Brake Upgrade Question

[bob_o]

I have a '75 GMC 1/2t that came with non-power brakes. The master cylinder is on its way out so I figure now is a good time to upgrade to power assist.

Here's my question: Can I just buy a booster/master setup for a same year truck and install it without any modification?

If I will need to modify or change anything, what will I have to do?

Thanks in advance!

Bob

[MSL]

It has been a while but when i changed from non assited to assist i took the brake pedal out of a truck with assist since i do believe that the shaft is different.I could be wrong so if anyone could chime in that would be great.

[walkerb]

Originally Posted by MSL

It has been a while but when i changed from non assited to assist i took the brake pedal out of a truck with assist since i do believe that the shaft is different.I could be wrong so if anyone could chime in that would be great.

You are correct. You will need a power brake pedal assembly.

[bob_o]

Cool, thanks for the info!

[C10wip]

How soon are you going to do this? I did the power brake conversion three weeks ago on my 80 C-10 1/2T. There's a lot of info out there but there were also a few small details that I had to find out the hard way so I was planning on posting those fairly soon.

[cool68]

C10wip I will wait for added info that you can add to this conversion. I have a '76 with front disc brakes and no power assist, like stopping with drum brakes.

[moregrip]

looking forward to your detail as I am upgrading to power as well

[C10wip]

OK, I'll put it together in the next 3-4 days.

[C10wip]

OK, here's 95% of what I have. I don’t claim that all of this is original, it’s a combination of what I found in various places and what I had to do. I have gotten tons of useful info from the group here so I’m trying pay back a little here. I don’t have the brake boot info yet but I promised something today so here it is. I figured I would put something here to get you going.
My truck is a 1980 C-10, disc front/drum rear, 4.1L engine. I’m guessing/assuming that the brake system is all OEM. For the SPI / Service Part Identification, the manual brakes are code JB1 and the single diaphragm vacuum booster power brakes are JB3, same disk/drim size for both. JB5 is the dual diaphragm vacuum booster with the same front disks and slightly larger rear drums. I went from JB1 to JB3.
My master cylinder had a ton of sludge in it so I wanted to put in a new master cylinder at the same time as the booster.
So – there’s a lot of info below, but I don’t want to make it look more complicated than it is, I just want to point out a few things to consider beforehand. Overall this is a pretty straightforward, fairly low cost and well worth the effort. If I hadn’t had to mess with the fittings, it would have been smooth. So, you may want to read through all of this, see what might apply to you and make your shopping list.

Brake lines and fittings: Check this first! For me, this turned what should have been a pretty quick install into a bit of a pain, mostly because I wasn’t expecting it. I suggest that before you tear into this project, verify that the brake line fittings on master cylinder will break loose without twisting the brake line ( may want to spray with PB Blaster first ). If they do, then life is good. However, mine were really rusty and the fitting would turn but the line would not despite many forms of persuasion, and I ended up cutting the lines near the cylinder. If this is the case for you also, there are a few options:
a. Use the old lines. Buy new tubing nuts, get a hold of a double flare flaring tool set and have at it. I got the loaner tool flaring kit from AutoZone as well as some tubing to practice on. The nuts and tubes are different sizes, one is ½-20 with 3/16” tubing ( AGS Part BLF-41C-5) and the other is 9/16-18 with ¼” tubing ( AGS BLF-43C-5). The parts places will have tons of 1 to 7 foot straight lengths pre-flared with fittings – but likely none with these tubing sizes and nut combinations. If you go the flaring route, there are tons of good videos on YouTube. What I got out of the videos was – practice first and a lot, lubricate, keep it straight, make sure the inside of the flare is round, and use a good flaring tool set. This approach is a bit of a hassle as it means you will have to make the flares with the tubing on the vehicle and without the benefit of a vise, but it can be done.
b. Same as above except buy new tubing as well. You can buy copper-nickel tubing which is corrosion resistant and easier to bend. The auto parts places sell this in 25 foot reels. Lots of people do this and swear by it. You can also do the rest of your truck later.
c. Buy a pre-formed set; there are a number of outfits like Inline who sell them for $100/set or so for the 4 front lines, and you can get them in stainless. I am planning to do this later, and if I had more time, I would have done this from the start.
d. Go to an industrial hydraulic line place like AeroQuip and have them flare and bend something for you. No idea what this would cost but if you needed it right away and are not confident flaring tubing, this could work.

