AAM 11.50 rear disk brake question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

76chevycummins · 06-09-2013, 01:55 AM

Hi I've been following this site for awhile and finally decided to join up.
I have a question I'm hoping somebody can help me with. I'm putting together a 76 chevy k 30 crew cab with a 12 valve cummins. I'm to the point where i'm ready to put in a rear end (truck was a dually when i got it). I picked up an AAM 11.50 axle for it awhile back but I'm unsure what I would need to do to make the disk brakes work with the existing brake system. I have searched around and there seems to be a lot of different opinions. New master cylinder, modify the proportion valve, or put in a pressure limiting valve. The thing is I need the brakes to work properly because the truck will be used to pull a lot of weight from time to time. I'm also considering just going with a 14 bolt with the drum brakes on it. this gives me the assurance that the brake system will work as GM designed it to. I've never had a problem with the rear drums on any of my other trucks stopping me so this idea appeals to me a lot, but it would require setting the 14 bolt up with 3.73 gears. Anyway I'd appreciate any help or opinions. ps sorry if this has been covered before.

**hatzie** · 06-09-2013, 09:55 AM

The disc drum brakes are biased differently from disc disc.
Can you get the proportioning valve from your axle donor?

76chevycummins · 06-09-2013, 02:39 PM

I bought the axle off ksl a few years ago and i'm sure that truck is long gone. The axle came off a 2003 duramax truck though so if I went to a salvage yard I could probably find a proportioning valve off a wrecked truck. Would I need the master cylinder from the newer truck to or will mine work.

clinebarger · 06-09-2013, 08:37 PM

Quote:

Originally Posted by 76chevycummins

I bought the axle off ksl a few years ago and i'm sure that truck is long gone. The axle came off a 2003 duramax truck though so if I went to a salvage yard I could probably find a proportioning valve off a wrecked truck. Would I need the master cylinder from the newer truck to or will mine work.

Late 3 channel ABS trucks have the Proportioning built in to the ABS hydraulic control unit....No use to you.

Late master cylinders use metric bubble flares.

A C3 Corvette master cylinder & a Wilwood adjustable proportioning valve would work on you truck in conjunction with AAM axle.

06-09-2013, 01:55 AM	#1
76chevycummins Registered User Join Date: Jun 2013 Location: Brigham City, Utah Posts: 4	AAM 11.50 rear disk brake question Hi I've been following this site for awhile and finally decided to join up. I have a question I'm hoping somebody can help me with. I'm putting together a 76 chevy k 30 crew cab with a 12 valve cummins. I'm to the point where i'm ready to put in a rear end (truck was a dually when i got it). I picked up an AAM 11.50 axle for it awhile back but I'm unsure what I would need to do to make the disk brakes work with the existing brake system. I have searched around and there seems to be a lot of different opinions. New master cylinder, modify the proportion valve, or put in a pressure limiting valve. The thing is I need the brakes to work properly because the truck will be used to pull a lot of weight from time to time. I'm also considering just going with a 14 bolt with the drum brakes on it. this gives me the assurance that the brake system will work as GM designed it to. I've never had a problem with the rear drums on any of my other trucks stopping me so this idea appeals to me a lot, but it would require setting the 14 bolt up with 3.73 gears. Anyway I'd appreciate any help or opinions. ps sorry if this has been covered before.

06-09-2013, 09:55 AM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 5,020	Re: AAM 11.50 rear disk brake question The disc drum brakes are biased differently from disc disc. Can you get the proportioning valve from your axle donor? __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.

06-09-2013, 02:39 PM	#3
76chevycummins Registered User Join Date: Jun 2013 Location: Brigham City, Utah Posts: 4	Re: AAM 11.50 rear disk brake question I bought the axle off ksl a few years ago and i'm sure that truck is long gone. The axle came off a 2003 duramax truck though so if I went to a salvage yard I could probably find a proportioning valve off a wrecked truck. Would I need the master cylinder from the newer truck to or will mine work.

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