks, as well as the entire process of the conversion.
Disclaimer: ye be warned, this is a serious modification and should only be considered by seasoned mechanics. Even with all stock gmt400 parts you increase the complexity of your brake system and the margins for error are small. The information I provide here is for personal use and should not be regarded as professional. This modification is intended for off road use. Should it fail, whoever/whatever you destroy, as well as your insurance company, will know exactly who to blame.
What is hydroboost:
Simply put, it's a hydraulic contraption that uses the pressure from your power steering pump to amplify the pressure applied to the brakes when you step on the pedal. Its been around for decades and is seen most often on diesel pickups due to their inability to create vacuum. Its become increasingly popular on large gas vehicles, muscle cars, and hot rods as more effective braking system. Why don’t all cars have this system? Vacuum boost is less complicated, independent of power steering, and usually can provide plenty of boost on most vehicles with a well designed system. Hydroboost are more expensive, complex, and prone to leak. In addition, being run by power steering, when one goes they both go. yikes. For towing and off roading, these systems are almost a must and vastly increase the capabilities of your brake system in challenging situations. While the exact numbers vary between systems, you can expect roughly double the available braking pressure (at the calipers) over vacuum boost.
Many GMT400’s came stock with hydroboost. All the diesels, most of the 3/4t, and virtually all of the 1tons. I’ve never driven stock w/HB, but I hear the consensus is the stopping force is better and the pedal feel is an improvement. There are some good writeups out there on the conversion and parts needed. I hope to expand on the efforts of this great work and get some solid results on the use of an GMT800 system. The reason I chose to go the hard way is that the GMT800 hydro units are considered to be stronger and more reliable. Depending on where you buy your parts from, the cost of gmt800 components can be less and the rebuild parts easier to find down the road. The fabrication required to adapt gmt800 hydroboost to gmt400 is not overly complicated. There are some really good threads out there on this topic that were a big help, but I felt a detailed write up would be beneficial.
I would like to thank these members and threads for sharing their knowledge:
http://www.gmt400.com/forum/showthread.php?13105-GMT-400-Hydroboost-swap
http://www.gmt400.com/forum/showthread.php?11821-1500-Hydroboost-Conversion-Part-Numbers
http://www.performancetrucks.net/forums/gm-drivetrain-suspension-22/nbs-hydroboost-obs-491487/
http://www.gmc4x4.com/topic/2599-hydroboost-conversion/
What you need for the conversion
Money and time. Straight up, to do this project right it is not cheap nor will you pound it out in an afternoon. Budget $600 to $800 and 8-10hrs of work. You can take my word for it and those who have gone before me, It is well worth it.
Hydroboost unit
GMT400: ACDelco 178-578 $165
GMT800: ACDelco 14PB4054 $140 ( you will need a junkyard unit as well for push rod, retainer, return spring, and core charge)
Master cylinder : You have to match them up. So far as I know you cannot easily mix and match master cylinders & boosters.
GMT400: ACDelco 174-722 $97
GMT800: 18M2426 $70
Power Steering pump: Yes, buy the pump, there is a difference in pressure output. While many have retained the 1/2t pump and used a T for the extra return line, this falls short of how the Hydro Booster is designed to work. Don’t go through all this work for a sub par system. You have to take off the p/s pump to remove the EVOS anyways so mind as well put in the right one.
ACDelco 36-517137 $85
Duralast 7137 $54
Napa 385140 $62
Power steering cooler: Yes its necessary. The fluid gets very hot and if it foams thats a bad thing. Hotter fluids wear out expensive components faster.
GM p# 26041420 & 15655032 $100
Summit and others have coolers for cheaper, GM on bolts up quick and easy.
Variable EVO delete: Initially I thought it would be a Shame to lose it because steering becomes pretty light at highway speeds. This part is way more expensive than it should be. All you really need is the U shaped component when using a 3/4t pump. Thus far I have noticed lighter steering, but it has not been too much of a bother.
GM #19168825 $64
Power steering filter : often forgotten, but very necessary. Hydro Boosters are very sensitive to any particulate matter.
Magnefine $25
Wix $15
Brake pedal: Its down to junk yards only as of 8/12/2014 hardest part to find.
gm 5015868 $30
Lines
p/s pump to hydroboost ACDELCO Part # 36365460 $20
hydroboost high pressure to steering ACDelco Part # 36365490 $32
hydroboost return to pump ACDELCO Part # 36368640 $13
Steering return to pump - same as the one you have already.
Brake line adaptor: GMT800 mc only
AGS/1/2 in. - 20 inverted male to 9/16 in. - 18 inverted female port brass brake adapter (Autozone) $3
PN : BLF-26C
3/4t Calipers : Yes they bolt up and use the same pads
Right : FRC4414 $35
Left: FRC4413 $35
Stainless steel lines: I didn’t want to deal with a 15 year old rubber line bursting under the higher line pressures. Also makes a difference in pedal feel, stopping power and I have plans to lift in the future.