Vacuum booster/master cylinder: I bought a Cardone model 50-1108. This is a master cylinder/vacuum booster combo. It comes with a two piece threaded pedal rod ( which has a ½” hole for the pedal pin ) and lock nut, and the booster check valve, but does not have the boot for the booster. Some people have gotten the whole unit from a junkyard but I wanted new stuff, and the new units are only $90 - $100. The advantage at the junkyard would be that it would be cheaper, and you could probably also get the vacuum hose, boot, and fittings.
The booster has some sort of corrosion resistant coating. The M/C does not, so you may want to paint or coat it before installation if you don’t want it rusting right way.

Power Brake filter. The booster unit comes with a check valve but not a filter. These are generic, cheap ( $7 ) and easy to get, I used the Help!/Dorman part #80195. This is also useful as it creates a 90 degree elbow. I tried to run the hose so that it would not be too stressed and kink later on, and the 90 degrees reduces some of that.

Vacuum Hose: You will need to get some power brake vacuum line hose. Supposedly it’s special because it takes vacuum rather than pressure and needs to be sturdy since the consequences of it collapsing are serious. There was some debate on whether or not regular 3/8 vacuum or fuel hose was good enough but I didn’t want to take chances and it really isn’t that expensive, although it is not easy to find. Autozone, O-Reilly and Advance didn’t have any, even online, so I bought mine at Carquest as part number 27230 which is 11/32” ID, $2.08/ft. The specification is SAE 1403/L. The fittings are 3/8” but fit the 11/32 hose well. I bought 3 feet but had at least a foot left over.

Vacuum port: I have a manual transmission, so to get a vacuum port I just had to remove a plug with a square drive on it ( looks like your basic 3/8 NPT plumbing plug ) from the base of the carb on the driver’s side. For a port, I used a brass 3/8 NPT air line fitting with a hose barb from NAPA, and these are easy to find. From what I have read, if you have an automatic this port may already be taken and you will have to tee into a line.

Vacuum hose routing – I bought an extra 90 degree 3/8 vacuum fitting in case I needed to route the hose differently, I didn’t use it but depending on you configuration you might need to. I figured I could always take it back.

Check valve positioning. The check valve comes with the booster on the one I bought. The shop manual, page 5-38 says “Be sure the vacuum check valve on the power brake unit is positioned from the vertical as shown in figures 5-48 and 5-49”. For the 4.1 and 7.4, that’s pointing to the passenger side, at a 9 o’clock position looking from the front towards the firewall. The 4.8 is at 6 o’clock and the 5.0, 5.7 and 6.6 are at an 8 o’clock position.

Brake Pedal – I re-used the same pedal based on the info in thread number 511709 in this forum
http://67-72chevytrucks.com/vboard/s...=Manual+brakes
which was helpful. It has a picture comparing two pedals. The advantage of getting a junkyard unit would be that it probably already has the correct pin and brake light switch plate on it. However, I used the pedal and plate I had. A couple notes on what’s in that thread though – I removed the upper clevis pin, thinking that I would just stick it in the middle hole. However… the pin is 5/8” diameter and the middle hole is ½” diameter. So, buy a 1/2 “ clevis pin from Lowes or Tractor Supply with a matching hitch pin, and cut it in half. Also be aware that the ½ “ hole in the pedal will need to be opened up a bit as it is undersized. I drilled it out to ½” and then tacked in on the back with my trusty wire feed welder; I did this with a ½” bit on a drill press rather than a dremel as I wanted the pin to stay tight and in line. Drilling the hole out to 5/8” to reuse the pin was not an option since the Cardone pedal rod hole is ½” diameter to match the expected ½” pin. And I could not re-use the old rod either since it mounted into the M/C and could not be mounted to the Cardone M/C.
I don’t know if you could just leave the old pin in or not, might be worth checking to save some work. You will also need to modify the brake light stop plate; the bottom bolt hole is still good but you will need to drill a hole to allow the new pin to go through and will also need to hammer flat the top part that lays against the pedal arm. The part which touches the brake light switch stays the same. When you’re done you should adjust the brake light right away or the brake lights will stay on and kill the battery if you don’t notice that they are stuck on. A picture of the pedal and new pin is below.

