I have a '99 2-door 4WD Tahoe, and what I'm looking for is a bolt-on front brake upgrade using factory parts. I have the JB5 system like most 1/2 tons do. The brakes are...not great in their current form with 150k miles, and I'm unsure of how the previous owners maintained the system so I'm replacing everything that's easy/cheap.
My plan is to, at a minimum, replace the front calipers, rotors, pads, drums, shoes, and upgrade to stainless lines. The caliper swap is mostly due to necessity - driver side is an aftermarket part of questionable quality as the broken-off bleeder screw can attest to. I'm also willing and ready to swap out the master cylinder and vacuum booster - I know praises have been sung about Hydroboost but I'm just not committed to that extra work at the moment (again looking for a bolt-in solution if possible).
I know that the 3/4 calipers with a larger piston are bolt-in on the 1/2 4WD spindles. I know that due to the larger bore, I can expect some change in pedal feel. These are also the same calipers used on the Police units. However, I noticed that the Police units have a specific master cylinder, as it is my understanding they came from the factory with the JB7 front/JB6 rear( 3/4 ton calipers, MC with smaller bore, and 11" rear drums). RockAuto confirms different MC part numbers:
ACDELCO 18M1492 {#18030956, 18M714, 19176102} Professional (JB5/JB6 specs)
without Police Package
ACDELCO 18M712 {#18030954, 19176104} Professional (JB7 specs)
w/ Police Package
It seems that doing the JB6/JB7 rear conversion would require either an entirely new rear end or modification of the backing plates, neither of which I'd consider "bolt-on".
I'm sure you've seen this comparison of JB5-JB6-JB7 before:
JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder
JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"
JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder
So here's my question. Can I use a JB7 master cylinder/calipers on my 2 door 'hoe while retaining the factory 10" JB5 rear system? Or would the MC pressure be off considering the rear is smaller than it was designed for? If it's feasible, is it even worth it? Have I been swimming in this alphabet soup of brake designators too long? Should I just do the caliper upgrade and replace everything else with 1/2 ton parts? Any guidance would be appreciated!
My plan is to, at a minimum, replace the front calipers, rotors, pads, drums, shoes, and upgrade to stainless lines. The caliper swap is mostly due to necessity - driver side is an aftermarket part of questionable quality as the broken-off bleeder screw can attest to. I'm also willing and ready to swap out the master cylinder and vacuum booster - I know praises have been sung about Hydroboost but I'm just not committed to that extra work at the moment (again looking for a bolt-in solution if possible).
I know that the 3/4 calipers with a larger piston are bolt-in on the 1/2 4WD spindles. I know that due to the larger bore, I can expect some change in pedal feel. These are also the same calipers used on the Police units. However, I noticed that the Police units have a specific master cylinder, as it is my understanding they came from the factory with the JB7 front/JB6 rear( 3/4 ton calipers, MC with smaller bore, and 11" rear drums). RockAuto confirms different MC part numbers:
ACDELCO 18M1492 {#18030956, 18M714, 19176102} Professional (JB5/JB6 specs)
without Police Package
ACDELCO 18M712 {#18030954, 19176104} Professional (JB7 specs)
w/ Police Package
It seems that doing the JB6/JB7 rear conversion would require either an entirely new rear end or modification of the backing plates, neither of which I'd consider "bolt-on".
I'm sure you've seen this comparison of JB5-JB6-JB7 before:
JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder
JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"
JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder
So here's my question. Can I use a JB7 master cylinder/calipers on my 2 door 'hoe while retaining the factory 10" JB5 rear system? Or would the MC pressure be off considering the rear is smaller than it was designed for? If it's feasible, is it even worth it? Have I been swimming in this alphabet soup of brake designators too long? Should I just do the caliper upgrade and replace everything else with 1/2 ton parts? Any guidance would be appreciated!