Skyjacker front pair $80
Skyjacker rear (Only need one) $40
Odds and ends
2 to 3 quarts ps fluid
about 2 quarts synthetic dot 3 brake fluid
I installed new brake pads, Hawk SD
Special Tools
Fan clutch removal tool (NAPA $21)
PS pump pulley removal tool (harbor freight $10)
Disclaimer: ye be warned, this is a serious modification and should only be considered by seasoned mechanics. Even with all stock gmt400 parts you increase the complexity of your brake system and the margins for error are small. The information I provide here is for personal use and should not be regarded as professional. This modification is intended for off road use. Should it fail, whoever/whatever you destroy, as well as your insurance company, will know exactly who to blame.
What is hydroboost:
Simply put, it's a hydraulic contraption that uses the pressure from your power steering pump to amplify the pressure applied to the brakes when you step on the pedal. Its been around for decades and is seen most often on diesel pickups due to their inability to create vacuum. Its become increasingly popular on large gas vehicles, muscle cars, and hot rods as more effective braking system. Why don’t all cars have this system? Vacuum boost is less complicated, independent of power steering, and usually can provide plenty of boost on most vehicles with a well designed system. Hydroboost are more expensive, complex, and prone to leak. In addition, being run by power steering, when one goes they both go. yikes. For towing and off roading, these systems are almost a must and vastly increase the capabilities of your brake system in challenging situations. While the exact numbers vary between systems, you can expect roughly double the available braking pressure (at the calipers) over vacuum boost.
Many GMT400’s came stock with hydroboost. All the diesels, most of the 3/4t, and virtually all of the 1tons. I’ve never driven stock w/HB, but I hear the consensus is the stopping force is better and the pedal feel is an improvement. There are some good writeups out there on the conversion and parts needed. I hope to expand on the efforts of this great work and get some solid results on the use of an GMT800 system. The reason I chose to go the hard way is that the GMT800 hydro units are considered to be stronger and more reliable. Depending on where you buy your parts from, the cost of gmt800 components can be less and the rebuild parts easier to find down the road. The fabrication required to adapt gmt800 hydroboost to gmt400 is not overly complicated. There are some really good threads out there on this topic that were a big help, but I felt a detailed write up would be beneficial.
I would like to thank these members and threads for sharing their knowledge:
http://www.gmt400.com/forum/showthread.php?13105-GMT-400-Hydroboost-swap
http://www.gmt400.com/forum/showthread.php?11821-1500-Hydroboost-Conversion-Part-Numbers
http://www.performancetrucks.net/forums/gm-drivetrain-suspension-22/nbs-hydroboost-obs-491487/
http://www.gmc4x4.com/topic/2599-hydroboost-conversion/
What you need for the conversion
Money and time. Straight up, to do this project right it is not cheap nor will you pound it out in an afternoon. Budget $600 to $800 and 8-10hrs of work. You can take my word for it and those who have gone before me, It is well worth it.
Hydroboost unit
GMT400: ACDelco 178-578 $165
GMT800: ACDelco 14PB4054 $140 ( you will need a junkyard unit as well for push rod, retainer, return spring, and core charge)
Master cylinder : You have to match them up. So far as I know you cannot easily mix and match master cylinders & boosters.
GMT400: ACDelco 174-722 $97
GMT800: 18M2426 $70
Power Steering pump: Yes, buy the pump, there is a difference in pressure output. While many have retained the 1/2t pump and used a T for the extra return line, this falls short of how the Hydro Booster is designed to work. Don’t go through all this work for a sub par system. You have to take off the p/s pump to remove the EVOS anyways so mind as well put in the right one.
ACDelco 36-517137 $85
Duralast 7137 $54
Napa 385140 $62
Power steering cooler: Yes its necessary. The fluid gets very hot and if it foams thats a bad thing. Hotter fluids wear out expensive components faster.
GM p# 26041420 & 15655032 $100
Summit and others have coolers for cheaper, GM on bolts up quick and easy.
Variable EVO delete: Initially I thought it would be a Shame to lose it because steering becomes pretty light at highway speeds. This part is way more expensive than it should be. All you really need is the U shaped component when using a 3/4t pump. Thus far I have noticed lighter steering, but it has not been too much of a bother.
GM #19168825 $64
Power steering filter : often forgotten, but very necessary. Hydro Boosters are very sensitive to any particulate matter.
Magnefine $25
Wix $15
Brake pedal: Its down to junk yards only as of 8/12/2014 hardest part to find.
gm 5015868 $30
Lines
p/s pump to hydroboost ACDELCO Part # 36365460 $20
hydroboost high pressure to steering ACDelco Part # 36365490 $32
hydroboost return to pump ACDELCO Part # 36368640 $13
Steering return to pump - same as the one you have already.
Brake line adaptor: GMT800 mc only
AGS/1/2 in. - 20 inverted male to 9/16 in. - 18 inverted female port brass brake adapter (Autozone) $3
PN : BLF-26C
3/4t Calipers : Yes they bolt up and use the same pads
Right : FRC4414 $35
Left: FRC4413 $35
Stainless steel lines: I didn’t want to deal with a 15 year old rubber line bursting under the higher line pressures. Also makes a difference in pedal feel, stopping power and I have plans to lift in the future.
Skyjacker front pair $80
Skyjacker rear (Only need one) $40
Odds and ends
2 to 3 quarts ps fluid
about 2 quarts synthetic dot 3 brake fluid
I installed new brake pads, Hawk SD
Special Tools
Fan clutch removal tool (NAPA $21)
PS pump pulley removal tool (harbor freight $10)