“Reversing” the brake lines: I have seen some threads where people ask if they have to reverse the brake lines. You can’t really reverse them since the nuts are different sizes. However, it seems that the master cylinder itself is reversed between the manual version and the power version, that is, the small reservoir is on the front of the M/C in the manual setup, but is on the rear for the power version. What this means is that you need to cross the brake lines, which may be where the “reversing” question comes from. So, my lines look like spaghetti now and this is another good reason to buy some pre-formed lines. System still works properly under normal operation and lockup.

Boots: The big piece of info I’m missing here is the correct boots. The Cardone part comes with a tag that says “Reuse the old boot”. The problem is that if you’re upgrading as we are, you don’t have an old boot. So, I called Cardone and they do not sell boots, but the Cardone factory guy was very helpful and is going to look for a decent old one and send it to me.
But - if anyone has the original part number and possibly a picture of how they mount up, please let me know. I bought the Bendix boot from GMCPaul’s but it looks too big. I also bought the firewall boot which looks like a cone, part number 8699126. Those are more readily available.

Useful Tools:
Tubing Bender: I have a couple of Harbor Freight tools which were useful. I know they’re sort of disposable tools, but these two worked fine. The Tubing Bender was HF # 94571 which is good because it can bend to 180 degrees.
Metric offset wrench set: HF # 32042.
Master Cylinder Bleed Kit: This is a Dorman kit for $10 part # 13911., and is several fittings, a few pieces of hose and two clips to hold the hoses inside the master cylinder. You only need about ¼ of what’s in the kits since it’s meant to cover all sizes. I used the two fittings I needed and the whole master cylinder bleeding went quickly and cleanly with no drama. Could you rig up something like this yourself? Probably, if you have the nuts, two short pieces of 3/16 and ¼ tubing with flares and some hose. If not, this kit is good.
Brake bleeding kit: I have a MityVac kit which is good and recommended. However, I may try one of the Motive Products Power Bleeder kits - not too expensive and this is even better. You can get them with Chev master cylinder adapters.

Have fun, it's worth the effort, night and day difference. I hope this helps.

[C10wip]

And this was another good thread I saw here, off a '69 but similar.
http://67-72chevytrucks.com/vboard/s...d.php?t=221598

[moregrip]

Originally Posted by C10wip

OK, here's 95% of what I have. I don’t claim that all of this is original, it’s a combination of what I found in various places and what I had to do. I have gotten tons of useful info from the group here so I’m trying pay back a little here. I don’t have the brake boot info yet but I promised something today so here it is. I figured I would put something here to get you going.
My truck is a 1980 C-10, disc front/drum rear, 4.1L engine. I’m guessing/assuming that the brake system is all OEM. For the SPI / Service Part Identification, the manual brakes are code JB1 and the single diaphragm vacuum booster power brakes are JB3, same disk/drim size for both. JB5 is the dual diaphragm vacuum booster with the same front disks and slightly larger rear drums. I went from JB1 to JB3.
My master cylinder had a ton of sludge in it so I wanted to put in a new master cylinder at the same time as the booster.
So – there’s a lot of info below, but I don’t want to make it look more complicated than it is, I just want to point out a few things to consider beforehand. Overall this is a pretty straightforward, fairly low cost and well worth the effort. If I hadn’t had to mess with the fittings, it would have been smooth. So, you may want to read through all of this, see what might apply to you and make your shopping list.

Brake lines and fittings: Check this first! For me, this turned what should have been a pretty quick install into a bit of a pain, mostly because I wasn’t expecting it. I suggest that before you tear into this project, verify that the brake line fittings on master cylinder will break loose without twisting the brake line ( may want to spray with PB Blaster first ). If they do, then life is good. However, mine were really rusty and the fitting would turn but the line would not despite many forms of persuasion, and I ended up cutting the lines near the cylinder. If this is the case for you also, there are a few options:
a. Use the old lines. Buy new tubing nuts, get a hold of a double flare flaring tool set and have at it. I got the loaner tool flaring kit from AutoZone as well as some tubing to practice on. The nuts and tubes are different sizes, one is ½-20 with 3/16” tubing ( AGS Part BLF-41C-5) and the other is 9/16-18 with ¼” tubing ( AGS BLF-43C-5). The parts places will have tons of 1 to 7 foot straight lengths pre-flared with fittings – but likely none with these tubing sizes and nut combinations. If you go the flaring route, there are tons of good videos on YouTube. What I got out of the videos was – practice first and a lot, lubricate, keep it straight, make sure the inside of the flare is round, and use a good flaring tool set. This approach is a bit of a hassle as it means you will have to make the flares with the tubing on the vehicle and without the benefit of a vise, but it can be done.
b. Same as above except buy new tubing as well. You can buy copper-nickel tubing which is corrosion resistant and easier to bend. The auto parts places sell this in 25 foot reels. Lots of people do this and swear by it. You can also do the rest of your truck later.
c. Buy a pre-formed set; there are a number of outfits like Inline who sell them for $100/set or so for the 4 front lines, and you can get them in stainless. I am planning to do this later, and if I had more time, I would have done this from the start.
d. Go to an industrial hydraulic line place like AeroQuip and have them flare and bend something for you. No idea what this would cost but if you needed it right away and are not confident flaring tubing, this could work.

