K20 rear brake line help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JQ-72** · 01-12-2026, 01:15 PM

Having trouble locating the correct rear rubber brake line on my 1972 K20. I’ve had guys at the parts house look up 72 K20, 72 C20, 73 C30, even some stuff up in the 80s. Everything they pull off the shelf has the smaller female ends on the distribution block - like a 1/2 ton would have. Anyone bought the correct one that I can get the part number from? Thanks

**57taskforce** · 01-12-2026, 01:34 PM

What size lines are you needing? Everything I remember messing with is 3/16 lines from the soft line fitting to the wheel cylinders. Are you trying to get 1/4” all the way to the wheel cylinders? I don’t think there’s a difference in line diameter between 1/2 and 3/4 ton or even the K30 stuff but I’ve been wrong before. Even my 1998 K2500HD has 3/16 lines across the rear axle.

**JQ-72** · 01-13-2026, 01:58 PM

All 3 holes are 7/16”

HO455 · 01-13-2026, 03:28 PM

QI used NAPA 36683 for my coil spring Burban with a 71-72 rear axle. I'm not sure but I believe the leaf spring K model hose is longer. I believe mine was 20 inches long. It has 3 -1/4" female inverted flare connections.

**JQ-72** · 01-13-2026, 07:44 PM

Quote:

Originally Posted by HO455

QI used NAPA 36683 for my coil spring Burban with a 71-72 rear axle. I'm not sure but I believe the leaf spring K model hose is longer. I believe mine was 20 inches long. It has 3 -1/4" female inverted flare connections.

All 3 female ends the same size? Every one the parts store gives me has 7/16 from the frame and 3/8 on the block. Thanks

HO455 · 01-13-2026, 07:49 PM

I recently replaced mine and the old one is still in the shop. I will go out tonight after work and verify the size of all three connections.

HO455 · 01-13-2026, 10:31 PM

All three connections are 7/16-24.

**JQ-72** · 01-13-2026, 11:54 PM

Awesome! Thanks for much for taking time to look.

HO455 · 01-14-2026, 09:35 AM

You're welcome! Just trying to help as many folks as I can. So many people here have helped me over the years. (I've got a long ways to till I break even. Thanks everyone! )

**Jason Banks** · 01-14-2026, 09:42 AM

On my 67 K20 front brake lines that has the HD front... There were no aftermarket brake hoses available. I had a local hydraulic shop duplicate the originals. They had to order fittings for one end.

So, if you have your old one, you may be able to get it duplicated.

**JQ-72** · 01-14-2026, 05:31 PM

We got some shops here that will make up hydraulic hoses and that would be my last option. I figured there had to be some reproduction ones made, just had to get a little help from the board!

01-12-2026, 01:15 PM	#1
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,746	K20 rear brake line help Having trouble locating the correct rear rubber brake line on my 1972 K20. I’ve had guys at the parts house look up 72 K20, 72 C20, 73 C30, even some stuff up in the 80s. Everything they pull off the shelf has the smaller female ends on the distribution block - like a 1/2 ton would have. Anyone bought the correct one that I can get the part number from? Thanks __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

01-12-2026, 01:34 PM	#2
57taskforce All about them K’s Join Date: Jun 2014 Location: Land of Entrapment Posts: 6,978	Re: K20 rear brake line help What size lines are you needing? Everything I remember messing with is 3/16 lines from the soft line fitting to the wheel cylinders. Are you trying to get 1/4” all the way to the wheel cylinders? I don’t think there’s a difference in line diameter between 1/2 and 3/4 ton or even the K30 stuff but I’ve been wrong before. Even my 1998 K2500HD has 3/16 lines across the rear axle. __________________ Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne: 5” lift, 35’s, front dana 60 blah blah blah… http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB: 4” lift 33”s… in a million pieces http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 35x12.5x20’s

01-13-2026, 01:58 PM	#3
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,746	Re: K20 rear brake line help All 3 holes are 7/16” __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

01-13-2026, 03:28 PM	#4
HO455 Registered User Join Date: Feb 2016 Location: Portland Oregon Posts: 12,410	Re: K20 rear brake line help QI used NAPA 36683 for my coil spring Burban with a 71-72 rear axle. I'm not sure but I believe the leaf spring K model hose is longer. I believe mine was 20 inches long. It has 3 -1/4" female inverted flare connections. Attached Images __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-13-2026, 07:49 PM	#6
HO455 Registered User Join Date: Feb 2016 Location: Portland Oregon Posts: 12,410	Re: K20 rear brake line help I recently replaced mine and the old one is still in the shop. I will go out tonight after work and verify the size of all three connections. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-13-2026, 10:31 PM	#7
HO455 Registered User Join Date: Feb 2016 Location: Portland Oregon Posts: 12,410	Re: K20 rear brake line help All three connections are 7/16-24. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-13-2026, 11:54 PM	#8
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,746	Re: K20 rear brake line help Awesome! Thanks for much for taking time to look. __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

01-14-2026, 09:35 AM	#9
HO455 Registered User Join Date: Feb 2016 Location: Portland Oregon Posts: 12,410	Re: K20 rear brake line help You're welcome! Just trying to help as many folks as I can. So many people here have helped me over the years. (I've got a long ways to till I break even. Thanks everyone! ) __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

01-14-2026, 09:42 AM	#10
Jason Banks Senior Member Join Date: Dec 1999 Location: TX Posts: 1,787	Re: K20 rear brake line help On my 67 K20 front brake lines that has the HD front... There were no aftermarket brake hoses available. I had a local hydraulic shop duplicate the originals. They had to order fittings for one end. So, if you have your old one, you may be able to get it duplicated.

01-14-2026, 05:31 PM	#11
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,746	Re: K20 rear brake line help We got some shops here that will make up hydraulic hoses and that would be my last option. I figured there had to be some reproduction ones made, just had to get a little help from the board! __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior



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