Power brake booster question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

spencra · 01-06-2006, 11:36 AM

I'm no expert on brake compatibility so here's my question.

I have a 67 SWB 1/2 ton that does not have power brakes. I also have a 67 3/4 ton with power brakes. I was wondering if I could take the power brake booster out of the 3/4 ton and put it into the 1/2 ton, I would put a new master cylinder in it of course? If I can't do a straight up swap, is there any way to make this work?

Thanks in advance for any input,
Larry

Putter · 01-06-2006, 11:53 AM

I see no reason why you can't do it. Not sure if you will actually need a NEW master cyl. though.

Longhorn Man · 01-06-2006, 11:58 AM

The P/N for power and non power brakes for the master is the same. You'd need to keep the master that is on the 1/2 ton though, becouse the P/N for C/10 and C/20 are NOT the same. I think they have the resivours swapped front for back.

**truckdude239** · 01-06-2006, 12:04 PM

should bolt right up just keep your master cylider

**53burb** · 01-06-2006, 06:59 PM

Compare the pushrod (rod in between MC & booster) needed for your existing MC. Sometimes the depth needed is different, shallow vs deep. Very obvious difference. If they are the same, all that is needed to do is, pull the MC away from the firewall, bolt in the booster, then bolt the MC to the booster & hook up full-time vacuum.

spencra · 01-06-2006, 07:10 PM

Thanks a lot guys, you've been very helpful. I didn't think that it would make a difference but sometimes when somebody is selling a booster people will ask if it is from a 1/2 ton, 3/4 ton, 1 ton, and so on. I always wondered why people asked that question. I guess I can kind of see why because if a 3/4 ton booster is rated for a heavier hauling load you probably wouldn't want to put in a booster rated for a 1/2 ton, for example. That is if that is a valid point of course, but I don't see the harm in putting a 3/4 ton booster in a 1/2 ton as long as it is compatible or could be made compatible.

Longhorn Man · 01-06-2006, 07:13 PM

The 3/4 ton/one ton booster is a daul diafram unit, while the 1/2 ton is a single diafram piece. I don't know that I have ever driven a 1/2 ton with power assist, but I do know the booster on the 3/4 and one ton is a heck of a unit.

**Bob B.** · 01-07-2006, 04:50 AM

I think it will work fine, too. You might have to mke some new lines, that dual diaphragm booster is pretty long. The difference in master cylinders between '67 1/2 tons and 3/4 tons is that the 1/2 ton has a 1" bore, and the 3/4 has a 1.125" bore. From the outside, the master cylinders look the same.

krue · 01-07-2006, 05:14 AM

You can do it with your existing lines. I put a 3/4 booster on my 70 and the only thing that wasn't long enough was the wire for the brake warning light. You get better braking with the 3/4 booster as a bonus.

Tx Firefighter · 01-07-2006, 07:39 AM

I even used a 1 ton unit on my 72. The bigger boosters give more assist than the stock 1/2 ton one does.

Like was said, there is plenty of slack in the lines to allow the booster without making new lines.

70GMCer · 01-07-2006, 08:07 AM

It worked on mine....all I had to do was use my existing master cylinder and proportion valve. Now, when I get around to changing to front disk brakes, I'll have to change the ms & prop valve.

01-06-2006, 11:36 AM	#1
spencra This, is my BOOMSTICK! Join Date: Oct 2003 Location: Berlin, CT Posts: 1,310	Power brake booster question I'm no expert on brake compatibility so here's my question. I have a 67 SWB 1/2 ton that does not have power brakes. I also have a 67 3/4 ton with power brakes. I was wondering if I could take the power brake booster out of the 3/4 ton and put it into the 1/2 ton, I would put a new master cylinder in it of course? If I can't do a straight up swap, is there any way to make this work? Thanks in advance for any input, Larry __________________ Larry Got rid of my projects for now. 1980 Jeep CJ7 1998 Nissan Sentra (my car) 2001 Toyota Sienna (wife's, of course)

01-06-2006, 11:53 AM	#2
Putter More Cowbell.... Join Date: Mar 2004 Location: Puckett, MS Posts: 3,569	Re: Power brake booster question I see no reason why you can't do it. Not sure if you will actually need a NEW master cyl. though. __________________ *There once was a member from Puckett.....Who ( fill in the blank blank blank* ) bucket**

01-06-2006, 11:58 AM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Power brake booster question The P/N for power and non power brakes for the master is the same. You'd need to keep the master that is on the 1/2 ton though, becouse the P/N for C/10 and C/20 are NOT the same. I think they have the resivours swapped front for back.

01-06-2006, 12:04 PM	#4
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,233	Re: Power brake booster question should bolt right up just keep your master cylider __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

01-06-2006, 06:59 PM	#5
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: Power brake booster question Compare the pushrod (rod in between MC & booster) needed for your existing MC. Sometimes the depth needed is different, shallow vs deep. Very obvious difference. If they are the same, all that is needed to do is, pull the MC away from the firewall, bolt in the booster, then bolt the MC to the booster & hook up full-time vacuum.

01-06-2006, 07:10 PM	#6
spencra This, is my BOOMSTICK! Join Date: Oct 2003 Location: Berlin, CT Posts: 1,310	Re: Power brake booster question Thanks a lot guys, you've been very helpful. I didn't think that it would make a difference but sometimes when somebody is selling a booster people will ask if it is from a 1/2 ton, 3/4 ton, 1 ton, and so on. I always wondered why people asked that question. I guess I can kind of see why because if a 3/4 ton booster is rated for a heavier hauling load you probably wouldn't want to put in a booster rated for a 1/2 ton, for example. That is if that is a valid point of course, but I don't see the harm in putting a 3/4 ton booster in a 1/2 ton as long as it is compatible or could be made compatible. __________________ Larry Got rid of my projects for now. 1980 Jeep CJ7 1998 Nissan Sentra (my car) 2001 Toyota Sienna (wife's, of course)

01-06-2006, 07:13 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Power brake booster question The 3/4 ton/one ton booster is a daul diafram unit, while the 1/2 ton is a single diafram piece. I don't know that I have ever driven a 1/2 ton with power assist, but I do know the booster on the 3/4 and one ton is a heck of a unit.

01-07-2006, 04:50 AM	#8
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,321	Re: Power brake booster question I think it will work fine, too. You might have to mke some new lines, that dual diaphragm booster is pretty long. The difference in master cylinders between '67 1/2 tons and 3/4 tons is that the 1/2 ton has a 1" bore, and the 3/4 has a 1.125" bore. From the outside, the master cylinders look the same. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

01-07-2006, 05:14 AM	#9
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: Power brake booster question You can do it with your existing lines. I put a 3/4 booster on my 70 and the only thing that wasn't long enough was the wire for the brake warning light. You get better braking with the 3/4 booster as a bonus. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

01-07-2006, 07:39 AM	#10
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Power brake booster question I even used a 1 ton unit on my 72. The bigger boosters give more assist than the stock 1/2 ton one does. Like was said, there is plenty of slack in the lines to allow the booster without making new lines. __________________ I'm on the Instagram- @Gearhead_Kevin

01-07-2006, 08:07 AM	#11
70GMCer Senior Member Join Date: Apr 2005 Location: Joppa, Maryland Posts: 4,408	Re: Power brake booster question It worked on mine....all I had to do was use my existing master cylinder and proportion valve. Now, when I get around to changing to front disk brakes, I'll have to change the ms & prop valve. __________________ 1997 GMC Sierra Ext 1965 Mustang



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