Vacuum booster/master cylinder: I bought a Cardone model 50-1108. This is a master cylinder/vacuum booster combo. It comes with a two piece threaded pedal rod ( which has a ½” hole for the pedal pin ) and lock nut, and the booster check valve, but does not have the boot for the booster. Some people have gotten the whole unit from a junkyard but I wanted new stuff, and the new units are only $90 - $100. The advantage at the junkyard would be that it would be cheaper, and you could probably also get the vacuum hose, boot, and fittings.
The booster has some sort of corrosion resistant coating. The M/C does not, so you may want to paint or coat it before installation if you don’t want it rusting right way.

Power Brake filter. The booster unit comes with a check valve but not a filter. These are generic, cheap ( $7 ) and easy to get, I used the Help!/Dorman part #80195. This is also useful as it creates a 90 degree elbow. I tried to run the hose so that it would not be too stressed and kink later on, and the 90 degrees reduces some of that.

Vacuum Hose: You will need to get some power brake vacuum line hose. Supposedly it’s special because it takes vacuum rather than pressure and needs to be sturdy since the consequences of it collapsing are serious. There was some debate on whether or not regular 3/8 vacuum or fuel hose was good enough but I didn’t want to take chances and it really isn’t that expensive, although it is not easy to find. Autozone, O-Reilly and Advance didn’t have any, even online, so I bought mine at Carquest as part number 27230 which is 11/32” ID, $2.08/ft. The specification is SAE 1403/L. The fittings are 3/8” but fit the 11/32 hose well. I bought 3 feet but had at least a foot left over.

Vacuum port: I have a manual transmission, so to get a vacuum port I just had to remove a plug with a square drive on it ( looks like your basic 3/8 NPT plumbing plug ) from the base of the carb on the driver’s side. For a port, I used a brass 3/8 NPT air line fitting with a hose barb from NAPA, and these are easy to find. From what I have read, if you have an automatic this port may already be taken and you will have to tee into a line.

Vacuum hose routing – I bought an extra 90 degree 3/8 vacuum fitting in case I needed to route the hose differently, I didn’t use it but depending on you configuration you might need to. I figured I could always take it back.

Check valve positioning. The check valve comes with the booster on the one I bought. The shop manual, page 5-38 says “Be sure the vacuum check valve on the power brake unit is positioned from the vertical as shown in figures 5-48 and 5-49”. For the 4.1 and 7.4, that’s pointing to the passenger side, at a 9 o’clock position looking from the front towards the firewall. The 4.8 is at 6 o’clock and the 5.0, 5.7 and 6.6 are at an 8 o’clock position.

Brake Pedal – I re-used the same pedal based on the info in thread number 511709 in this forum
http://67-72chevytrucks.com/vboard/s...=Manual+brakes
which was helpful. It has a picture comparing two pedals. The advantage of getting a junkyard unit would be that it probably already has the correct pin and brake light switch plate on it. However, I used the pedal and plate I had. A couple notes on what’s in that thread though – I removed the upper clevis pin, thinking that I would just stick it in the middle hole. However… the pin is 5/8” diameter and the middle hole is ½” diameter. So, buy a 1/2 “ clevis pin from Lowes or Tractor Supply with a matching hitch pin, and cut it in half. Also be aware that the ½ “ hole in the pedal will need to be opened up a bit as it is undersized. I drilled it out to ½” and then tacked in on the back with my trusty wire feed welder; I did this with a ½” bit on a drill press rather than a dremel as I wanted the pin to stay tight and in line. Drilling the hole out to 5/8” to reuse the pin was not an option since the Cardone pedal rod hole is ½” diameter to match the expected ½” pin. And I could not re-use the old rod either since it mounted into the M/C and could not be mounted to the Cardone M/C.
I don’t know if you could just leave the old pin in or not, might be worth checking to save some work. You will also need to modify the brake light stop plate; the bottom bolt hole is still good but you will need to drill a hole to allow the new pin to go through and will also need to hammer flat the top part that lays against the pedal arm. The part which touches the brake light switch stays the same. When you’re done you should adjust the brake light right away or the brake lights will stay on and kill the battery if you don’t notice that they are stuck on. A picture of the pedal and new pin is below.

