K30 / K5 Frankenstein: braking problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bcoke · 05-20-2020, 10:11 AM

My braking is super touchy right now because the back drums are braking way before the front discs. Turns out I have a master cylinder, proportioning valve, and front lines for a K5, but the axles have been swapped out (owner before me) to 1 tons, which I’m guessing are from a K30.

So looks like I need to go find an MC, prop valve, and line dimensions off a K30 to match the bigger axels, right? Anyone have any advice? Or done this before and been through challenges they can share?

Any help is appreciated!

AZBuckHunter · 05-20-2020, 10:24 AM

You may just have a bad prop valve or air in the system. When I put tons on my K5 I didn't have to do anything but it was built into a crawler and not driven on the road much. An adjustable prop valve would probably be what I would do if I was going to be driving on the street.

bcoke · 05-20-2020, 10:36 AM

Yeah that’s what this one is built into (457s in the front and rear and fully rhino lined haha). Great on the trail but hell on the street, and I’ve been trying to make it more of a driver lately.

That’s a good idea, I can start there and keep doing trial and error. Any in particular that you’d recommend?

AZBuckHunter · 05-20-2020, 10:49 AM

I would get the best you can afford.
You got a pic of your rig on here?

geezer#99 · 05-20-2020, 12:04 PM

You could plumb one of these into the rear line. Put it close to the master.

https://www.summitracing.com/parts/w...hoCyywQAvD_BwE

**71blksuper4x4** · 05-20-2020, 12:11 PM

Could always run hyrdroboost.

57taskforce · 05-20-2020, 01:28 PM

Quote:

Originally Posted by 71blksuper4x4

Could always run hyrdroboost.

I agree. That and the hydraulic clutch are the two best things I’ve done to my K20. It’s really not hard to do.

WyoRoadDog · 05-20-2020, 04:33 PM

My guess, and only because I’ve been researching as part of a swap I did, is you have the wrong proportioning valve ( and maybe MC). Was it originally a four wheel drum vehicle? Disc drum needs a different PV from that, and MC should have a front chamber (disc) that’s larger than the rear (drum).

05-20-2020, 10:11 AM	#1
bcoke Registered User Join Date: Sep 2017 Location: Austin, TX Posts: 31	K30 / K5 Frankenstein: braking problem My braking is super touchy right now because the back drums are braking way before the front discs. Turns out I have a master cylinder, proportioning valve, and front lines for a K5, but the axles have been swapped out (owner before me) to 1 tons, which I’m guessing are from a K30. So looks like I need to go find an MC, prop valve, and line dimensions off a K30 to match the bigger axels, right? Anyone have any advice? Or done this before and been through challenges they can share? Any help is appreciated!

05-20-2020, 10:24 AM	#2
AZBuckHunter Registered User Join Date: Mar 2020 Location: Lakeside, AZ Posts: 45	Re: K30 / K5 Frankenstein: braking problem You may just have a bad prop valve or air in the system. When I put tons on my K5 I didn't have to do anything but it was built into a crawler and not driven on the road much. An adjustable prop valve would probably be what I would do if I was going to be driving on the street.

05-20-2020, 10:36 AM	#3
bcoke Registered User Join Date: Sep 2017 Location: Austin, TX Posts: 31	Re: K30 / K5 Frankenstein: braking problem Yeah that’s what this one is built into (457s in the front and rear and fully rhino lined haha). Great on the trail but hell on the street, and I’ve been trying to make it more of a driver lately. That’s a good idea, I can start there and keep doing trial and error. Any in particular that you’d recommend?

05-20-2020, 10:49 AM	#4
AZBuckHunter Registered User Join Date: Mar 2020 Location: Lakeside, AZ Posts: 45	Re: K30 / K5 Frankenstein: braking problem I would get the best you can afford. You got a pic of your rig on here?

05-20-2020, 12:04 PM	#5
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,716	Re: K30 / K5 Frankenstein: braking problem You could plumb one of these into the rear line. Put it close to the master. https://www.summitracing.com/parts/w...hoCyywQAvD_BwE

05-20-2020, 12:11 PM	#6
71blksuper4x4 SWB 4x4 Collector Join Date: Jun 2001 Location: Osage City, KS Posts: 5,155	Re: K30 / K5 Frankenstein: braking problem Could always run hyrdroboost. __________________ TREVOR 1970 CST swb 4x4 (speedwarning,cruise,tilt,tach,8track, original red shoulder belts,tow hooks) 1972 Jimmy (soon to be Hickey cloned) 1971 Cheyenne Super 4x4 swb (tilt,tach,buckets, original blue shoulder belts,am/fm,cruise,tow hooks, dealer 8 track) 1972 Cheyenne Super K20 4x4 Custom Camper (tilt, tach, am/fm, tow hooks, bed toolbox, aux gas tank 1972 Cheyenne Super Crew Cab K30 4x4 Duramax, Allison, np205, buckets, tow hooks (CURRENT PROJECT) http://67-72chevytrucks.com/vboard/s...d.php?t=624819 1989 V3500 Crew Cab (454tbi, NV4500, np205) 1970 Chevelle SS (LS5 454,th400,8track,buckets,tach) :2004 Jeep Wrangler Rubicon (daily driver) WTB: 1968-70 Cruise Control Lever

05-20-2020, 04:33 PM	#8
WyoRoadDog Page intentionally left blank. Join Date: Jul 2006 Location: Laramie, WY Posts: 299	Re: K30 / K5 Frankenstein: braking problem My guess, and only because I’ve been researching as part of a swap I did, is you have the wrong proportioning valve ( and maybe MC). Was it originally a four wheel drum vehicle? Disc drum needs a different PV from that, and MC should have a front chamber (disc) that’s larger than the rear (drum). __________________ There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.There is another theory which states that this has already happened. - Douglas Adams '67 GMC 4x4, 305 V6! Or all the parts for anyway... '17 Subaru Outback. '18 Toyota Tacoma TRD Off Road. '99 Ducati 900SS.



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