“Reversing” the brake lines: I have seen some threads where people ask if they have to reverse the brake lines. You can’t really reverse them since the nuts are different sizes. However, it seems that the master cylinder itself is reversed between the manual version and the power version, that is, the small reservoir is on the front of the M/C in the manual setup, but is on the rear for the power version. What this means is that you need to cross the brake lines, which may be where the “reversing” question comes from. So, my lines look like spaghetti now and this is another good reason to buy some pre-formed lines. System still works properly under normal operation and lockup.

Boots: The big piece of info I’m missing here is the correct boots. The Cardone part comes with a tag that says “Reuse the old boot”. The problem is that if you’re upgrading as we are, you don’t have an old boot. So, I called Cardone and they do not sell boots, but the Cardone factory guy was very helpful and is going to look for a decent old one and send it to me.
But - if anyone has the original part number and possibly a picture of how they mount up, please let me know. I bought the Bendix boot from GMCPaul’s but it looks too big. I also bought the firewall boot which looks like a cone, part number 8699126. Those are more readily available.

Useful Tools:
Tubing Bender: I have a couple of Harbor Freight tools which were useful. I know they’re sort of disposable tools, but these two worked fine. The Tubing Bender was HF # 94571 which is good because it can bend to 180 degrees.
Metric offset wrench set: HF # 32042.
Master Cylinder Bleed Kit: This is a Dorman kit for $10 part # 13911., and is several fittings, a few pieces of hose and two clips to hold the hoses inside the master cylinder. You only need about ¼ of what’s in the kits since it’s meant to cover all sizes. I used the two fittings I needed and the whole master cylinder bleeding went quickly and cleanly with no drama. Could you rig up something like this yourself? Probably, if you have the nuts, two short pieces of 3/16 and ¼ tubing with flares and some hose. If not, this kit is good.
Brake bleeding kit: I have a MityVac kit which is good and recommended. However, I may try one of the Motive Products Power Bleeder kits - not too expensive and this is even better. You can get them with Chev master cylinder adapters.

Have fun, it's worth the effort, night and day difference. I hope this helps.

Awesome info! thank you. Interested in some pics if able......and what boot you end up using

[cool68]

Great info - Thanks. pics would help a lot

[walkerb]

Nice write up.

[C10wip]

Thanks! Minor correction - I said that the problem was that the brake line fitting would turn but the line would not - wrong - the problem was that they both turned because they were rusted together and the line was twisting.

This weekend I'll post some pics of the filter/vacuum port/check valve position, the backwards m/c's, one of the boots and the bleeder tool.
btw Cardone is now sending me a boot in the mail, so we'll see what that looks like.

[C10wip]

Here are a few pictures with labels. The M/C painting was probably a waste of effort, I was just ticked to see it rusting instantly. I would suggest painting beforehand if you really want to paint. I am replacing the lines later so I didn't care about the overspray.

[C10wip]

Also an annotated version of the first picture

[C10wip]

Updates on the upgrade info:

I installed the used booster boot I got from Cardone ( http://67-72chevytrucks.com/vboard/s...d.php?t=618235 ) and it fit properly. The large end is not a tight fit but the firewall end fits perfectly. Still, I have no idea what the part number is; Cardone just got it from a core unit they received and it is not a Cardone part. Would be nice to have the number since you'll need it for the upgrade; the Bendix and firewall boots I bought don't fit and are gathering dust now.

Also, I added 11/16 Corbin clamps ( aka tension clamps, the ones with two fingers on one side and one on the other ) to the vacuum line to the booster as it felt like they were getting a little loose. The car parts stores usually only have a variety pack with multiple sizes but Tractor Supply has them individually.

I'm going to have to get two thin nuts for the top holes in the flange as a standard size nut won't fit. I don't know if it really needs it as the other 4 bolts are pretty large but the holes are there.

[walkerb]

I drilled the top holes in mine. I bolted in though the cowl. You definitely don't want the firewall to flex